This article is framed as if there is something novel and profound here, but the "aliveness" of mitochondria is simply a matter of how we choose to apply the label "life" - a human linguistic construct that exists independently of the biological phenomena. This is not a new discussion - science has been considering this question for many decades, just as it has with viruses. These all come down to arguments about semantics and don't add anything to the science.
Mitochondria are fascinating and there is still a huge amount to learn about them but they are totally dependent on the cell's machinery. Most of their genes, the code for their structure, are in the nuclear DNA. A glaring omission if you are trying to make the case that mitochondria are independently living. My heart can exist independently of me, and be transplanted into other people, but does it mean that it is alive?
The implication of the whole article is that there something we have missed. This really isn't the case. Lynn Margulis's endosymbiotic origin of mitochondria was challenged by many, and it did spark a scientific debate - that's how science works. She won the argument comprehensively decades ago and is well established science. There have been many such endosymbiotic events in the history of life - there are subfields of evolutionary biology that study these processes.
> These all come down to arguments about semantics and don't add anything to the science.
This accurately describes much of science...
> My heart can exist independently of me, and be transplanted into other people, but does it mean that it is alive?
The cells that comprise your heart are very much alive, but they will die without support infrastructure. They live, they replicate, they die -- like every cell in your body. If I relocate you to the moon without support infrastructure, you would die too -- and yet (I think?) you are probably alive.
"Very much alive," in the sense of being a living organism in their own right. By that standard, each cell in the human body can also be considered a separate living organism, simply cooperating with other humans cells in a complex way. It makes sense, since we have no problem identifying the trillions of bacteria cells living on or in the human body as separate living organisms.
"Sperm and egg cells, known as gametes, fuse during fertilization to create a zygote. "
Since all humans were just 2 cells at one point. It seems to follow that the entirely of the code for what a human is, is contained in just those 2 cells.
Not just code for a finger. But even code for our deeply ingrained fear of snakes. Was just at one point contained in those 2 cells. Kind of blows your mind.
If they are separate living organisms, then there seems something recursive about humans if they can be just 2 cells at one point.
I know this is not exactly your point, but it's important to remember that it's not exactly everything. The intra-uterine environment has a serious contribution to your development, and almost certainly transplanting the fecundated cell into a different mother would lead to a different person being born. Especially when it comes to things like intestinal flora, which mostly seems to get "seeded" from the mother during birth. Even the milk you ingest after birth significantly influences certain aspects of your basic biology (mostly the immune system).
The final categorization is the least interesting part though. If we understand the origins and mechanics of how the once parasitic organism became an integral part of almost all complex life, does arguing the semantics of what label you put on it really add much value?
To reframe it: what you’re really doing is arguing about the definition of alive. In this case my opinion is: who cares. I fail to see how expanding the definition or being precise here adds anything.
> does arguing the semantics of what label you put on it really add much value
Refining the definition of something often helps provoke new understanding and tests of the limit of that refinement. It seems like a critical requirement in the "form a hypothesis" step of the scientific method.
i might be wrong but corporations/institutions never sponsor R&D in all directions so framing/phrasing is vital. but, from a philosophical pov, I agree with you.
We probably can keep a heart alive outside of body, through artificial means, for minutes, maybe hours - and I mean keep it functioning, not just chilling it to slow its death. It's plausible we'll learn to be able to keep it alive for days, months, years, decades. At which point we could say that the "supporting infrastructure" of the rest of a human body isn't necessary for the heart to be independently alive?
What if we do it all on the Moon, or Mars? How does Gaia feel about it? We already know that it's theoretically possible, if not yet achievable in practice, to create artificial environments capable of supporting human life indefinitely - or, on a long enough timescale, bootstrap an independent, self-sufficient biosphere. The two are, in the limit, the same thing anyway.
Or are we going to argue that human technology is, by extension through causality, a part of life on Earth, and therefore a part of Gaia itself? Is Gaia in all of us, and will it persist after Earth dies if humanity is still around somewhere else?
All in all, I suppose the correct definitions of terms are the ones that are most useful in a given context :). "Categories were made for man, not man for the categories", and all that.
I’m not sure what you are arguing against. For me, the article offered a lovely reminder that life is special. Life involves mechanisms but it is more than a machine. And with an attitude that our lives our symbiotically bound to another living organism (or 10^17 of them) we gain a valuable humility — one that might afford us new perspectives on how to make them all happy and flourish. That’s the promise— not just a spiritual connection to the aliveness of mitochondria, but a pragmatic orientation towards their health and wellbeing. And there is a lot of scientific opportunity to explore there.
As I said in another comment, I think that mitochondria are fascinating, understudied and a rich area for research.
We are bound to the myriad other pieces of DNA that all have different evolutionary histories within us, we are symbiotically bound to many strands of life on many levels. We are just one strand, a part of a singular whole, bound to all strands of life beyond us. This view of life led me to science. I totally think that this view of biology is not properly appreciated by most scientists.
But this article was presented as a scientific piece and made the explicit claim that mitochondria were alive which is a semantic argument that doesn't have a scientific answer.
It is a well written piece that made it to the top of hacker news and it's great to see the debate.
But it just isn't true that mitochondria are alive by our currently accepted definition of alive. This is an old debate in biology that was settled years ago. There is nothing in this paper that wasn't known to mainstream science decades ago, but it is presented as a novel scientific viewpoint.
> it just isn't true that mitochondria are alive by our currently accepted definition of alive. This is an old debate in biology that was settled years ago.
Sorry, but that’s an overreach. There are many “accepted” definitions” of life across different scientific fields. According to Wikipedia, there are at least 123 definitions of life — and there is not scientific consensus. Mitochondria are alive based on some definitions and not alive based on others.
Expecting life to have total autonomy in self-sustainability is absurd. Otherwise somatic cells or even people would be not alive.
And the argument that mitochondria are not alive because they can’t encode all their own proteins — well, I’ll point out that humans can’t produce all amino acids, either. As a thought experiment, if humans couldn’t produce a certain essential protein — and had to rely on a symbiont, would that mean humans weren’t alive?
Finally I’ll point out that Mitochondria can be healthy or flourishing — and they can be sick and die. How can something that is not alive, die?
It’s ok to argue for a narrow definition. But please don’t present this argument as though you are the defender of clear scientific conclusions. There simply isn’t consensus on this across the sciences.
I agree I didn't phrase that right. It was a short cut.
There has been debate over whether mitochondria can be called alive since at least 1890. For many years the vast majority of mitochondrial biologists have avoided the binary alive/not alive classification because there is a spectrum of 'livingness' and we can draw the line anywhere we like.
Picking a different line position is not scientific, it is semantics. What do we mean by the term 'alive'?
The article presented a profound new way of viewing the living state of mitochondria that was going to transform the world. It said nothing new, and failed to make any reference to the long term debate.
But it was a nicely written interesting article and mitochondria are going to be hugely important therapeutic area in the future.
I think they are arguing against the subtitle of the article:
"Recognizing that mitochondria are alive will open new horizons into how we learn about, and build with, biology."
Which seems a stretch based on semantics.
> The implication of the whole article is that there something we have missed.
I think this article is talking to people who haven't internalized the details of the scientific consensus. Those people are still going around, talking about "life" and making decisions based on the flawed understanding this article is critiquing. I think it's likely that the thing that "has been missed" is not narrowly scientific in the way you seem to be thinking - but more about broad implications and worldview.
I am not sure what exactly the 'broad implications and worldview' are here that are being challenged. The article is presented as a scientific opinion and references scientific research and has a doi number for citation (Cite: Liyam Chitayat. “Mitochondria Are Alive” Asimov Press (2024). DOI: https://doi.org/10.62211/38pe-75hu). What do you think that the article was challenging?
Obviously the article is challenging the view — scientific or not — that mitochondria are not living.
Side note: previously I was funded by NSF and NASA to study such questions from biophysics and astrobiology.
That said, this was a delightful read. I did not realize or conceive of mitochondria as, like bacteria in our bodies, independent living networks with unique genomes, evolution, and flows of information and energy.
Reading about the health benefits of “external mitochondria” made me think about when I hug my dog: are we exchanging mitochondria, perhaps?
> Most of their genes, the code for their structure, are in the nuclear DNA.
Are they? I was under the impression that mitochondria are closer to pseudo-cells living inside human cells.
Wikipedia seems to confirm this [1]:
> Although most of a eukaryotic cell's DNA is contained in the cell nucleus, the mitochondrion has its own genome ("mitogenome") that is substantially similar to bacterial genomes.
There's a specific page on Wikipedia about Mitochondrial DNA [1], where it is clearly said that:
In the cells of extant organisms, the vast majority of the proteins in the
mitochondria (numbering approximately 1500 different types in mammals) are
coded by nuclear DNA, but the genes for some, if not most, of them are
thought to be of bacterial origin, having been transferred to the eukaryotic
nucleus during evolution. (citing [2])
See below on Wikipedia: "Most proteins necessary for mitochondrial function are encoded by genes in the cell nucleus and the corresponding proteins are imported into the mitochondrion. The exact number of genes encoded by the nucleus and the mitochondrial genome differs between species."
Yea I would def. not call mitochondria "alive" since they are so deeply integrated with the rest of the cell & vice versa.
mito is like <100k bp vs 3000000k bp in human genome (bp = base pair = "character" in a string)
principle derives from the concept of "the selfish gene" or "the red queen" these famous books on the topic. Arms races between X and Y chromosome. Arms race between nucleus and mitochondria, and so on.
or put it this way. why do all animals have sex? because it generates gene sequences that confer fitness more efficiently than self-replication (which is the typical repro method of unix programmers)... .. generates such gene sequences for NUCLEAR DNA that is, mito DNA comes from mom only (the red queen.. .. "mitochondrial eve" ... "y chromosomal adam".. etc). and thus the mito is fundamentally unable to wield the power of evolution, completely evolutionarily outclassed by those nuclear chromosomes. thus exporting all its genes to the nucleus, conferring advantage to all such progeny with their superior power supply
I don't understand this definition of "alive". Isn't every cell in my body alive? There are definitely differences between an alive cell and a dead one.
> There are definitely differences between an alive cell and a dead one.
Energy flow is the difference. but then everything has an energy flow. Losing and gaining electrons. So it is possible that literally everything is alive, don’t you think? Maybe the problem is is that we’re trying to make a definition where none ultimately really exists.
what about obligate intracellular parasites like mycoplasma? They are awfully close to mitochondria but we think of them as alive. They've lost many of their genes and can't survive without the host. Looking at those, you could almost see a path from an obligate intraceullular parasite to an organelle derived from a phagocytosed prokaryote.
But it does. How many grains of send form a heap? How many atoms form a fluid? Is it something a particle or a wave? The line can be drawn depending on specific problem, on how useful a heap/fluid/particle/wave model for this specific application.
A label (abstraction) allows us to bring corresponding tools that were developed for it. If you can count trees then the same math can be useful to count people.
Arguing about where you draw the line doesn't advance anything, it just muddies the water. We have robust definition of what is and isn't alive built by consensus. Mitochondria fall into the 'not alive' category by our definition. Presenting decades old scientific views as evidence that this categorisation is wrong doesn't add anything. This article has had far more exposure than some really groundbreaking science and it adds nothing.
This "aliveness" debate reminds me of the "11.000 years old dog". Basically a tumour that has been spreading from one dog to another for thousands of years.
> My heart can exist independently of me, and be transplanted into other people, but does it mean that it is alive?
Your heart cannot exist independently of you as a heart. It is only a heart in name, as it does not function as a heart. Its identity as a heart depends on its ability to function as a heart within some organism. The same can be said for any part or organ. A severed hand is a hand in name only. A corpse is not a body, as it no longer functions as one.
A transplanted heart becomes a heart once more. A reattached hand becomes a hand once more. If you think this is weird, then you haven't done your metaphysical homework. Why should it be weird? It could only be weird if you have made certain (unexamined) metaphysical presuppositions. The structure of a heart removed from an organism persists long enough that it can become reintegrated into an organism such that it functions once again as a heart.
But also note that the matter composing a heart itself isn't fixed. About 1% of heart cells are replaced per year in the young. So if function and structure can survive transient material change, and the matter that makes up a heart can assume and lose and reassume its identity as part of a heart, then why can't a heart lose its identity as a heart when removed, and regain its after it is implanted back in?
> There have been many such endosymbiotic events in the history of life - there are subfields of evolutionary biology that study these processes.
Exactly, if mitochondria is alive then so is chloroplasts and who knows what else. The line needs to be drawn somewhere, also life and death isn't as clear-cut as many used to believe
I think questions like this make science fun for the uninitiated because it represents both the uncertainty and the intense investigation and evidence discovery process involved in tearing hazy things and recovering concrete truths in the process
Can you elaborate on this comment? What should popular biologists like Michael Levin be saying on every podcast/interview and why? Serious question from someone who is familiar with Lynn Margulis but not Michael Levin.
I don’t disagree with your take. The concept of the semantics of “what is alive?” has been going on for a long while now.
Have you considered that this is a more formal version of a Bill Nye science explainer, but for adults?
The reason I say this is that while unintended (I think) your post has a, “of course they’re alive, we’ve known this forever” vibe, which can inadvertently come across as condescending.
I don’t mean to pick on you, we’re all guilty of such speak when we deem concepts to be obvious or well known.
Your post reminds me of the “1 in 10,000” XKCD comic:
I agree with you, which is why I wrote this- but if you google "are mitochondria alive" gemini says it isn't. And yes, the cells in your heart have an effective and potenitial niche!
We seem to have many tools to engineer viruses, but few to engineer mitochondria- perhaps considering them as alive could change that!
I am not sure you should be relying on an LLM as any indication of anything...
More seriously, considering something as being alive in order to engineer them better does not necessarily change the fact of them actually being alive or not, in my opinion.
If LLMs work the way I understand them to, they are trained on large corpora which contain a statistical preponderance of statements which are consistent with the current scientific mainstream, so it may not be completely crazy to try doing this; you'd get the scientific mainstream explanation, and possibly a few alternative hypotheses if they had enough literature support.
Why would it be consistent with the scientific mainstream? Unless there's evidence that scientific reports and material are specifically up-weighted during training and prioritised somehow, whatever an LLM says will be only consistent with its training material, which could have any proportion of fake articles, Reddit posts, Quora responses, encyclopedia pages and joke blogs
> which are consistent with the current scientific mainstream
This seems to require a high amount of curation of training inputs, but I haven't done real digging into it, just going off the more casual "all of stackoverflow" or "all of reddit" type comments frequently thrown around. But if there is such a curation I'd agree, I just don't think there is that curation.
Eukaryotes generally can’t survive without mitochondria either. It seems silly to discuss if different subsystems in a living organism are independently “alive.” It’s a bit like arguing if just the wings or just the engine of an airplane are flying machines.
You are completely right that we should be thinking far more creatively about manipulating mitochondria. There are a lot of diseases (including Covid) that have mitochondrial aspects. I just don't think calling them alive helps, other than to get you some decent exposure on HN :)
In Earth’s history, mitochondrial endosymbiosis occurred once. Without that you don’t have the energy budget for complex life. Moreover, there may be a narrow window where it can happen: modern microbiology has defences and selection pressures that it make inhospitable to the hobbling chimeræ the first mitochondrial cells would have been.
Until mitochondria, the emergence of life from nothing is plausible. With mitochondria, its progression to complex, multicellular and intelligent life makes sense. Both processes in small steps can be replicated, more or less, in the lab. But that one moment is not and has not been. As a result, I think the universe has lots of living slop but very few plants and animals.
This process, known as primary endosymbiosis, happened at least twice, for mitochondria and chloroplasts. Further, while all chloroplasts (and more widely plastids) appear to share a common ancestor, there is evidence that mitochondria may descend from multiple lineages that underwent lateral gene transfer and/or convergent evolution. Nitroplasts are a likely another, separate instance of primary endosymbiosis.
There is also secondary endosymbiosis, where the endosymbiont organelles of one eukaryote are engulfed and incorporated into another eukaryotic cell to create a new type of endosymbiont. This has happened at least 8 times.
There are also theories that some other organelles are the product of other endosymbiosis events, many of which also have some of the hallmarks like their own genetic material. These theories are more speculative though.
It's also worth noting that while eukaryotes obviously gained some important capabilities from incorporating these endosymbionts, the endosymbionts they incorporated obviously managed to just evolve to perform those functions directly. Further, while one of eukaryotes' distinguishing features are mitochondria, there are several other major differences, and mitochondria are not believed to be what made eukaryotes better able to evolve complex multicellularity. Prokaryotes have indeed evolved multicellularity dozens of times, and we arbitrarily set our definition of complex multicellularity to distinguish from what prokaryotes have achieved.
The first time it happened involved a huge number of changes in the host cell, like the creation of a nucleus. That makes it seem more likely that an already eukaryotic cell can more easily incorporate other endosymbiotes.
Observation of prokaryote/prokaryote endosymbiosis would be real evidence against the rise of eukaryotes being the or one of the main limitations in the number of intelligent species in our galaxy.
There's really only one change that mattered - phagocytosis. The ancestor of all was a prokaryote that practiced phagocytosis, the process of engulfing other cells. Endosymbiosis resulted from some of these engulfed cells not being digested.
There are no known modern prokaryotes capable of phagocytosis. Presumably the extinct prokaryotes who were capable, including those from the same lineage as the eukaryotes but which did not pick up mitochondria, were outcompeted by the eukaryotes who occupied the same niche.
Other changes like the origin of the cell nucleus and many other organelles can be readily explained by other malfunctionings of the phagocytosis process. Basically once you have the ability to pinch off parts of your cell wall into internal structures, you suddenly get a bunch of internal structures made of stuff that look surprisingly like cell wall.
In addition to what others have pointed out (chloroplasts), I think this makes another mistake. Although only the mitochondria and chloroplast lineages remain, it is possible it happened other times but those lineages were out-competed, for whatever reasons, and are now extinct.
> it is possible it happened other times but those lineages were out-competed, for whatever reasons, and are now extinct
Chlorophyll probably outcompeted retinal [1]. (The stuff in our eyes.)
The reduced form of my claim is that mitochondrial life so freakishly outcompetes its competitors as to be in a class of its own. Which still yields a rare Earth, albeit a first among many.
In an evolutionary process, one lineage running away is the most likely outcome. It's very unlikely that two competing lineages would evolve to be exactly equal at the same time and remain equal for an extended period of time.
It's based on the fact that one explanation of why there's not even millions more species of all life, is because the more successful ones simply cannibalized the less successful ones. This would've started even before complex life, almost at the chemical level.
I say cannibalized, because avoiding eating your own species is a higher brain function that would've came far later, so it came down to eat or be eaten. Still is frankly.
>I say cannibalized, because avoiding eating your own species is a higher brain function that would've came far later,
Two convergent intuitions as to why this is true, but for the wrong reasons:
Species (maybe only [di?]morphic ones) rarely kill other instances of their own species, only maim - usually to the point of socially/reproductive shame/selective behavior; as infra-species violence is usually done for sexual signaling.
Like squirrels neutering each other, giraffes ruffling neck-fights, etc, it is not generally advantageous to actually hurt the opponent more than needed to signal dominance in a social hierarchy - this "gentleman" agreement is similar to all emergent collusion behavior exhibited by "free agents" in a limited pool; even without communication, the self-interested incentive to all follow a convergent rule will eventually emerge. Whether it be price fixing, social norms, or any other system where partially-regulated complex systems compete.
Additionally, for cannibalizing to be a positive-selective-trait, the species would had either adapted to eating the liver - the "resilience/filter" of a system, or had been "lucky" enough to identify/delineate/get repulsed by it.
Eating your own species liver would be nearly self-defeating-ly impossible from an evolutionary point of view and avoiding it but still eating your own species is too "taboo" (evolutionary artifact) of a benefit to ever randomly stumble into, especially against the benefits of 'good-sportsman-ship'.
> it is not generally advantageous to actually hurt the opponent more than needed to signal dominance
It is advantageous to beat a rival and take their energy even within a species. That's part of the whole 'survival of the fittest' thing. Preserving them for cooperation or something like slavery happens, but it's a rare strategy specific to intelligent animals like the GP implies.
As Dawkins points out in `Selfish Gene`, it's the DNA sequence that's the evolutionary entity. For example, all mothers (and most fathers) protect their young even though it's a food source. Eating your own species (even children of other mothers) is counterproductive for the DNA itself, despite being productive for the particular copy of the animal doing the eating.
>reserving them for cooperation or something like slavery happens, but it's a rare strategy specific to intelligent animals
Exactly, GP thinks this is a higher order behavior.
I should had clarified, this is lower, more intuitive behavior. It is not, which is why it arises emergently in lower-complexity/class systems.
>beat a rival and take their energy even within a species
Beating a rival and taking their energy is awesome!
And if done with literal, figurative, social, and complex "CLASS", it is literally sexy too!
National Geographic is entertaining for many dimensions of reasons.
Actually dismembering your sexual-rival and literally consuming their poor caloric conversion is pitifully inefficient compared to making them a sub-ling, whether it be via hen-pecking or innate dominance. It made sense before sexual dimorphication (moreso), but less so now.
Ladies like a gentleman, and gentleman's agreements are literally non-colluding emergent behavior to abide by unspoken higher-order rules for one's own explicit conscious self-incentive (lower order, high entropy), but also the implicit collective unconsciousness incentive (higher social order, lower entropy)
Both are reslience traits, which only emerge when selected for.
I have no idea what you meant by liver. Maybe it's a biology term I'm unaware of. Certainly you didn't mean the organ. lolz.
Anyway, an interesting point about evolution is that things had to have been eating other smaller things long before the brain had enough processing power for "Species Recognition". It would've initially been a simple brain and rod/cone eye neuron and motor neuron in a fish that executed primary the rule of "See movement then execute tail wag, open mouth, close mouth" in that order. It takes like 5 neurons wired in a specific way to accomplish that. The first neurons had to have been that simple. Indeed the chain reaction of "input photon and convert energy into motor neuron charge potential" had to have been the actual chemical process that eventually developed the first neuron to begin with.
It was only after MUCH more evolution that avoidance of eating one's own species would've been possible by visual inspection of the prey. However, it's true it could have been a 'taste' signal where the scales of your own species had a bad enough taste that you spit it out rather than eating it, and that can be accomplished also with a brain of only a few neurons.
Liver/kidneys are organs where toxins are filtered, from the prey the predator consumes.
I am not a biologist obviously.
Because of the "food chain" actually being a pyramid, those organs contain the same "toxins" that are to be avoided, exponentially accumulating in whatever "organ" had the function to add resiliency by storing these toxins.
Oh, I see. You expected people to infer "toxins" from the words "resilience/filter". Got it.
However, liver eating is a moot point regardless, because evolutionary theory would suggest eating toxins would have a bad taste/smell, so that organ would simply be avoided, while eating the rest. So it has no bearing on whether cannibalism happens or not.
>However, liver eating is a moot point regardless, because evolutionary theory would suggest eating toxins would have a bad taste/smell, so that organ would simply be avoided, while eating the rest. So it has no bearing on whether cannibalism happens or not.
yes, this is why evolutionary theory is the softest of hard sciences and the hardest of soft sciences.
We have nothing but confirmation bias and little time to test anything macro.
However, we do have contra-positives and the like; in this case, we (ourselves) avoid Liver in some animals, and notice the M.A.D-avoidance agreement among more socially-complex systems.
You shouldn't eat your young, you should eat your rival tribes young.
Especially because the young hand't accumulated much toxins yet, relative to the adults. And it is easier to bash babies over rocks than grown adults.
yes, Q.E.D; the ambiguity of our lingua franca can be an "accumulate toxin" of sorts when trying to articulate higher-order ideas, as words (especially used as analogies) can carry implicit deprecated weight, and without the resilience of good-faith inference, can lead to misunderstandings, mis-alignment, or walking/talking write/right past each other.
--or-- yes, when someone writes a very unclear sentence and then blames the reader for not understanding it...even going so far as to accuse the reader of bad-faith motivations.
>>> ...for cannibalizing to be a positive-selective-trait, the species would had either adapted to eating the liver - the "resilience/filter" of a system, ...
>I have no idea what you meant by liver. Maybe it's a biology term I'm unaware of. Certainly you didn't mean the organ. lolz.
>writes a very unclear sentence and then blames the reader...to accuse the reader of bad-faith motivations....
How would I know my reader would had misconstrued my "unclear" (read: perfectly grammatically specific) intentions a priori?
Did we both edit our posts....to improve accuracy, increase resiliency, and to compete ideas?
You edited your post after first insulting me, then deleting the insult. Yes I saw it, but I removed my acknowledgment of the insult, only after you removed the insult. But you weren't done yet...just taking care not to have "flaggable" wording. Now it's more stilted language and Latin FTW. Did I miss anything?
neither of us had the incentive to either acknowledge our edits nor call the other out,
nor face the (perceived, social, higher-order) dissonance of being slightly unclear or "wrong" due to our own ego/self-interest (conscious, lower ordered self);
the emergent behavior then (gentleman's agreement) was to preserve our own ego's and not call out each other edits - which most people would never do, because:
our slightly varied ideas compete more fiercely for the same finite pool than other, completely niche-unrelated abstractions.
we are 4 layers deep now, but ill reduce for conciseness (for lurkers fwiw)
dont shit where you eat <- evolved trait to avoid waste-by products
dont hit a man when he's down <- highly effective altruism is still beneficial
morality is cowardice <- ties this all together from highest order (ego) to the id (fear of being replace)
And now back to reality: I only edit posts to add an important point or fix a typo, but you edited your post to remove the insult it initially contained.
The insult was my inference that we should assume good faith, and that you had not done so (provably, by your 'lulz' snark); which you clearly did not show when assuming something other than the "liver" would be a organ of filtering toxins.
A decently display of faith should at least warrant a re-parsing of my (actually perfectly unambiguous) grammatical clarity, of which you implied was less than so.
Warrants the question, why not admit my posit:
That slightly-varied entities competing for the same/similar finite/limited supply pool of resources/demands will tend towards -- as an emergent behavior of both short-term disorderly self-incentivization and the stochastic long-term higher-order unconscious collective collusion -- the tendency to compete until dominance over **reproductive** rights are secured, but no more. The more fiercer the competition, the more selective the sieve, the more the dominant traits propagate: up to a plateaued point. Further complexity/order can than be more efficiently achieved by lessening the furiousity of the competition to a point of cooperation, which then innately lends itself to more hierarchy, efficient use of energy.
People aren't intimated by people that cannot replace them, they are by people that can.
Take it from Roko the Replacer:
According to Sigmund Freud's psychoanalytic theory, the "fear of being replaced" is most closely linked to the concept of "castration anxiety," particularly within the context of the Oedipus complex, where a young boy fears his father will punish him for desiring his mother by castrating him, essentially rendering him "replaced" in her affections.
But somewhere between a middle school drop out and a super-intelligence and 5-layers QED, I think my posit has merit.
Free to continue discussion; but the under the Ego lies the Id, and I'm not well versed in that science yet, still approximating.
The crux of the misunderstanding was that you assumed any reader would know a reference to liver is a reference to "toxicity" apparently based purely on the nearby words "resilience" and "filter". That was a flawed assumption, and ambiguous unclear writing.
The success of birds, bees, trees, plankton, mammals and so on. Many life forms have been rendered obsolete when the right adaptation comes along and forms a new branch.
We don't know the fundamental energy requirements of complex life. The threshold may be 2%. It may be 19.995%. If non-mitochondrial metabolism is common, the Earth would still be rare in that we'd be the "fast" biosphere. The high-octane species. Given how power-intensive intelligence is, that might be material. (Or it might not.)
More fundamentally: we have no plausible alternate chemistries that don't bootstrap on mitochondrial life. (We do for photosynthesis.)
I’m not convinced there’s a reason to think intelligence is inherently power-intensive. Based on our limited samples, it’s certainly energy intensive, but there’s no reason it couldn’t be slowed down. In a world with less power available to life, one would expect speeds of e.g. predators and prey to be slower, allowing a slower intelligence to still provide an advantage.
> Sure. But we know it empirically is. Our brains are expensive.
But our brains have mitochondria. As do our prey, and our predators. Is there any reason to suppose that the absence of mitochondria implies less potential for intelligence, instead of the potential for equal but slower intelligence? Mitochondria are about power production, not energy production -- they are a very dense source of ATP, but the reactions they use would provide equal energy even if less concentrated.
I don't understand why anyone would commit to so adhering to a speculative hypothesis H as to call themselves an "H-er", especially one so pointless and vague as "Rare Earth". There is some probability that a random star has intelligent life on orbiting planets, but we have no idea what that probability is. The original "Rare Earth" proposal suggested that the Earth may be the only such planet in the galaxy, but at that rate there could be hundreds of billions of Earths.
> There is some probability that a random star has intelligent life on orbiting planets, but we have no idea what that probability is.
100%. The evolutionary pattern of our solar systems formation and earth ending up, temporarily, in just the right spot isn't rare but (was) a matter of time/timing.
Now one could argue that the stellar objects carrying specific components necessary for life did not hit every or many solar systems but every single simulation (in my head) of the big bang's aftermath reveals that it's at least multiple hundreds of thousands, given how much the observable universe has revealed so far in the places that we looked.
Mitochondria seems to have been an 'accident', yes.
That does not mean that other lifeforms in different planets require mitochondria or equivalent organelles. As long as they can perform the necessary chemical reactions (which could be different in a different environments) and extract enough energy, they should be good.
How did mitochondria evolve in the first place? Could they have remained as independent organisms and use their massive energy budget to evolve independently?
> long as they can perform the necessary chemical reactions
That mitochondria are conserved as an independent organelle across almost [1] all eukaryotes, across billions of years of history, suggests this is something the nuclear can’t easily in house.
> other strategies were just out competed by this one and lost the opportunity to develop further
Absolutely. It also means--however--that any niche where alternative did exist, when exposed to mitochondrial life, they lost.
Now that I think about it, it would be pretty funny if we're this universe's cheela [1], a freakishly overclocked biosphere that runs faster not because it had to but because it happened to.
Evolution is path-dependent. Notice that mammals were comprehensively outcompeted by dinosaurs till asteroid removed them and gave mammals time and niches to develop in. If you recreated dinosaurs right now they would lose to mammals (for example to homo sapiens).
It's perfectly possible that mitochondria are the dinosaurs of "cell powerplants" that just haven't encountered the asteroid to let other (ultimately better) solutions develop.
>It is the first eukaryotic genus to be found to completely lack mitochondria, and all hallmark proteins responsible for mitochondrial function. The genus also lacks any other mitochondria related organelles (MROs) such as hydrogenosomes or mitosomes. Data suggests that the absence of mitochondria is not an ancestral feature, but rather due to secondary loss.
Absolutely fascinating. Especially the exotic multicellularity part. Maybe if it evolves even more multicellularity it will struggle with cancers of its own and have to reevolve tumor suppression, wouldn't that be something?!
The benefit of mitochondria is in the isolation of the high power reactions, that involve chemically aggressive elements, from the rest of the cell. That allows for high energy throughput without self damage. Cells that do not have mitochondria run the same or analogous power producing reactions, but at a much lower volume, to keep the damage sustainable. An alternative option to mitochondria would be to evolve some means for isolation of the power production.
Mitochondria are bacteria that were endosymbioticized into what became the eukaryotic cell.
Mitochondria can still survive (live) independently and functionally in the blood when they're separated from platelets and microvesicles.
Mitochondria are the software that epigenetically switch nuclear DNA genes on and off. That sofware can be tweaked by light, for instance UV light or IR light.
mtDNA mutates x1000000 more rapidly than nuclear DNA.
> Being obligate intracellular bacteria, rickettsias depend on entry, growth, and replication within the cytoplasm of living eukaryotic host cells (typically endothelial cells).
> Most notably, Rickettsia species are the pathogens responsible for typhus, rickettsialpox, boutonneuse fever, African tick-bite fever, Rocky Mountain spotted fever, Flinders Island spotted fever, and Queensland tick typhus (Australian tick typhus).
One interesting thing is that many reactions actually have to occur in their own compartment- and since we have not lost the mtDNA, it may suggest that having an additional control center is beneficial.there are some interesting theories about the relations of that to lifespan https://www.cuimc.columbia.edu/news/mitochondria-are-flingin....
It's more that cells can have large numbers of mitochondria than that teach produces a large amount of power. Prokaryotic cells can grow large, but because they respirate over their surface they are energy limited.
Mitochondria allowed who different energetic regimes and structures. Like the scaffold that allows multicellular organisms to even hold together simpler are not possible (energetically) without mitochondria. It took the whole marriage of the two systems to allow the energy state (the "chemical reactions" as you say) to be possible
SFI Complexity podcast has a few great episodes on this
It’s so pathetic to keep hearing that dna is an accident , life is an accident, mitochondria is an accident. What is an accident that natures says “oooops”. When will we take our heads out of the sand and realize the universe is alive and creating everything. There are no goddamn accidents !!!!
What? When saying that "X" is an accident, nobody means "nature says 'oooops'. Nature is neither conscious nor alive, if universe were alive and creates and shapes life, why is there so many errors happening in the universe?
Everything exist by " accident", and that means that is the result of random events that happen unexpectedly in unimaginable places, leading to an environent were the outcome of this events causes more random events.
Why universe insist in making life so uncommon if it has the secret to create and replicate?
Like other gradients (heat, pressure, chemical) it might seem rare, the gradient guides its occurrence. A power efficiency gradient was going to happen eventually, accident or otherwise.
I may be wrong, but I recall reading recently it had been found the same event had occurred again, fairly recently (hundreds of thousands of years, could be millions) in some species of bacteria or something like that.
Here's a thought, also; maybe once this has happened, it tends to crowd out needing to happen again.
Huh. This is the correct news, but a different article to the one I recall. However, very interesting;
> The first occurred about 2.2 billion years ago, when an archaea swallowed a bacterium that became the mitochondria.
> The second time happened about 1.6 billion years ago, when some of these more advanced cells absorbed cyanobacteria that could harvest energy from sunlight.
> And now, scientists have discovered that it’s happening again. A species of algae called Braarudosphaera bigelowii was found to have engulfed a cyanobacterium that lets them do something that algae, and plants in general, can’t normally do – "fixing" nitrogen straight from the air, and combining it with other elements to create more useful compounds.
So, tremendously rare, at least to our knowledge at this time, but not a one-off.
And even if those hadn't become organelles, who knows if they (or mitocondrias) could have evolved towards multicellular life on their own? They were already organisms to begin with.
All planets with a diverse chemical makeup will stumble across accidental formation of a replicator molecule. It's 100% certain. That's all that's required for "life".
People have theorized even a 50 base pair segment of RNA might be capable of building exact copies of itself, either by snapping in half and auto-forming the same other half, or by other means. Since there's two sexes, it was perhaps a "halving" at that level, that early on, which led ultimately to TWO sexes, but that's a side point.
We can even predict the probability of any 50 base pair ordering. It's 1/(4^50). That's 30 zeroes in the denominator. Now consider that a single glass of water has 10^23 molecules. That's 7 orders of magnitude difference. So the amount of water you need to cross that magnitude threshold is 7. Turns out that's exactly the size of an Olympic swimming pool. 10 million cups of water.
So statistically, a planet with an ocean volume only as large as a swimming pool has the "Statistical Power" (power of large numbers) to find ANY 50 base pair combination (give or take an order of magnitude or two) Once it finds a replicator, life has started, and so has evolution. And that's guaranteed within the first minute or so, at reasonable temperatures. Now multiply that time by the average age of a planet, and you begin to realize, statistically life is guaranteed, in any chemically diverse scenario with reasonable temperatures.
Interesting argument, but nobody believes that a diverse chemical makeup is sufficient to guarantee life.
You can wave big numbers around but none of that makes a convincing argument; it's not hard to construct any number of scenarios where self replicators are started but don't lead to true life.
Also you're comparing a gram of water to a bunch of bases; H2O is not DNA.
Sure we don't have proof that all life will form from essentially "binary" data, (although technically ours is made of 4 bases, not 2), but it's almost axiomatic that life will find the simplest possible way to store information before it finds the more complex ways. Ergo DNA is almost binary, but quarternary instead. It's nearly digital.
Insofar as your H20 vs DNA comparison, I merely used water as a way to show relative "scale". That is, HOW MUCH fluid volume (relative to the order of magnitude of size of atoms) would it take to contain the requisite number of RNA. Because when it comes to probabilities of finding astronomically unlikely combinations, astronomically large numbers is key. I think in a mole of random Rubicks cubes, hundreds will be "accidentally solved" (I forgot those numbers, so check my math, on that one)
The reason I threw in the "give or take 2 orders of magnitude" caveat was precisely because I knew someone like you would accuse me of relating H20 to RNA in a way in which I didn't. Other planets will have different atoms, not necessary water-based life, but planets even the size of a swimming pool have the "numbers game" power to create life.
Are you aware that at high concentrations, DNA, RNA, and proteins all have serious problems? For example, DNA and RNA are highly charged, with strong repulsion effects, while also having large greasy areas. At the concentrations you're describing, the DNA and RNA would not be functional as we know it.
Right. The "thought experiment" math is a tight packing of theoretical RNA molecules, and not intended to be taken literally, without a dilution factor; but only to show [some] people their intuition is WAY off about the power of large numbers to "create" unlikely patterns.
For example, if you ask most people how many randomly occurring Rubiks Cubes will just be accidentally solved even with Avogrdro's number of them, their answer is usually zero; and unsurprisingly they're the same ones claiming there had to be a God to create even the initial replicator.
For this to hold, each of those water molecules in that swimming pool needs to somehow turn into a random 50 base pair chain of RNA.
Those RNA molecules are also going to be ~two orders of magnitude larger than a water molecule, so you're going to need a bigger pool...
To actually replicate, some loose ingredient molecules must also be present, and in reasonable quantities to be at hand in any given place in the pool.
The argument you are actually making is that a vessel that is filled with randomly assembled chunks of RNA not shorter than 50 base pairs each, the quantity of which equal the number of molecules of water in an Olympic pool, would contain life with probability ~1.
Now, the ocean is large, and a billion years is a long time, but I'm a long way from convinced that the chance of life is 100% on any given suitable planet.
That's a decent analysis of the things this "thought experiment" doesn't address. I'm not a chemist but I think in a sea of AT and GC pairs even mixed with water, the ability to find every random sequence possible is near certainty:
Especially when you multiply by the number of swimming pools of all ocean water (10^14) by the number of minutes of the history of Earth (10^15), and consider that the probability of the accidental 50 base pair replicator forming needs to have those 29 extra zeroes, in the numerator (not the denominator). So the likelihood, now that I add more info, has just gone up 29 orders of magnitude. lol. (BTW. the 1 minute assumption will be temperature dependent, and is a guess at how long it takes reactions to take place).
The whole thing is a rough approximation like the Drake Equation is, and each number is an estimate. If you want to attack the Thought Experiment, at it's weakest point, just question the initial assumption, which is the biggest guess of all, that some unique 50 base pair RNA can replicate itself.
There are a huge number of different organelles that evolved independently through events like this- other people mention chloroplasts but there are many others, and probably many yet undiscovered.
I would argue that the type of event that produced mitochondria is likely not rare at all, but certain pairings will so outcompete others that we should expect only one to survive and dominate.
> Moreover, there may be a narrow window where it can happen: modern microbiology has defences and selection pressures that it make inhospitable to the hobbling chimeræ the first mitochondrial cells would have been.
I don't think it is a very persuasive argument, because it is possible that modern microbiology has defenses because it has mitochondria. I know almost nothing about cells from a few billions years ago, but it seems plausible to me that they were ambivalent towards intrusions of other cells, it can be beneficial or disadvantageous depending on an intruder. Moreover beneficial intruders could give a lot of evolutionary advantage, not like today, when all important things (like mitohondria) are already here. In theory, bacteria could benefit a lot, but there are no ecological niches for a bacteria with mitochondria, all are claimed by some eucaryotes, which are highly adapted.
It is a very common thing in evolution. For example, there are bats, but they cannot evolve and replace birds, because there are birds. Bats have their niche, but they cannot outcompete birds at being more birds than birds. If they were given a chance, then maybe they could try to catch up with birds, but they didn't have a chance and they will have it only if some cataclysm will wipe out birds and leave bats.
Not everything. Life in particular. Because without life (a conscious observer) reality cannot exist. So it should be a property of reality for life to emerge.
Isn't that kind of mixing up the chain of causation? Without a winner, a lottery cannot exist (or at least, at p=0, it's nonsensical). That doesn't automatically imply there are a lot of winners, however.
I think what I am trying to say is consciousness (life) is reality. And so all kind of planetary experiences can exist inside consciousness as it's contents since consciousness is capable of generating all kind of content.
There is nothing specific about our consciousness that makes it unique to earth.
Your philosophy is consistent with panpsychism (https://en.wikipedia.org/wiki/Panpsychism). Not really clear how this affects the major discussion here, which is about objective reality as determined by science, and so far as we can tell, neither life nor consciousness is not a prerequisite for reality. It's a fun idea to play with but firmly outside the realm of something we could experiment with scientifically.
"Mistaking the map for the territory is a logical fallacy that occurs when someone confuses the semantics of a term with what it represents. Polish-American scientist and philosopher Alfred Korzybski remarked that "the map is not the territory" and that "the word is not the thing", encapsulating his view that an abstraction derived from something, or a reaction to it, is not the thing itself. Korzybski held that many people do confuse maps with territories, that is, confuse conceptual models of reality with reality itself."
Okay. I can see that in day to day life. People confusing sentences with actual knowing. Like labeling something a tree and thinking you know what a tree is because you know it's a "tree".
But how did anyone verify there is an underlying reality outside consciousness? It's just an assumption right?
Yes, it's taken on faith by scientists that we live in an objective universe with cold hard reality outside our consciousness. It seems like a reasonable assumption, consistent with all our observations. It seems not unreasonable to assume that in the early universe there was nothing living, then at some point, through random chance, the first living things became alive (possibly from some non-alive replicators), and then later, the first living things with consciousness came to be. Again, all of this is consistent with our observations, but effectively taken on faith/treated as an assumption.
There is no known scientific principle or theory with experimental support that without a conscious observer reality cannot exist. It's not something that can be tested, and lies in the realm of philosophy, not science.
Only if you assume it went the seemingly straightforward way, but it could have been more complex. Maybe at first there was no particular limit to unicellular life, and there were unicellular lifeforms both small or large. But the big ones had a terrible problem avoiding getting parasitized by microscopic ones. As, there is one wall to breach, and once it gets in, it's in for good. So maybe eventually one of the bigger ones developed multicellularity as a kind of internal defence wall system, rather than multicellular life evolving from tiny cells clumping together. This gave it an enormous advantage at larger sizes, as all pathogens had to invade the cells one by one, and most of the macroscopic unicellular organisms perished, and some unicellular eukaryotes evolved since then.
There are a lot of sub Neptune planets, the reason why there are only a few earth alike planets is just lack of powerful telescopes and observation time. As technology improves, we’ll find much more planets like ours. Earth is not unique in any way
We don't. But we know we can't replicate it, have never observed it, don't seem to find half-assed attempts at it in the wild and that there weren't multiple competing chemistries that found themselves co-existing, there was one.
I know nothing about biology, pardon my ignorance. From the article it sounds like mitochondria were a separate organism that has perhaps simplified through specialization and is currently on the boundary of being an independent life form. It also sounds like there are other structures (golgi apparatus are mentioned?) which are not on the bubble. Are we sure that there is not an arrow of time here, where once those other structures were also semi-independent and have become less so?
More broadly, it leads me to wonder whether cellular life might eventually/might have at some point specialize towards hosting novel endosymbioses.
Either scenario, assuming what I'm saying isn't just total nonsense, would seem to make the state of mitochondria less of a one-off event and more of the instance of that event we are around at the right time to observe.
Those other membrane bubbles inside out cells don't have any of the machines we expect to be associated with cellular life- but you never actually know!
The astrobiology schtick is just a what if thought experiment though, and nothing proven nor claimed to be fact. It's just a way to show that the scale of the universe is "hugely, mind-bogglingly big" while trying to pull a number that our squishy lobes could comprehend. If 1% of mind-bogglingly huge number, then 1% of that, then 1% of that yields a still mind-bogglingly big number. The laws of large numbers would suggest something as well. Otherwise, "its an awful waste of space"
This article managed to hit two classic science journalism cliches in just the first few paragraphs.
(1) “Someone hypothesizing a very dramatic theory with weak evidence was considered wrong by most colleagues but later vindicated when strong evidence emerged”. (No mention of thousands of other dramatic hypotheses that turned out wrong.)
(2) “You may have heard in unsophisticated popularization that [philosophical claim ultimately hinging on semantic distinction] was false, but really it’s true [assuming my preferred semantics]”.
Aren't we all tired of this yet? Aren’t science journalists embarrassed by this stuff?
Firstly, the one who makes the logical fallacy inference that this implies all or most dramatic hypotheses are true is ... You. Not the author of the article. The author of the article is only talking about one specific theory. If I tell you a story about a chicken crossing the road, I'm not obligated to tell you about all the chickens who don't cross any roads.
Second, there are plenty of examples of established theories that started this way, and so it is important that scientists consider controversial hypotheses with an open mind. Speaking in any context, it's very easy to dismiss evidence that contradicts your views prematurely. It's sort of a defense mechanism we all do. It's important to recognize such a bias and be willing to acknowledge where your own theory could fall short when you see it.
My point isn’t that these can’t be interpreted correctly, it’s that these framings teach us nothing new because they have been repeated a thousand million times and this article does not attempt to go beyond the superficial cliche.
Hi!
for point 2#
I had many debates about this with Prof. that are cell biologists, and if you google "Are mitochondria alive," the answer Gemini will give you is no. This is very controversial in my academic circles, but I appreciate your thoughts!
Any time I read a mitochondria post like this, I strongly recommend that others who find the topic interesting check out Power, Sex, and Suicide by Nick Lane.
Absolutely loved TVQ. The insight about mitochondrial DNA inheritance being exclusively from the mother, thus motivating female fingerprinting of male nucleic DNA for gamete viability (via courtship rituals, pheromones, plumage, etc)...
>Defining mitochondria as “nonliving” isn’t just a classification mistake, nor a question of word choice. Rather, it is a fundamental misunderstanding of the nature and role of mitochondria. It inherently undermines our understanding of biological systems and deeply influences the tools we build to study them.
This assertion is made but not supported. I don't think I understand the importance of this distinction, assuming that everyone already agrees about the evolutionary and mechanical facts about mitochondria, but as far as I can tell, no one disagrees that mitochondria were originally free living cells, or that they have their own DNA, or any of the other relevant facts about their origins or how they work in the cell. It's merely an argument about what it means to be alive. Which is philosophically interesting, but practically unimportant for the practice of biology.
This seems like a purely semantic debate with no broader importance.
More than 95% of all proteins located in the mitochondrial compartments are encoded by the nuclear DNA, synthesized in cytoplasmic ribosomes and imported into mitochondria. These include factors that regulate mitochondrial DNA (mtDNA) gene expression such as mtDNA and RNA polymerases, mitochondrial transcription factors, RNA processing and modifying enzymes, transcription termination factors, mitochondrial ribosomal proteins, aminoacyl-tRNA synthetases, and translation factors (1, 2).
It's clear that a mitrochondrial element can't live for long without the presence of the host cells, so, like a virus, it doesn't meet all the requirements to be considered fully living.
> Defining mitochondria as “nonliving” isn’t just a classification mistake, nor a question of word choice. Rather, it is a fundamental misunderstanding of the nature and role of mitochondria. It inherently undermines our understanding of biological systems and deeply influences the tools we build to study them.
Once you accept mitochondria as alive, you might be motivated to explore its "potential" niche, as described by the author. The example of implanting cross-species mitochondria in human cells (e.g. from a gorilla) might lead to novel therapies.
It's about breaking outside the box of mitochondria having to live inside specific environments.
I recognize that you might be motivated to explore removing and implanting mitochondria regardless of whether you consider it to be alive (as you might think about implanting an organ from another source).
I think the main point the author is making is to not fall prey to reductive thinking about mitochondria's potential and less about the question of "aliveness". We were all taught about mitochondria producing ATP, but it sounds like it serves many other functions and there's a lot more to explore about its potential in synthetic biology and therapeutics.
So the theory is that if we don't accept them as alive, then we can't experiment with implanting cross-species mitochondria in human cells? Why not? What stops us from doing this?
This is a fair point. I can see the excitement around recognizing that mitochondria is alive to motivate exploring its other functions. But I think you're right someone might be interested in that exploration regardless of whether it's considered alive.
Edit: to your point, there are plenty of scientists interested in studying viruses and much debate about whether or not they are alive. Ultimately it probably doesn't matter.
I do think when you consider mitochondria to be alive, it broadens the scope of your thinking because you start considering each characteristic of life in relation to mitochondria. You might not be motivated to do that without thinking in those terms.
It doesn't seem the article addresses this, but I'd ask these questions: "would it be possible that mitochondria's evolutional interest and the organism's interest are not aligned?" "how many independent DNA can an organism possess?" "why mitochondria do not elicit immune reactions? Or can they?"
2) By "organism" I assume you mean "cell" since humans have several thousand different species with their own DNA living on or inside the body at any given moment. We can speak of animal cells, which have two (species and mitochondria) - and plant cells, which have three (species, mitochondria, and chloroplasts). If there can be one two or three, I don't see why there couldn't be even more.
3) Mitochondria are usually sequestered within the cell, which limits their exposure to immune cells. The immune system primarily targets pathogens that are outside the host cells. In fact, some pathogens can exploit mitochondrial pathways to evade immune detection - the most famous of which is HIV.
It matters for a number of reasons, but the main reason in terms of pure biology is that it was not originally recognized that cells could absorb other cells and utilize them for the absorbed cell's natural function.
This meant, importantly, that we learned cells did not always need to evolve a functionality from scratch, but could acquire it through phagocytosis.
It's also a useful tool for studying evolution for many reasons.
Whether or not mitochondria were once viable independent organisms that were absorbed by early eukaryotes does not depend on whether we call their modern descendants "living" or not. If we determine that they did, then we still don't have to call them alive -- certainly things like mitosomes exist and are suspected to have either evolved from mitochondria or evolved after amitochondrial division, but do not have DNA and do not reproduce independently but fulfil similar functions.
We know they have DNA, we know they reproduce independently of the host cell, we know to a degree why they tend to move to both sides on cell division. We know lots of stuff about them and we can always learn lots more. Whether they are "alive" or not has absolutely no bearing on that, other than to naval-gaze.
I think we're in agreement then -- this article is not about "did mitochondria evolve from absorbed viable organisms as opposed to evolving directly", which is an interesting question that impacts our understanding of evolution in microbiology. The article is about whether "Microchondria Are Alive" which is a useless naval-gaze.
For example I could easily see a scientist asking the question, "if mitochrondira are not alive, at which point did the phagocytosis of the initial prokaryotic cell lead to the mitochondria not being alive?" "What components were lost in the cell that lead to the loss of life?" I agree these aren't particularly useful, and are ultimately definitional, but definitions matter a lot in science, especially when paradigms change.
This is a much more interesting question, and this is what I mean by an operational definition of life. In your first question, "alive" can have useful operational definitions -- whether it is viable outside of a cell, whether it has or had its own immune system and structure, how it survived without the organelles that other full-fledged cells seem to have but mitochondria lack, etc.
The question in the abstract is not really useful except to answer trick questions in bar trivia.
I was equally dismissive of the actual importance of philosophizing whether mitochondrias are alive or not, but this paragraph made me change my mind.
> It seems Mitochondria are not bound to their host cell; they can travel between different cells. Although different species carry distinct mitochondria, experiments show that mitochondria from one species can be transferred to another.
> In 1997, scientists isolated mitochondria from chimpanzees and gorillas and showed that they are naturally internalized and integrated into human cells. Notably, the addition of external mitochondria even showed therapeutic benefits in heart failure and spinal cord injury. Thus, the potential niche that mitochondria can live in is greater than their effective niche.
So it seems like they are more symbiote than organelle, that's amazing.
The question itself if just semantics. But considering our mitochondria as evolving populations subject to selective pressure and genetic drift is really important to understanding their role in our health, down to basic questions like "Why is exercise healthy?"
That seems to be an overly reductive view on the value of knowledge.
What practical purpose does studying ancient civilizations have? Why do we send expensive telescopes into space to study faraway galaxies and try to uncover mysteries of the big bang? When can we expect the results from number theory to lower the price of gas at the pump?
Knowing that mitochondria have their own DNA is knowledge. Knowing that they reproduce independently of their home cell is knowledge. Learning whether they evolved from a separate viable organism would be knowledge. Learning whether we can make them viable, or breed them separately, and use them in therapies -- all knowledge.
Whether they are "alive" or not is just the definition of a word.
Much of science is about defining words in ways that match the underlying general structure of the system being studied.
A subset of scientists want to come up with an operational definition of "What is life", which may or may not include things like viruses and mitochondria. As you say, it's mostly definitional, but by defining this, we can potentially make our understanding match up with the latent reality.
Random thought after reading all the philosophical and semantics tangents in the comments here:
A good example of a memetic equivalent of endosymbiosis could be Christianity - Catholicism in particular. Historically, as Christianity spread around the world over the two millenia, it would often adapt and absorb indigenous beliefs and practices of converted populations[0]. Many would die out over time, but some got integrated into the core and exported globally.
It's just the right time of year to think about Christmas[1]. Can you imagine Christianity without one of its two core holidays? That makes it probably the closest memetic equivalent of a mitochondria - you can still see in it the distinct outline of an ancient Roman festival that was absorbed early on, but all of its memes live on in Christianity. In our times, the holiday is vital to the overall faith, and itself could not exist independently[2].
--
[0] - I've always been taught that this was intentional slack to make it easier for people to accept a new religion, but nowadays I feel it might have been a fundamentally unavoidable outcome. Maintaining organizational coherence and belief consistency at a scale of a whole continent requires communication and bureaucratic technologies that didn't exist until the last 100-200 years.
[1] - Or at least so most shops would have me believe; in western commercial calendar, Christmas starts when Halloween ends.
[2] - Well okay, I admit this might be a weak part of the analogy - in the western world, Christmas got commercialized to the point it could likely survive as an independent secular tradition.
> Historically, as Christianity spread around the world over the two millenia, it would often adapt and absorb indigenous beliefs and practices of converted populations
Certainly, in the Eastern Orthodox church it's commonly called "baptizing the culture". The idea was/is to take what is good from a culture and to incorporate it to help people become Christians. Also it's a core part of Christian missionaries to learn the language and translate the scripture, and if needed to create a written form of the language.
So I'd agree Christianity has always been a bit of a symbiosis of cultures, analogous as you said to endosymbiosis. It started purely Judaic, incorporated large parts of hellenism, and spread globally and imported more bits. The Jewish and Hellenic pieces aren't completely mixed, sort of similar to a mitochondria actually.
Then again it makes sense of a religion with a core belief that God became man and created a symbiosis of the two as their savior.
The fact that every child on the planet is religiously taught that the mitochondria is the powerhouse of the cell is all the evidence I need that we're upholding a primordial contractual agreement and these are the conditions to which we are beholden.
Name a single biological entity that has a better PR department. The only one that comes close is Athlete's Foot, which makes the victim sound cool.
I actually never heard the phrase until I got online and saw the meme!
My biology classes did have us gene editing bacteria to chance its color. That was fun!
> The only one that comes close is Athlete's Foot, which makes the victim sound cool.
The best cure for athletes foot is a 30 minute soak in diluted bleach. Get a wash basin, fill it with warm water, and add enough bleach so that it tingles a little bit.
Do this every other day 3 times, e.g. Monday, Wednesday, Friday. Problem solved.
Make sure to clean out the shoes as well, ideally not wearing any infected shoes for a few days at least, and soak the insides with Lysol a few times to prevent reinfection.
Depends on how diluted the bleach is. Also 30 minutes may be more than necessary, but it's what I've always done for athlete's foot. For other random crap that's tries to grow on my skin I'll dilute some bleach on a paper towel and let that sit on whatever is trying to eat me.
The basis of this technique is that you have skin to spare, and your skin regrows.
>"Name a single biological entity that has a better PR department. The only one that comes close is Athlete's Foot, which makes the victim sound cool."
The explanation doesn't get much better at higher levels. You have the Krebs cycle which biology people religiously memorize but it doesn't really explain much either. The actual interesting part is usually handwaved away as "magical enzyme/protein" catalysis. Understanding how the mitochondrial proteins/enzyme catalysts function would usually require a graduate degree, and maybe a background in biochemistry and biophysics.
If you haven't, I suggest you look up an on how ATP Synthase uses the proton gradient to create ATP. It's quite amazing. It's literally a little nano-machine.
As far as I’m aware we’ve never worshipped mitochondria. And unless you want to count eating which is technically true but not philosophically so, we don’t sacrifice plants or animals to mitochondria.
Nitpick: except red blood cells. White cells very much do have mitochondria.
RBC's don't need them because they are incredibly low-metabolism. It's energetically cheaper for the organism just to make them, let them go for a few months, and then recycle the components.
Key fact (left out of the article): most of the mitochondria's essential proteins, including those for ATP/energy synthesis, are produced by the host cell from the host cell's DNA. So yes, mitochondria have some DNA and do replicate, but no, their cell is not just an "environment" for them.
Also interesting: mitochondria can join (often to rescue one failing due to transcription errors) and be transported to other cells across bridges (to supercharge the recipient, as they want to do now for immune cell therapy).
It's such highly unlikely chance events that make me think we really are alone in the universe (we = a sentient civilizational lifeform). There's just no way the long series of extremely improbable events that led to our rise was replicated anywhere else, and it took the sheer vastness of this universe for it to have emerged even once.
Not even that. There could be better civilizations than us out there that either
1. Died off or regressed
2. Plateaued
3. Is sufficiently far away or stealthy enough for us not to notice them (whether intentionally or not)
I've often thought about the whole communications bubble argument... I don't buy it. I'd imagine, like wifi, other civilizations will maximize their communication bandwidth, which essentially also maximizes entropy which looks like noise to us. Compression, encryption, redundancy, multiplexing over frequency and amplitude and time, directional antennas and signalling... That's what we've done in under 100 years.
I know there's stuff like organic markers etc, but if machines are doing most of the heavy lifting I don't think that would matter. Same with stuff like hydrogen emissions lines. Whatever is abundant will be used for "settled" and "dead" solar systems alike.
This is a such common logical fallacy that we should have name for it.
> No matter how low the odds are, the counts of those potential interactions bring this outcome to a certainty.
"No matter how low", really? Are you suggesting that your multiplication result is infinite? Otherwise, no matter how big the result is—even if it's Graham's number or TREE(3)—but as long as it's finite, there are odds so low that bring the outcome extremely unlikely.
The thing is we don't know even a ballpark estimate of the odds, but you were saying like we have a lower bound of the odds. The universe is unfathomably huge, true, but we also don't know if abiogenesis is less unfathomably unlikely.
The issue here is that the interactions over X billion years are not the same. Each event that happened on this rock would also need to happen else where to have the same evolutionary pressures applied.
> No matter how low the odds are, the counts of those potential interactions bring this outcome to a certainty.
That is simply not true. Events are classified by probabilities, and there are a whole lot of things with a probability a lot less than will happen across the whole ocean across however many billion years.
All the higher-probability events will occur, yes. But a specific sequence of multiple extremely low-probability events? That then continues to replicate before it gets wiped out by chance?
Not a certainty, absolutely not. Contrary to what you say, it matters very much exactly how low the odds are.
this is the first ive heard of mitochondria replicating separately and distinctly from the host cell, how fascinating!
Are we saying that mitochondria have their own life cycle inside of a cell? living/dying/replicating in the span of the "life" of a single host cell? When a host cell reproduces, how does the mitochondria get produced in the new cell to get things started?
The two halves of the divided cells will usually both have mitochondria. Not always, though; sometimes cell division leaves one cell without any mitochrondria. That usually results in a non-viable cell, but sometimes the cell can survive with limited capacity. Some species that used to have mitochondria have apparently been through this process and have evolved to survive in their absence; Giardia duodenalis for example.
"If we think of mitochondria as non-living organelles..."
mitochondria were thought to just be a component of the cell. But they have their own DNA separate from that in the cell's nucleus. They replicate on their own like bacteria.
Organelles are alive too. All active biological systems are alive.
Mitochondria have for many generations now been known to have their own DNA and replicate on their own. So I’m not sure what new distinction is being drawn?
I _think_ what they mean is it's not typically listed as a "life form" in its own right, i.e., there's no Domain under which one would classify Mitochondria - maybe just calling them bacteria would capture the article's intent?
So, the modification would be that we are living in symbiosis with mitochondrial bacteria, similar to how we live in symbiosis with our gut bacteria, rather than them being classified as "organelles" of eukaryote cells.
As others note, it is classified in the tree of life. We know approximately what kind of bacteria it evolved from, and mitochondria themselves constitute their own divergent branch of the tree of life (there are many longitudinal studies of mitochondria across species).
But if you wanted classify them based on functionality rather than evolutionary history, I'd say they're more like viruses. They have only a handful of genes themselves, and exploits the nucleus' genetic material for all the other proteins it needs to function.
That's more a flaw of classification systems though. Because even if they comprise a distinct life form does not mean they need to have a unique species. Consider lichen, which comprise two (or more!) separate "species" which becomes a meaningless distinction when they cannot survive on their own, or even if they could, not in a form recognizable in any wayas they were when they were a part of the symbiotic system
I mean at that point what do we consider multicellular organisms? Did you see what was going on with those frog skin cells and "xenobots"? Also, our gut bacteria kinda makes us a symbiote at a larger scale.
Depends on your definition of organelle (whether you limit it to plastids/mitochondria, both of which were derived from external independent living cells, or use a more expansive definition that includes more cell compartments that weren't derived from independent living cells).
General acceptance of the endosymbiont theory is a relatively recent (much less than 50 years) phenomenon.
That's a discussion about word semantics that has no relation to biology. Biologists have been occupied with it for centuries, just like computer people have lost time on "what's intelligence?", but neither one is relevant for either field.
> Are they bacteria?
Once upon a time, their ancestors were. I do not know exactly where biologists trace the line, but this is also about word semantics. It's just a case of it that helps people communicate better, so there is a line, I just don't know what it is.
What do you mean by "alive?" Because of course they are alive, regardless of whether you consider them bacteria or not. There is a strange definition of "alive" that is being used by you and the author article that I'm not understanding.
If a mitochondria is not "alive," then is it dead? Even if it is taking part in an active, living cell?
I think the idea here is that mitochondria developed independent of cells and later lived exclusively inside of them. In other words, they reproduced without cells. I am not sure, please correct me if I am wrong.
You're not wrong. But over the enormous amount of time since, the "duplicate" organelles and systems needed for independent living were steadily carved out of mitochondria. While they do have their own DNA and replication process, the DNA is basically limited to specific things they need to perform their energy-generation functions and the replication happens when triggered by host cell replication.
It's a bit like if you took the heart from an animal and transplanted it into a human: is it meaningful to call it independently alive? Maybe, it depends what question you're trying to ask.
I don't know of any definition of "alive" that can survive application of a reductive understanding of biology that doesn't either count viruses as being "alive," or decide that nothing is alive.
The uncertainty, I understood, was whether to classify them as distinct organisms the way we classify other species, as they are intrinsically parasitic for their replicative capability.
Outside of a host cell viruses do not fit any of the definitions of life:
- they do not seek or consume sources of nutrients or energy
- they do not have a metabolism
- they do not grow
In fact the only place they fit the definition is reproduction, and that is only through the machinery they commandeer from the cells they infect.
To me viruses clearly do not fit the definition of life. But fire... that is hard to exclude from the definition without some mental contortions. I am not advocating that fire is alive for any useful reason, but it is hard to exclude from the definition.
I am terrible at biology but I will try. The idea is that mitochondria is not a component of a living organism, but an organism that once lived independently of the cell.
Here is an animation of the Mitochondria in action.
The mitochondria has two cell membranes. The gap in between is called the intermembrane space. It is also positively charged with protons. There are complexes 1-4 which continuously pump protons into this space. The ATP synthase molecule harnesses these protons, similar to a water wheel harnessing the flow of water, to make ATP which is the energy molecule the cell uses.
a lot of focus on the definition of "alive" in the comments, but i think that the weight of this rests on it being a step toward confirming the endosymbiotic relationship theory which states that mitochondria were potentially part of another eukaryotic cells carrying what would become mitogchodria were engulfed by another cell. this affected cellular development by outsourcing energy production for the cell itself. a lot of times the results seem "self-evident" but you still have to find evidence to support or reject a theory and this seems like a step in that direction.
I still think about the fact that we're this close to proving the protocell theory, proving that we can create life from no life. Last time I read about it was 2021, and I'm really curious when the day arises we succeed
They are obviously alive, but also we are obviously a colony organism. The various bacteria we transmit from mother to child, the mitochondria inherent to our cells, all of this stuff is just part of a self-similarity of life from top to bottom. With sufficient zoom-out, we need not treat individuals (or pairs) as the only unit of life replication.
This feels a lot like the debate about whether Pluto is a planet: what we're really trying to figure out here is whether we can figure out a definition for a concept that includes all the things we think should be included, and excludes all the things we think should be excluded -- and the meta conversation is: can we all agree on what should be included/excluded? That's a bit of a dance, since a cleaner and simpler definition can swing people's opinion about inclusion/exclusion, so the influence goes both ways.
Okay, what about the Earth? If mitochondria are alive, you must also consider the Earth as being alive too. Personally, I think it's a simple answer. Here's my positively b reasoning on the topic for anyone daring enough. It can be a very blurred line, but much of that is our shadow. Mitichondria are more alive than they are dead. Simply because they exist as potential and can go on and are intended for this, for lack of better words. Where as a rock will not come alive, no matter the conditions. We hope.
Maybe we should think of it like we do for other forms of energy and how I be thought we did think of it already but was of biochemical energy expressions. Along with kinetic energy, potential energy, chemical energy. Surely there is a number determined for the maximum lifetime energy output potential (work) of a single mitochondrion. While it is plain and simple, that's just life for you
Okay, what about the Earth? If mitochondria are alive, you must also consider the Earth as being alive too. Personally, I think it's a simple answer. Here's my reasoning on the topic for anyone daring enough. It can be a very blurred line, but much of that is our shadow. Mitichondria are more alive than they are dead. Simply because they exist as potential and can go on and are intended for this, for lack of better words. Where as a rock will not come alive, no matter the conditions. We hope.
Maybe we should think of it like we do for other forms of energy and how I be thought we did think of it already as biochemical energy expressions. Along with kinetic energy, potential energy, chemical energy. Surely there is a number determined for the maximum lifetime energy output potential (work) of a single mitochondrion. While it is plain and simple, that's just life for you.
"Molecular biologists tend to focus on characteristics like metabolism, growth and development, response to stimuli, reproduction, and the ability to process information or evolve."
Even if you stretch the others real hard, I don't see how you'd argue that the Earth "reproduces." Especially not the more rigorous definition of reproduces fertile copies of itself which can evolve.
> If we think of mitochondria as non-living organelles, how will we ever harness their full potential?
"Alive" is a fuzzy boundary in concept space that helps humans navigate a fractally complex world. It's not a fact about mitochondria that either hides or reveals structure. We can harness the potential of viruses, and reasonable people can disagree on whether they are alive.
> If one considers bacteria as living entities — and all biologists seem to — then it is impossible to explain why mitochondria are not.
There seems to be a strange, half-hubris, half-pride vein that runs through Humanity that would see us as lesser for being hosts to benevolent bacteria, despite us very obviously being unable to survive without benevolent bacteria.
We didn't evolve to understand "self", and indeed most animals do not. There was no evolutionary pressure to do so. We're having to discover it piece by piece.
We aren't driven solely by evolutionary pressure. We can (and have) developed cultures that can easily accept that humans are "just" part of a larger system, even having a unique role, without having to be superior. Our culture isn't like that, of course. We are obviously doing a good job of being "in charge" of the planet and definitely not charging headfirst into a mass extinction event with our collective eyes closed.
Wonerful! This article is a mind-meld of Humberto Maturana’s work on autopoiesis with almost any of Nick Lane’s deep discussions of bioenergetics e.g., the wonderful book “ Power, Sex and Suicide: Mitochonria and the Meaning of Life” or his equally strong book “Transformer: The Deep Chemistry of Life and Death” that is focused on the Kreb’s cycle. He brings biochemistry and bioenergetics alive in a way that will impact your thinking.
Maturana and Valera gave a brilliant definition of “living” in Autopoiesis and Cognition: The Realization of the Living” (1980). But their writing style will make this a tough read. Terry Winograd write a useful summary if Maturana’s philosophy in his computer science classic “Computers and Cognition”.
> My heart can exist independently of me, and be transplanted into other people, but does it mean that it is alive?
Interesting analogy, made more interesting still if one replaces "heart" with "brain."
And what if you reverse mitochondria and host cell? If you remove the mitochondria, is the host cell still alive? The analogy would be to remove the heart from its 'host' environment, and asking if the remaining body still can be called alive.
"for a man cut open is, so far, not a man. And if you do not sew him up speedily you will not see organs, but death."
Today I learned that mitochondria are the only organelles that replicate “on their own” inside a cell, while the other organelles just bud off the preexisting ones. I wonder how they are signaled to do so though.
Reminds me of sea slugs that eat plants and then integrate their chloroplasts to produce energy, or my dad who kept swapping the same Honda motor through all our go karts because it was too good to get rid of.
If you want a fun scifi horror novel to read related to this topic, check out Parasite Eve by Hideaki Sena. It's the novel that inspired the PSX game. The whole plot revolves around mitochondria and was inspired by the author's time as a grad student. I read it a few months ago and really enjoyed it.
Consider that there are thousands of mitochondria (MT) in an individual muscle cell. Cell diagrams often make it look like there is one MT organelle. It's highly misleading.
Single cell bacteria have thousands of genes. MT have a few dozen genes. Many of the genes that regulate MT are contained in the cell's nucleus.
As a layman I'm kind of baffled by the enduring pop-sci interest in mitochondria.
To me the far more interesting organelle is the ribosome. This elegant self-replicating machine that is highly conserved across lifeforms is fascinating and much closer to the origin of life than mitochondria.
How did ribosomes evolve? Are the ribosomes that we see in modern organisms the first design that did evolve? Why are they highly conserved?
That's a debatable statement and it doesn't explain the public appeal of mitochondria over ribosomes that predates recent research on the relationship between mitochondria and aging.
But there is a connection between the X and Y in this case.
One is a subset of the other. We're talking about the same thing man, I'm just making the point that I feel that there should be greater emphasis on the subset.
Look at the top thread in this post, people are doing a very similar thing.
I truly think that the pop-sci interest in mitochondria stems from the nickname and for no other reason and to me that's a very interesting thing.
It's a little confusing to look into, because there's a bunch of separate theories about the nature of aging that all involve mitochondria in some way. You will find news articles saying that the mitochondrial theory of aging was discredited because of some study done, but when you look into it, it turns out that what was shown was that some specific variant of the theory was insufficient for accounting for all forms of aging, which is not the same thing. Each mitochondrial theory of aging is a theory about one pathway by which mitochondrial function or dysfunction results in aging damage, the reality is that many or all of these theories are true and aging is the aggregation of damage from all of them, and more pathways we have yet to discover.
Generally speaking, the vast majority of aging damage comes, directly or indirectly, from the accumulating damage from healthy operation of mitochondria over long periods of time, or the accumulation of cells with unhealthy mitochondria that produce damage more rapidly. The ELI5 is that mitochondria produce free radicals, free radicals chemically alter basically anything they touch, and aging is simply the slow accumulation of intercellular and intracellular damage, and if you follow the history of these molecules back to when they diverged from being in a healthy state, it is almost always the result of oxidative damage (e.g. free radicals of the sort produced by mitochondria).
Another ELI5 way of looking at it: you may not know this, but mitochondria only live a couple of days. They are constantly being refreshed in your cells because of the severe oxidative stress they undergo. They also sometimes break or leak, letting those reactive oxygen species into the cell and causing damage. Aging is the accumulation of this damage.
But I said aging was "downstream of" mitochondrial dysfunction. That's because not all aspects of aging is due to reactive oxygen species leaking out like I seemed to claim above. That's just one example. There are cells in your body that have lost all mitochondria, often due to a freak genetic mutation in the mitochondrial DNA of that cell. Surprisingly these cells don't die, but rather switch into a mode of operation where they slow down and live off energy extracted from the intercellular medium and converted into ATP by various molecular systems embedded in the cell membrane. These processes, as it turns out, free radicals out of the cell during operation, spewing reactive species into the body. This ends up being responsible for hardening tissue, lack of energy, and many other symptoms of aging. But the root cause? The mitochondria stopped working in that cell, so still a mitochondrial issue.
Or, the aging of heart cells and the hardening of arteries is largely due to the collection of dysfunctional lysosomes that are full of garbage they are unable to break down. These clutter cells, harm their efficiency, and eventually have enough collective effect as to make the tissue as a whole less viable. Leading to heart attacks and other cardiovascular disease, which is the leading cause of age-related death alongside cancer. Want to guess what these defective lysosomes are full of? Mostly undigested mitochondria, specifically the highly damaged structures of mitochondria that suffered too much oxidative damage from long operation.
Oh, and what about cancer? Well cancer needs A LOT of energy to keep replicating, and so it should be no surprise that many of the mutations among common cancers have to do with genes in the nucleus affecting mitochondrial function, or the various signaling pathways between the nucleus and the mitochondria of the cell. This article covers some of the ways that cancer uses mitochondria: https://pmc.ncbi.nlm.nih.gov/articles/PMC4371788/
The best lay introduction I know is "Ending Aging" by Aubrey de Grey and Michael Rae. The book is meant to be an enumeration of all the things that need to be done to biologically reverse aging, but ends up being more than 80% about mitochondria and mitochondrial dysfunction, because of its out-of-proportion impact on the aging process.
Nah [1]. They do single task. They just read RNA, pick amino acids [1] and make proteins. If a cell were your house, it's like a 3D printer.
Mitochondria are much bigger, they have their own DNA, they reproduce, have a lot of internal structure, they do all the task of a normal cell. If a cell were your house, it's like having a bunch of squirrels trained to wind the clocks in exchange for peanuts.
[1] The definition of alive is complicated, so I prefer a "Nah" instead of a super hard "No".
[2] There are some details I'm hiding, like mRNA, tRNA and even rRNA.
I'd been taught mitochondria maybe came from bacteria back in high school 40 years ago but I didn't realise till now that Lynn Margulis also proposed the cell nucleus arose in a similar way.
I agree completely with all the points made in the article and would double down on the critique of the philosophy of biology as a discipline and science itself: namely that is has historically evolved as a mere system of typologies and that this is so settled in and so sacrosanct that biology is such a superstition with human-made categories a couple hundred years ago and not a real science.
We see the exact same things also when discussing what is a species and also completely disregarding the reality of horizontal gene transfers etc in the strict, traditional trees.
The models are quite wrong and even reduced wrong.
There is this one famous article that shows how traditional biology would go and analyze a transistor radio, namely just label its assumed components!
I thought the Mitochondria Liberation Front was defunct. Are people getting back into this type of linguistic debate? Anyway, uplifting as a whole is pretty sketchy and I'm not sure there's too much point.
Most of the Japanese games/media foreshadow/hint you about actual or potential facts written in papers but not understandable to teenagers until theẏ grow up.
I don't know why this is being downvoted. It's quite apropos for being a piece of fiction toying with this very concept.
It is a videogame based on/continuing a cheesy scifi novel that played with the concept of mitochondria being alive (also sentient). Sure it's not quite scientifically sound, but it still explains the concept with enough actual facts (very easy to distinguish from the fictional ones), and the ludicrous nature of it all makes it so you won't *ever* forget that mitochondria are in fact a part of the cell and their normal function is being involved in energy production.
I can warrant 90% of people who ever thought about the mitochondrion's existence and function (beyond basic school formation) that aren't working or studying in related fields are just people who played this game. I can bet there's a non-zero amount of scientists that got into this stuff because they played the game as kids or teens.
Surely I can't be the only one who read this as midichlorians and thought it was something to do with star wars. Actually feel a little ashamed about that.
Talking about what is considered "alive" is an interesting exercise, and shows just how fuzzy those boundaries can be sometimes. But I really don't see how this has any practical impact on how we study mitochondria.
> If we think of mitochondria as non-living organelles, how will we ever harness their full potential?
Whenever anyone uses the "harnessing [its] full potential" cliché, my bullshit alarm starts buzzing. I don't think this article is bullshit, but...we can "harness" as much "potential" as mitochondria have whether we consider them alive or not.
It's funny that this phrase has had such staying strength, while the key word in it, "powerhouse," has fallen out of fashion. The more modern American English way to phrase it would be "the power plant of the cell."
Anecdotally, I feel like I've heard "powerhouse" used somewhat regularly when describing impressive people, i.e.: "Such-and-such is an absolute powerhouse on the field", or "That person is so productive, they're a powerhouse".
So maybe the original usage has been subsumed by "power plant", but I think the word has alternative meanings which persist.
Powerhouse is a common way to describe an athlete, a high performance engine, or a very strong stock buy -- it has just moved away from the infrastructural uses.
That's an interesting thought, I haven't picked up on it but you're right. Most of my associations with powerhouse are from trails or ares that used to have powerhouses and now have empty buildings, ruins or traces left over. I do think about powerhouses in the context of dams but that is likely leftover from an earlier time.
Distinction: I am a millennial, and actually had to go look up just now what a "powerhouse" is. I am familiar with the term in its metaphorical sense, but was heretofore unacquainted with the literal definition. "Power plant" or "power station" would, yes, be more immediately understood by my generation. The phrase "Mitochondria is the powerhouse of the cell" would read to modern children like saying "The mitochondrion is the rock star of the cell."
These things do happen. I was in my 30s before I learned what the "firewall" of a car was...
I wonder what mitochondria dream about. Do they have elections? Politics? Their own understanding of the universe, that somehow ends on the skin surface?
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This article is framed as if there is something novel and profound here, but the "aliveness" of mitochondria is simply a matter of how we choose to apply the label "life" - a human linguistic construct that exists independently of the biological phenomena. This is not a new discussion - science has been considering this question for many decades, just as it has with viruses. These all come down to arguments about semantics and don't add anything to the science.
Mitochondria are fascinating and there is still a huge amount to learn about them but they are totally dependent on the cell's machinery. Most of their genes, the code for their structure, are in the nuclear DNA. A glaring omission if you are trying to make the case that mitochondria are independently living. My heart can exist independently of me, and be transplanted into other people, but does it mean that it is alive?
The implication of the whole article is that there something we have missed. This really isn't the case. Lynn Margulis's endosymbiotic origin of mitochondria was challenged by many, and it did spark a scientific debate - that's how science works. She won the argument comprehensively decades ago and is well established science. There have been many such endosymbiotic events in the history of life - there are subfields of evolutionary biology that study these processes.
> These all come down to arguments about semantics and don't add anything to the science.
This accurately describes much of science...
> My heart can exist independently of me, and be transplanted into other people, but does it mean that it is alive?
The cells that comprise your heart are very much alive, but they will die without support infrastructure. They live, they replicate, they die -- like every cell in your body. If I relocate you to the moon without support infrastructure, you would die too -- and yet (I think?) you are probably alive.
> This accurately describes much of science...
It is more related to the philosophy of science.
https://en.wikipedia.org/wiki/Philosophy_of_science
More like:
https://en.wikipedia.org/wiki/Ship_of_Theseus
Built with his grandfathers axe.
P.S. I'm not implying his grandfather was Gimli even if Gimli theoretically had two grandfathers.
One might say "natural philosophy"
Natural philosophy is what science was called before it was called science.
The philosophy of science is something that has only existed since the practice of science became widespread.
"Very much alive," in the sense of being a living organism in their own right. By that standard, each cell in the human body can also be considered a separate living organism, simply cooperating with other humans cells in a complex way. It makes sense, since we have no problem identifying the trillions of bacteria cells living on or in the human body as separate living organisms.
"Sperm and egg cells, known as gametes, fuse during fertilization to create a zygote. "
Since all humans were just 2 cells at one point. It seems to follow that the entirely of the code for what a human is, is contained in just those 2 cells. Not just code for a finger. But even code for our deeply ingrained fear of snakes. Was just at one point contained in those 2 cells. Kind of blows your mind.
If they are separate living organisms, then there seems something recursive about humans if they can be just 2 cells at one point.
I know this is not exactly your point, but it's important to remember that it's not exactly everything. The intra-uterine environment has a serious contribution to your development, and almost certainly transplanting the fecundated cell into a different mother would lead to a different person being born. Especially when it comes to things like intestinal flora, which mostly seems to get "seeded" from the mother during birth. Even the milk you ingest after birth significantly influences certain aspects of your basic biology (mostly the immune system).
No. The expression of genes is controlled by their environment. We are products of both nature and nurture.
If something dies surely it was alive once?
The final categorization is the least interesting part though. If we understand the origins and mechanics of how the once parasitic organism became an integral part of almost all complex life, does arguing the semantics of what label you put on it really add much value?
To reframe it: what you’re really doing is arguing about the definition of alive. In this case my opinion is: who cares. I fail to see how expanding the definition or being precise here adds anything.
> does arguing the semantics of what label you put on it really add much value
Refining the definition of something often helps provoke new understanding and tests of the limit of that refinement. It seems like a critical requirement in the "form a hypothesis" step of the scientific method.
i might be wrong but corporations/institutions never sponsor R&D in all directions so framing/phrasing is vital. but, from a philosophical pov, I agree with you.
> If I relocate you to the moon without support infrastructure, you would die too -- and yet (I think?) you are probably alive.
It seems to me that the alternative to people being alive quite quickly reduces to nothing is alive by way of information theory.
Life is not binary.
Best argument I've heard for Gaia theory, intentionally or not.
We probably can keep a heart alive outside of body, through artificial means, for minutes, maybe hours - and I mean keep it functioning, not just chilling it to slow its death. It's plausible we'll learn to be able to keep it alive for days, months, years, decades. At which point we could say that the "supporting infrastructure" of the rest of a human body isn't necessary for the heart to be independently alive?
What if we do it all on the Moon, or Mars? How does Gaia feel about it? We already know that it's theoretically possible, if not yet achievable in practice, to create artificial environments capable of supporting human life indefinitely - or, on a long enough timescale, bootstrap an independent, self-sufficient biosphere. The two are, in the limit, the same thing anyway.
Or are we going to argue that human technology is, by extension through causality, a part of life on Earth, and therefore a part of Gaia itself? Is Gaia in all of us, and will it persist after Earth dies if humanity is still around somewhere else?
All in all, I suppose the correct definitions of terms are the ones that are most useful in a given context :). "Categories were made for man, not man for the categories", and all that.
I’m not sure what you are arguing against. For me, the article offered a lovely reminder that life is special. Life involves mechanisms but it is more than a machine. And with an attitude that our lives our symbiotically bound to another living organism (or 10^17 of them) we gain a valuable humility — one that might afford us new perspectives on how to make them all happy and flourish. That’s the promise— not just a spiritual connection to the aliveness of mitochondria, but a pragmatic orientation towards their health and wellbeing. And there is a lot of scientific opportunity to explore there.
As I said in another comment, I think that mitochondria are fascinating, understudied and a rich area for research.
We are bound to the myriad other pieces of DNA that all have different evolutionary histories within us, we are symbiotically bound to many strands of life on many levels. We are just one strand, a part of a singular whole, bound to all strands of life beyond us. This view of life led me to science. I totally think that this view of biology is not properly appreciated by most scientists.
But this article was presented as a scientific piece and made the explicit claim that mitochondria were alive which is a semantic argument that doesn't have a scientific answer.
It is a well written piece that made it to the top of hacker news and it's great to see the debate.
But it just isn't true that mitochondria are alive by our currently accepted definition of alive. This is an old debate in biology that was settled years ago. There is nothing in this paper that wasn't known to mainstream science decades ago, but it is presented as a novel scientific viewpoint.
> it just isn't true that mitochondria are alive by our currently accepted definition of alive. This is an old debate in biology that was settled years ago.
Sorry, but that’s an overreach. There are many “accepted” definitions” of life across different scientific fields. According to Wikipedia, there are at least 123 definitions of life — and there is not scientific consensus. Mitochondria are alive based on some definitions and not alive based on others.
https://en.wikipedia.org/wiki/Life
Expecting life to have total autonomy in self-sustainability is absurd. Otherwise somatic cells or even people would be not alive.
And the argument that mitochondria are not alive because they can’t encode all their own proteins — well, I’ll point out that humans can’t produce all amino acids, either. As a thought experiment, if humans couldn’t produce a certain essential protein — and had to rely on a symbiont, would that mean humans weren’t alive?
Finally I’ll point out that Mitochondria can be healthy or flourishing — and they can be sick and die. How can something that is not alive, die?
It’s ok to argue for a narrow definition. But please don’t present this argument as though you are the defender of clear scientific conclusions. There simply isn’t consensus on this across the sciences.
I agree I didn't phrase that right. It was a short cut.
There has been debate over whether mitochondria can be called alive since at least 1890. For many years the vast majority of mitochondrial biologists have avoided the binary alive/not alive classification because there is a spectrum of 'livingness' and we can draw the line anywhere we like.
Picking a different line position is not scientific, it is semantics. What do we mean by the term 'alive'?
The article presented a profound new way of viewing the living state of mitochondria that was going to transform the world. It said nothing new, and failed to make any reference to the long term debate.
But it was a nicely written interesting article and mitochondria are going to be hugely important therapeutic area in the future.
I think they are arguing against the subtitle of the article: "Recognizing that mitochondria are alive will open new horizons into how we learn about, and build with, biology." Which seems a stretch based on semantics.
> The implication of the whole article is that there something we have missed.
I think this article is talking to people who haven't internalized the details of the scientific consensus. Those people are still going around, talking about "life" and making decisions based on the flawed understanding this article is critiquing. I think it's likely that the thing that "has been missed" is not narrowly scientific in the way you seem to be thinking - but more about broad implications and worldview.
I am not sure what exactly the 'broad implications and worldview' are here that are being challenged. The article is presented as a scientific opinion and references scientific research and has a doi number for citation (Cite: Liyam Chitayat. “Mitochondria Are Alive” Asimov Press (2024). DOI: https://doi.org/10.62211/38pe-75hu). What do you think that the article was challenging?
Obviously the article is challenging the view — scientific or not — that mitochondria are not living.
Side note: previously I was funded by NSF and NASA to study such questions from biophysics and astrobiology.
That said, this was a delightful read. I did not realize or conceive of mitochondria as, like bacteria in our bodies, independent living networks with unique genomes, evolution, and flows of information and energy.
Reading about the health benefits of “external mitochondria” made me think about when I hug my dog: are we exchanging mitochondria, perhaps?
Life is just an arbitrary number of magnitude of complexity
> Most of their genes, the code for their structure, are in the nuclear DNA.
Are they? I was under the impression that mitochondria are closer to pseudo-cells living inside human cells.
Wikipedia seems to confirm this [1]:
> Although most of a eukaryotic cell's DNA is contained in the cell nucleus, the mitochondrion has its own genome ("mitogenome") that is substantially similar to bacterial genomes.
[1] https://en.wikipedia.org/wiki/Mitochondrion
There's a specific page on Wikipedia about Mitochondrial DNA [1], where it is clearly said that:
[1] https://en.wikipedia.org/wiki/Mitochondrial_DNA[2] https://doi.org/10.1016%2Fj.cels.2016.01.013
They were, originally. Over the eons, they have lost many of their original genes. Source: Nick Lanes fantastic books, specially Power, Sex, Suicide
Saw another recommendation for that book in this discussion and will be reading it. Thanks.
See below on Wikipedia: "Most proteins necessary for mitochondrial function are encoded by genes in the cell nucleus and the corresponding proteins are imported into the mitochondrion. The exact number of genes encoded by the nucleus and the mitochondrial genome differs between species."
yes, Human mitochondria only generate less than 20 types of protein; all other things they need are from cytoplasm.
Yea I would def. not call mitochondria "alive" since they are so deeply integrated with the rest of the cell & vice versa.
mito is like <100k bp vs 3000000k bp in human genome (bp = base pair = "character" in a string)
principle derives from the concept of "the selfish gene" or "the red queen" these famous books on the topic. Arms races between X and Y chromosome. Arms race between nucleus and mitochondria, and so on.
or put it this way. why do all animals have sex? because it generates gene sequences that confer fitness more efficiently than self-replication (which is the typical repro method of unix programmers)... .. generates such gene sequences for NUCLEAR DNA that is, mito DNA comes from mom only (the red queen.. .. "mitochondrial eve" ... "y chromosomal adam".. etc). and thus the mito is fundamentally unable to wield the power of evolution, completely evolutionarily outclassed by those nuclear chromosomes. thus exporting all its genes to the nucleus, conferring advantage to all such progeny with their superior power supply
I don't understand this definition of "alive". Isn't every cell in my body alive? There are definitely differences between an alive cell and a dead one.
> There are definitely differences between an alive cell and a dead one.
Energy flow is the difference. but then everything has an energy flow. Losing and gaining electrons. So it is possible that literally everything is alive, don’t you think? Maybe the problem is is that we’re trying to make a definition where none ultimately really exists.
OP above you is correct. Maybe you are thinking about it wrong?
what about obligate intracellular parasites like mycoplasma? They are awfully close to mitochondria but we think of them as alive. They've lost many of their genes and can't survive without the host. Looking at those, you could almost see a path from an obligate intraceullular parasite to an organelle derived from a phagocytosed prokaryote.
But that’s exactly what they are, former endoparasites which gradually lost their independence and became more specialist in their function.
Defining an arbitrary line and then attaching labels does not really add to understanding.
But it does. How many grains of send form a heap? How many atoms form a fluid? Is it something a particle or a wave? The line can be drawn depending on specific problem, on how useful a heap/fluid/particle/wave model for this specific application.
A label (abstraction) allows us to bring corresponding tools that were developed for it. If you can count trees then the same math can be useful to count people.
Arguing about where you draw the line doesn't advance anything, it just muddies the water. We have robust definition of what is and isn't alive built by consensus. Mitochondria fall into the 'not alive' category by our definition. Presenting decades old scientific views as evidence that this categorisation is wrong doesn't add anything. This article has had far more exposure than some really groundbreaking science and it adds nothing.
This called symbiosis. When a parasite such as a virus, a bacteria, a fungus, a plant, an insect and its host find a win-win "agreement".
This "aliveness" debate reminds me of the "11.000 years old dog". Basically a tumour that has been spreading from one dog to another for thousands of years.
https://www.cam.ac.uk/research/news/11000-year-old-living-do...
> My heart can exist independently of me, and be transplanted into other people, but does it mean that it is alive?
Your heart cannot exist independently of you as a heart. It is only a heart in name, as it does not function as a heart. Its identity as a heart depends on its ability to function as a heart within some organism. The same can be said for any part or organ. A severed hand is a hand in name only. A corpse is not a body, as it no longer functions as one.
A transplanted heart becomes a heart once more. A reattached hand becomes a hand once more. If you think this is weird, then you haven't done your metaphysical homework. Why should it be weird? It could only be weird if you have made certain (unexamined) metaphysical presuppositions. The structure of a heart removed from an organism persists long enough that it can become reintegrated into an organism such that it functions once again as a heart.
But also note that the matter composing a heart itself isn't fixed. About 1% of heart cells are replaced per year in the young. So if function and structure can survive transient material change, and the matter that makes up a heart can assume and lose and reassume its identity as part of a heart, then why can't a heart lose its identity as a heart when removed, and regain its after it is implanted back in?
Mitochondria are weird. Look at 3-parent baby (human).
You might find this interesting:
"Clinical potential of sensory neurites in the heart and their role in decision-making"
[] https://pmc.ncbi.nlm.nih.gov/articles/PMC10896837/
> There have been many such endosymbiotic events in the history of life - there are subfields of evolutionary biology that study these processes.
Exactly, if mitochondria is alive then so is chloroplasts and who knows what else. The line needs to be drawn somewhere, also life and death isn't as clear-cut as many used to believe
I think questions like this make science fun for the uninitiated because it represents both the uncertainty and the intense investigation and evidence discovery process involved in tearing hazy things and recovering concrete truths in the process
Are you not "totally dependent" on the air you breathe, the water you drink, the sunlight that gets turned into your food, ...?
It's wild to me that today's popular biologists like Michael Levin don't give Lynn Margulis credit in every single podcast/interview.
Can you elaborate on this comment? What should popular biologists like Michael Levin be saying on every podcast/interview and why? Serious question from someone who is familiar with Lynn Margulis but not Michael Levin.
I don’t disagree with your take. The concept of the semantics of “what is alive?” has been going on for a long while now.
Have you considered that this is a more formal version of a Bill Nye science explainer, but for adults?
The reason I say this is that while unintended (I think) your post has a, “of course they’re alive, we’ve known this forever” vibe, which can inadvertently come across as condescending.
I don’t mean to pick on you, we’re all guilty of such speak when we deem concepts to be obvious or well known.
Your post reminds me of the “1 in 10,000” XKCD comic:
https://xkcd.com/1053/
Again, I don’t disagree that your knowledge of history and science is correct. Am just curious why you wrote your explainer in the way you did.
Hi!
I agree with you, which is why I wrote this- but if you google "are mitochondria alive" gemini says it isn't. And yes, the cells in your heart have an effective and potenitial niche!
We seem to have many tools to engineer viruses, but few to engineer mitochondria- perhaps considering them as alive could change that!
I am not sure you should be relying on an LLM as any indication of anything...
More seriously, considering something as being alive in order to engineer them better does not necessarily change the fact of them actually being alive or not, in my opinion.
If LLMs work the way I understand them to, they are trained on large corpora which contain a statistical preponderance of statements which are consistent with the current scientific mainstream, so it may not be completely crazy to try doing this; you'd get the scientific mainstream explanation, and possibly a few alternative hypotheses if they had enough literature support.
Why would it be consistent with the scientific mainstream? Unless there's evidence that scientific reports and material are specifically up-weighted during training and prioritised somehow, whatever an LLM says will be only consistent with its training material, which could have any proportion of fake articles, Reddit posts, Quora responses, encyclopedia pages and joke blogs
> which are consistent with the current scientific mainstream
This seems to require a high amount of curation of training inputs, but I haven't done real digging into it, just going off the more casual "all of stackoverflow" or "all of reddit" type comments frequently thrown around. But if there is such a curation I'd agree, I just don't think there is that curation.
You don't know what the training data is and what each category's weights are, so how can you assume that?
Most use common crawl, and most seem to upweight the scientific publication part of it (from what I gather speaking to folks who train LLM models).
You are literally saying this novel thing is wrong because this thing that can't say novel things says the thing that's not novel is not novel.
> if you google "are mitochondria alive" gemini says it isn't
And my grandmother is a bicycle.
Therefore, a man needs God like a fish needs your grandmother!
Still one of my favorite idioms
I just tried that and it said:
>Yes, mitochondria are alive, though they are not considered "living" in the same way as a cell because they can't function independently...
Maybe it's learning!
Or maybe the temperature is set too high! Probably don't start with a single LLM response as the basis for your understanding of scientific consensus.
Eukaryotes generally can’t survive without mitochondria either. It seems silly to discuss if different subsystems in a living organism are independently “alive.” It’s a bit like arguing if just the wings or just the engine of an airplane are flying machines.
You are completely right that we should be thinking far more creatively about manipulating mitochondria. There are a lot of diseases (including Covid) that have mitochondrial aspects. I just don't think calling them alive helps, other than to get you some decent exposure on HN :)
"Gemini" says? So what?
It shows there are misconceptions out there, if only in LLMs.
Mitochondria are why I’m a Rare Earther.
In Earth’s history, mitochondrial endosymbiosis occurred once. Without that you don’t have the energy budget for complex life. Moreover, there may be a narrow window where it can happen: modern microbiology has defences and selection pressures that it make inhospitable to the hobbling chimeræ the first mitochondrial cells would have been.
Until mitochondria, the emergence of life from nothing is plausible. With mitochondria, its progression to complex, multicellular and intelligent life makes sense. Both processes in small steps can be replicated, more or less, in the lab. But that one moment is not and has not been. As a result, I think the universe has lots of living slop but very few plants and animals.
(Aside, look at ATP go: https://www.youtube.com/watch?v=lUrEewYLIQg&t=939s)
This process, known as primary endosymbiosis, happened at least twice, for mitochondria and chloroplasts. Further, while all chloroplasts (and more widely plastids) appear to share a common ancestor, there is evidence that mitochondria may descend from multiple lineages that underwent lateral gene transfer and/or convergent evolution. Nitroplasts are a likely another, separate instance of primary endosymbiosis.
There is also secondary endosymbiosis, where the endosymbiont organelles of one eukaryote are engulfed and incorporated into another eukaryotic cell to create a new type of endosymbiont. This has happened at least 8 times.
There are also theories that some other organelles are the product of other endosymbiosis events, many of which also have some of the hallmarks like their own genetic material. These theories are more speculative though.
It's also worth noting that while eukaryotes obviously gained some important capabilities from incorporating these endosymbionts, the endosymbionts they incorporated obviously managed to just evolve to perform those functions directly. Further, while one of eukaryotes' distinguishing features are mitochondria, there are several other major differences, and mitochondria are not believed to be what made eukaryotes better able to evolve complex multicellularity. Prokaryotes have indeed evolved multicellularity dozens of times, and we arbitrarily set our definition of complex multicellularity to distinguish from what prokaryotes have achieved.
The first time it happened involved a huge number of changes in the host cell, like the creation of a nucleus. That makes it seem more likely that an already eukaryotic cell can more easily incorporate other endosymbiotes.
Observation of prokaryote/prokaryote endosymbiosis would be real evidence against the rise of eukaryotes being the or one of the main limitations in the number of intelligent species in our galaxy.
There's really only one change that mattered - phagocytosis. The ancestor of all was a prokaryote that practiced phagocytosis, the process of engulfing other cells. Endosymbiosis resulted from some of these engulfed cells not being digested.
There are no known modern prokaryotes capable of phagocytosis. Presumably the extinct prokaryotes who were capable, including those from the same lineage as the eukaryotes but which did not pick up mitochondria, were outcompeted by the eukaryotes who occupied the same niche.
Other changes like the origin of the cell nucleus and many other organelles can be readily explained by other malfunctionings of the phagocytosis process. Basically once you have the ability to pinch off parts of your cell wall into internal structures, you suddenly get a bunch of internal structures made of stuff that look surprisingly like cell wall.
I believe there was an article here suggesting rather enthusiastically that nitroplasts are endosymbiots. Sometime in the Spring I believe.
See also: nitroplasts
In addition to what others have pointed out (chloroplasts), I think this makes another mistake. Although only the mitochondria and chloroplast lineages remain, it is possible it happened other times but those lineages were out-competed, for whatever reasons, and are now extinct.
> it is possible it happened other times but those lineages were out-competed, for whatever reasons, and are now extinct
Chlorophyll probably outcompeted retinal [1]. (The stuff in our eyes.)
The reduced form of my claim is that mitochondrial life so freakishly outcompetes its competitors as to be in a class of its own. Which still yields a rare Earth, albeit a first among many.
[1] https://en.wikipedia.org/wiki/Purple_Earth_hypothesis
In an evolutionary process, one lineage running away is the most likely outcome. It's very unlikely that two competing lineages would evolve to be exactly equal at the same time and remain equal for an extended period of time.
> In an evolutionary process, one lineage running away is the most likely outcome
What are you basing this on?
It's based on the fact that one explanation of why there's not even millions more species of all life, is because the more successful ones simply cannibalized the less successful ones. This would've started even before complex life, almost at the chemical level.
I say cannibalized, because avoiding eating your own species is a higher brain function that would've came far later, so it came down to eat or be eaten. Still is frankly.
Species (maybe only [di?]morphic ones) rarely kill other instances of their own species, only maim - usually to the point of socially/reproductive shame/selective behavior; as infra-species violence is usually done for sexual signaling.
Like squirrels neutering each other, giraffes ruffling neck-fights, etc, it is not generally advantageous to actually hurt the opponent more than needed to signal dominance in a social hierarchy - this "gentleman" agreement is similar to all emergent collusion behavior exhibited by "free agents" in a limited pool; even without communication, the self-interested incentive to all follow a convergent rule will eventually emerge. Whether it be price fixing, social norms, or any other system where partially-regulated complex systems compete.
Additionally, for cannibalizing to be a positive-selective-trait, the species would had either adapted to eating the liver - the "resilience/filter" of a system, or had been "lucky" enough to identify/delineate/get repulsed by it.
Eating your own species liver would be nearly self-defeating-ly impossible from an evolutionary point of view and avoiding it but still eating your own species is too "taboo" (evolutionary artifact) of a benefit to ever randomly stumble into, especially against the benefits of 'good-sportsman-ship'.
> it is not generally advantageous to actually hurt the opponent more than needed to signal dominance
It is advantageous to beat a rival and take their energy even within a species. That's part of the whole 'survival of the fittest' thing. Preserving them for cooperation or something like slavery happens, but it's a rare strategy specific to intelligent animals like the GP implies.
As Dawkins points out in `Selfish Gene`, it's the DNA sequence that's the evolutionary entity. For example, all mothers (and most fathers) protect their young even though it's a food source. Eating your own species (even children of other mothers) is counterproductive for the DNA itself, despite being productive for the particular copy of the animal doing the eating.
I should had clarified, this is lower, more intuitive behavior. It is not, which is why it arises emergently in lower-complexity/class systems.
Beating a rival and taking their energy is awesome!And if done with literal, figurative, social, and complex "CLASS", it is literally sexy too!
National Geographic is entertaining for many dimensions of reasons.
Actually dismembering your sexual-rival and literally consuming their poor caloric conversion is pitifully inefficient compared to making them a sub-ling, whether it be via hen-pecking or innate dominance. It made sense before sexual dimorphication (moreso), but less so now.
Ladies like a gentleman, and gentleman's agreements are literally non-colluding emergent behavior to abide by unspoken higher-order rules for one's own explicit conscious self-incentive (lower order, high entropy), but also the implicit collective unconsciousness incentive (higher social order, lower entropy)
Both are reslience traits, which only emerge when selected for.
I have no idea what you meant by liver. Maybe it's a biology term I'm unaware of. Certainly you didn't mean the organ. lolz.
Anyway, an interesting point about evolution is that things had to have been eating other smaller things long before the brain had enough processing power for "Species Recognition". It would've initially been a simple brain and rod/cone eye neuron and motor neuron in a fish that executed primary the rule of "See movement then execute tail wag, open mouth, close mouth" in that order. It takes like 5 neurons wired in a specific way to accomplish that. The first neurons had to have been that simple. Indeed the chain reaction of "input photon and convert energy into motor neuron charge potential" had to have been the actual chemical process that eventually developed the first neuron to begin with.
It was only after MUCH more evolution that avoidance of eating one's own species would've been possible by visual inspection of the prey. However, it's true it could have been a 'taste' signal where the scales of your own species had a bad enough taste that you spit it out rather than eating it, and that can be accomplished also with a brain of only a few neurons.
Liver/kidneys are organs where toxins are filtered, from the prey the predator consumes.
I am not a biologist obviously.
Because of the "food chain" actually being a pyramid, those organs contain the same "toxins" that are to be avoided, exponentially accumulating in whatever "organ" had the function to add resiliency by storing these toxins.
Oh, I see. You expected people to infer "toxins" from the words "resilience/filter". Got it.
However, liver eating is a moot point regardless, because evolutionary theory would suggest eating toxins would have a bad taste/smell, so that organ would simply be avoided, while eating the rest. So it has no bearing on whether cannibalism happens or not.
We have nothing but confirmation bias and little time to test anything macro.
However, we do have contra-positives and the like; in this case, we (ourselves) avoid Liver in some animals, and notice the M.A.D-avoidance agreement among more socially-complex systems.
You shouldn't eat your young, you should eat your rival tribes young.
Especially because the young hand't accumulated much toxins yet, relative to the adults. And it is easier to bash babies over rocks than grown adults.
(per Carl Sagan)
yes, Q.E.D; the ambiguity of our lingua franca can be an "accumulate toxin" of sorts when trying to articulate higher-order ideas, as words (especially used as analogies) can carry implicit deprecated weight, and without the resilience of good-faith inference, can lead to misunderstandings, mis-alignment, or walking/talking write/right past each other.
--or-- yes, when someone writes a very unclear sentence and then blames the reader for not understanding it...even going so far as to accuse the reader of bad-faith motivations.
Did we both edit our posts....to improve accuracy, increase resiliency, and to compete ideas?
literally mesa-Q.E.D.
You edited your post after first insulting me, then deleting the insult. Yes I saw it, but I removed my acknowledgment of the insult, only after you removed the insult. But you weren't done yet...just taking care not to have "flaggable" wording. Now it's more stilted language and Latin FTW. Did I miss anything?
nope, just demonstrated my point further-er-er:
neither of us had the incentive to either acknowledge our edits nor call the other out,
nor face the (perceived, social, higher-order) dissonance of being slightly unclear or "wrong" due to our own ego/self-interest (conscious, lower ordered self);
the emergent behavior then (gentleman's agreement) was to preserve our own ego's and not call out each other edits - which most people would never do, because:
our slightly varied ideas compete more fiercely for the same finite pool than other, completely niche-unrelated abstractions.
we are 4 layers deep now, but ill reduce for conciseness (for lurkers fwiw)
dont shit where you eat <- evolved trait to avoid waste-by products
dont hit a man when he's down <- highly effective altruism is still beneficial
morality is cowardice <- ties this all together from highest order (ego) to the id (fear of being replace)
we are now full circle.
And now back to reality: I only edit posts to add an important point or fix a typo, but you edited your post to remove the insult it initially contained.
The insult was my inference that we should assume good faith, and that you had not done so (provably, by your 'lulz' snark); which you clearly did not show when assuming something other than the "liver" would be a organ of filtering toxins.
A decently display of faith should at least warrant a re-parsing of my (actually perfectly unambiguous) grammatical clarity, of which you implied was less than so.
Warrants the question, why not admit my posit:
People aren't intimated by people that cannot replace them, they are by people that can.Take it from Roko the Replacer:
But somewhere between a middle school drop out and a super-intelligence and 5-layers QED, I think my posit has merit.Free to continue discussion; but the under the Ego lies the Id, and I'm not well versed in that science yet, still approximating.
The crux of the misunderstanding was that you assumed any reader would know a reference to liver is a reference to "toxicity" apparently based purely on the nearby words "resilience" and "filter". That was a flawed assumption, and ambiguous unclear writing.
Artifacts of evolution such as tribalism/xenophobia are the most obvious examples/analogs.
But really, and "slightly" varied instance of yourself is the "most" likely to compete for the same, infinite pool of resources.
The second sentence of the comment.
The success of birds, bees, trees, plankton, mammals and so on. Many life forms have been rendered obsolete when the right adaptation comes along and forms a new branch.
Does it yield a rare Earth? If we didn't have mitochondria and had something say 20% less efficient, why couldn't multicellular life still exist?
> why couldn't multicellular life still exist?
We don't know the fundamental energy requirements of complex life. The threshold may be 2%. It may be 19.995%. If non-mitochondrial metabolism is common, the Earth would still be rare in that we'd be the "fast" biosphere. The high-octane species. Given how power-intensive intelligence is, that might be material. (Or it might not.)
More fundamentally: we have no plausible alternate chemistries that don't bootstrap on mitochondrial life. (We do for photosynthesis.)
> Given how power-intensive intelligence is
I’m not convinced there’s a reason to think intelligence is inherently power-intensive. Based on our limited samples, it’s certainly energy intensive, but there’s no reason it couldn’t be slowed down. In a world with less power available to life, one would expect speeds of e.g. predators and prey to be slower, allowing a slower intelligence to still provide an advantage.
> not convinced there’s a reason to think intelligence is inherently power-intensive
Sure. But we know it empirically is. Our brains are expensive.
> Sure. But we know it empirically is. Our brains are expensive.
But our brains have mitochondria. As do our prey, and our predators. Is there any reason to suppose that the absence of mitochondria implies less potential for intelligence, instead of the potential for equal but slower intelligence? Mitochondria are about power production, not energy production -- they are a very dense source of ATP, but the reactions they use would provide equal energy even if less concentrated.
I think that's a little farfetched since a lot of prokaryotes show the beginning stages of complex multi-cellularity.
I don't understand why anyone would commit to so adhering to a speculative hypothesis H as to call themselves an "H-er", especially one so pointless and vague as "Rare Earth". There is some probability that a random star has intelligent life on orbiting planets, but we have no idea what that probability is. The original "Rare Earth" proposal suggested that the Earth may be the only such planet in the galaxy, but at that rate there could be hundreds of billions of Earths.
> There is some probability that a random star has intelligent life on orbiting planets, but we have no idea what that probability is.
100%. The evolutionary pattern of our solar systems formation and earth ending up, temporarily, in just the right spot isn't rare but (was) a matter of time/timing.
Now one could argue that the stellar objects carrying specific components necessary for life did not hit every or many solar systems but every single simulation (in my head) of the big bang's aftermath reveals that it's at least multiple hundreds of thousands, given how much the observable universe has revealed so far in the places that we looked.
Mitochondria seems to have been an 'accident', yes.
That does not mean that other lifeforms in different planets require mitochondria or equivalent organelles. As long as they can perform the necessary chemical reactions (which could be different in a different environments) and extract enough energy, they should be good.
How did mitochondria evolve in the first place? Could they have remained as independent organisms and use their massive energy budget to evolve independently?
> long as they can perform the necessary chemical reactions
That mitochondria are conserved as an independent organelle across almost [1] all eukaryotes, across billions of years of history, suggests this is something the nuclear can’t easily in house.
[1] https://pmc.ncbi.nlm.nih.gov/articles/PMC6343361/
Maybe!
That could also suggest that any other strategies were just out competed by this one and lost the opportunity to develop further.
> other strategies were just out competed by this one and lost the opportunity to develop further
Absolutely. It also means--however--that any niche where alternative did exist, when exposed to mitochondrial life, they lost.
Now that I think about it, it would be pretty funny if we're this universe's cheela [1], a freakishly overclocked biosphere that runs faster not because it had to but because it happened to.
[1] https://en.wikipedia.org/wiki/Dragon%27s_Egg
Evolution is path-dependent. Notice that mammals were comprehensively outcompeted by dinosaurs till asteroid removed them and gave mammals time and niches to develop in. If you recreated dinosaurs right now they would lose to mammals (for example to homo sapiens).
It's perfectly possible that mitochondria are the dinosaurs of "cell powerplants" that just haven't encountered the asteroid to let other (ultimately better) solutions develop.
https://en.wikipedia.org/wiki/Monocercomonoides
>It is the first eukaryotic genus to be found to completely lack mitochondria, and all hallmark proteins responsible for mitochondrial function. The genus also lacks any other mitochondria related organelles (MROs) such as hydrogenosomes or mitosomes. Data suggests that the absence of mitochondria is not an ancestral feature, but rather due to secondary loss.
There are organisms without mitochondria too though. So it’s viable.
> are organisms without mitochondria too though. So it’s viable.
True, it's an anaerobic ersatz cnidarian [1] that may be an escaped cancer [2].
[1] https://daily.jstor.org/who-needs-mitochondria-anyway/
[2] https://pmc.ncbi.nlm.nih.gov/articles/PMC6343361/
> [discovered in] gut bacteria from a researcher’s pet chinchilla
wow. we could be surrounded by so many extraordinary organisms and not even know it because there's so much variety just in our own backyards
There was a study where participants were asked to swab their belly buttons and lots of new organisms were found.
https://www.theatlantic.com/health/archive/2012/12/1-458-bac...
Absolutely fascinating. Especially the exotic multicellularity part. Maybe if it evolves even more multicellularity it will struggle with cancers of its own and have to reevolve tumor suppression, wouldn't that be something?!
The benefit of mitochondria is in the isolation of the high power reactions, that involve chemically aggressive elements, from the rest of the cell. That allows for high energy throughput without self damage. Cells that do not have mitochondria run the same or analogous power producing reactions, but at a much lower volume, to keep the damage sustainable. An alternative option to mitochondria would be to evolve some means for isolation of the power production.
Mitochondria are bacteria that were endosymbioticized into what became the eukaryotic cell. Mitochondria can still survive (live) independently and functionally in the blood when they're separated from platelets and microvesicles. Mitochondria are the software that epigenetically switch nuclear DNA genes on and off. That sofware can be tweaked by light, for instance UV light or IR light. mtDNA mutates x1000000 more rapidly than nuclear DNA.
uhh where did you get " Mitochondria are the software that epigenetically switch nuclear DNA genes on and off."
> Could they have remained as independent organisms and use their massive energy budget to evolve independently?
There are independent mitochondrial relative. They are mostly parasites that live inside cells.
From https://en.wikipedia.org/wiki/Mitochondrion
> The proto-mitochondrion was probably closely related to Rickettsia.
From https://en.wikipedia.org/wiki/Rickettsia
> Being obligate intracellular bacteria, rickettsias depend on entry, growth, and replication within the cytoplasm of living eukaryotic host cells (typically endothelial cells).
> Most notably, Rickettsia species are the pathogens responsible for typhus, rickettsialpox, boutonneuse fever, African tick-bite fever, Rocky Mountain spotted fever, Flinders Island spotted fever, and Queensland tick typhus (Australian tick typhus).
One interesting thing is that many reactions actually have to occur in their own compartment- and since we have not lost the mtDNA, it may suggest that having an additional control center is beneficial.there are some interesting theories about the relations of that to lifespan https://www.cuimc.columbia.edu/news/mitochondria-are-flingin....
Couldn't it be that we haven't fully lost mtDNA because it's simply a very slow process that has not yet run its course?
Given how old mitochondria are it seems more likely that its more efficient to have its own DNA.
DNA isn't just abstract information, it's also where the first step of protein / enzyme construction occurs. DNA location matters.
> Could they have remained as independent organisms and use their massive energy budget to evolve independently?
This presumes that their energy budget was massive to begin with, rather than being selected for over time.
It's more that cells can have large numbers of mitochondria than that teach produces a large amount of power. Prokaryotic cells can grow large, but because they respirate over their surface they are energy limited.
Mitochondria allowed who different energetic regimes and structures. Like the scaffold that allows multicellular organisms to even hold together simpler are not possible (energetically) without mitochondria. It took the whole marriage of the two systems to allow the energy state (the "chemical reactions" as you say) to be possible
SFI Complexity podcast has a few great episodes on this
Right, the requirement for life is an entropy gradient sustained long enough as well as the right materials present to capture that.
It’s so pathetic to keep hearing that dna is an accident , life is an accident, mitochondria is an accident. What is an accident that natures says “oooops”. When will we take our heads out of the sand and realize the universe is alive and creating everything. There are no goddamn accidents !!!!
What? When saying that "X" is an accident, nobody means "nature says 'oooops'. Nature is neither conscious nor alive, if universe were alive and creates and shapes life, why is there so many errors happening in the universe?
Everything exist by " accident", and that means that is the result of random events that happen unexpectedly in unimaginable places, leading to an environent were the outcome of this events causes more random events.
Why universe insist in making life so uncommon if it has the secret to create and replicate?
People whose heads are out of the sand reject that misunderstanding of the universe and nature, neither of which are agents.
all happy little accidents!
Like other gradients (heat, pressure, chemical) it might seem rare, the gradient guides its occurrence. A power efficiency gradient was going to happen eventually, accident or otherwise.
Yup. That it happened isn't by chance, but the particular instance being the one to happen & dominate is by chance.
I may be wrong, but I recall reading recently it had been found the same event had occurred again, fairly recently (hundreds of thousands of years, could be millions) in some species of bacteria or something like that.
Here's a thought, also; maybe once this has happened, it tends to crowd out needing to happen again.
> it had been found the same event had occurred again, fairly recently
Would love to know the source if you have it.
Might be referring to this: https://newatlas.com/biology/life-merger-evolution-symbiosis...
Huh. This is the correct news, but a different article to the one I recall. However, very interesting;
> The first occurred about 2.2 billion years ago, when an archaea swallowed a bacterium that became the mitochondria.
> The second time happened about 1.6 billion years ago, when some of these more advanced cells absorbed cyanobacteria that could harvest energy from sunlight.
> And now, scientists have discovered that it’s happening again. A species of algae called Braarudosphaera bigelowii was found to have engulfed a cyanobacterium that lets them do something that algae, and plants in general, can’t normally do – "fixing" nitrogen straight from the air, and combining it with other elements to create more useful compounds.
So, tremendously rare, at least to our knowledge at this time, but not a one-off.
Yes. That's the one. Thank you.
Chloroplasts also evolved from separate organisms and are now effectively organelles. So this is t a one off event.
And even if those hadn't become organelles, who knows if they (or mitocondrias) could have evolved towards multicellular life on their own? They were already organisms to begin with.
Yes! and there are additional cases, like the nitroplasts that we recently discovered. https://en.wikipedia.org/wiki/Nitroplast
All planets with a diverse chemical makeup will stumble across accidental formation of a replicator molecule. It's 100% certain. That's all that's required for "life".
People have theorized even a 50 base pair segment of RNA might be capable of building exact copies of itself, either by snapping in half and auto-forming the same other half, or by other means. Since there's two sexes, it was perhaps a "halving" at that level, that early on, which led ultimately to TWO sexes, but that's a side point.
We can even predict the probability of any 50 base pair ordering. It's 1/(4^50). That's 30 zeroes in the denominator. Now consider that a single glass of water has 10^23 molecules. That's 7 orders of magnitude difference. So the amount of water you need to cross that magnitude threshold is 7. Turns out that's exactly the size of an Olympic swimming pool. 10 million cups of water.
So statistically, a planet with an ocean volume only as large as a swimming pool has the "Statistical Power" (power of large numbers) to find ANY 50 base pair combination (give or take an order of magnitude or two) Once it finds a replicator, life has started, and so has evolution. And that's guaranteed within the first minute or so, at reasonable temperatures. Now multiply that time by the average age of a planet, and you begin to realize, statistically life is guaranteed, in any chemically diverse scenario with reasonable temperatures.
Interesting argument, but nobody believes that a diverse chemical makeup is sufficient to guarantee life.
You can wave big numbers around but none of that makes a convincing argument; it's not hard to construct any number of scenarios where self replicators are started but don't lead to true life.
Also you're comparing a gram of water to a bunch of bases; H2O is not DNA.
Sure we don't have proof that all life will form from essentially "binary" data, (although technically ours is made of 4 bases, not 2), but it's almost axiomatic that life will find the simplest possible way to store information before it finds the more complex ways. Ergo DNA is almost binary, but quarternary instead. It's nearly digital.
Insofar as your H20 vs DNA comparison, I merely used water as a way to show relative "scale". That is, HOW MUCH fluid volume (relative to the order of magnitude of size of atoms) would it take to contain the requisite number of RNA. Because when it comes to probabilities of finding astronomically unlikely combinations, astronomically large numbers is key. I think in a mole of random Rubicks cubes, hundreds will be "accidentally solved" (I forgot those numbers, so check my math, on that one)
The reason I threw in the "give or take 2 orders of magnitude" caveat was precisely because I knew someone like you would accuse me of relating H20 to RNA in a way in which I didn't. Other planets will have different atoms, not necessary water-based life, but planets even the size of a swimming pool have the "numbers game" power to create life.
Are you aware that at high concentrations, DNA, RNA, and proteins all have serious problems? For example, DNA and RNA are highly charged, with strong repulsion effects, while also having large greasy areas. At the concentrations you're describing, the DNA and RNA would not be functional as we know it.
Right. The "thought experiment" math is a tight packing of theoretical RNA molecules, and not intended to be taken literally, without a dilution factor; but only to show [some] people their intuition is WAY off about the power of large numbers to "create" unlikely patterns.
For example, if you ask most people how many randomly occurring Rubiks Cubes will just be accidentally solved even with Avogrdro's number of them, their answer is usually zero; and unsurprisingly they're the same ones claiming there had to be a God to create even the initial replicator.
For this to hold, each of those water molecules in that swimming pool needs to somehow turn into a random 50 base pair chain of RNA.
Those RNA molecules are also going to be ~two orders of magnitude larger than a water molecule, so you're going to need a bigger pool...
To actually replicate, some loose ingredient molecules must also be present, and in reasonable quantities to be at hand in any given place in the pool.
The argument you are actually making is that a vessel that is filled with randomly assembled chunks of RNA not shorter than 50 base pairs each, the quantity of which equal the number of molecules of water in an Olympic pool, would contain life with probability ~1.
Now, the ocean is large, and a billion years is a long time, but I'm a long way from convinced that the chance of life is 100% on any given suitable planet.
That's a decent analysis of the things this "thought experiment" doesn't address. I'm not a chemist but I think in a sea of AT and GC pairs even mixed with water, the ability to find every random sequence possible is near certainty:
Especially when you multiply by the number of swimming pools of all ocean water (10^14) by the number of minutes of the history of Earth (10^15), and consider that the probability of the accidental 50 base pair replicator forming needs to have those 29 extra zeroes, in the numerator (not the denominator). So the likelihood, now that I add more info, has just gone up 29 orders of magnitude. lol. (BTW. the 1 minute assumption will be temperature dependent, and is a guess at how long it takes reactions to take place).
The whole thing is a rough approximation like the Drake Equation is, and each number is an estimate. If you want to attack the Thought Experiment, at it's weakest point, just question the initial assumption, which is the biggest guess of all, that some unique 50 base pair RNA can replicate itself.
There are a huge number of different organelles that evolved independently through events like this- other people mention chloroplasts but there are many others, and probably many yet undiscovered.
I would argue that the type of event that produced mitochondria is likely not rare at all, but certain pairings will so outcompete others that we should expect only one to survive and dominate.
I have a chloroplast for you on line two; can you hold?
They're sensitive about the Oxygen Holocaust [1][2]?
[1] https://en.wikipedia.org/wiki/Great_Oxidation_Event
[2] https://en.wikipedia.org/wiki/Purple_Earth_hypothesis
> Moreover, there may be a narrow window where it can happen: modern microbiology has defences and selection pressures that it make inhospitable to the hobbling chimeræ the first mitochondrial cells would have been.
I don't think it is a very persuasive argument, because it is possible that modern microbiology has defenses because it has mitochondria. I know almost nothing about cells from a few billions years ago, but it seems plausible to me that they were ambivalent towards intrusions of other cells, it can be beneficial or disadvantageous depending on an intruder. Moreover beneficial intruders could give a lot of evolutionary advantage, not like today, when all important things (like mitohondria) are already here. In theory, bacteria could benefit a lot, but there are no ecological niches for a bacteria with mitochondria, all are claimed by some eucaryotes, which are highly adapted.
It is a very common thing in evolution. For example, there are bats, but they cannot evolve and replace birds, because there are birds. Bats have their niche, but they cannot outcompete birds at being more birds than birds. If they were given a chance, then maybe they could try to catch up with birds, but they didn't have a chance and they will have it only if some cataclysm will wipe out birds and leave bats.
If reality can emerge out of nowhere I don't see it unlikely for life to emerge in some other planet.
> If reality can emerge out of nowhere I don't see it unlikely for life to emerge in some other planet
If everything however unlikely is likely because creation is unfathomable, sure.
Not everything. Life in particular. Because without life (a conscious observer) reality cannot exist. So it should be a property of reality for life to emerge.
Isn't that kind of mixing up the chain of causation? Without a winner, a lottery cannot exist (or at least, at p=0, it's nonsensical). That doesn't automatically imply there are a lot of winners, however.
I think what I am trying to say is consciousness (life) is reality. And so all kind of planetary experiences can exist inside consciousness as it's contents since consciousness is capable of generating all kind of content.
There is nothing specific about our consciousness that makes it unique to earth.
Your philosophy is consistent with panpsychism (https://en.wikipedia.org/wiki/Panpsychism). Not really clear how this affects the major discussion here, which is about objective reality as determined by science, and so far as we can tell, neither life nor consciousness is not a prerequisite for reality. It's a fun idea to play with but firmly outside the realm of something we could experiment with scientifically.
You are mistaking the map for the territory: https://en.wikipedia.org/wiki/Map%E2%80%93territory_relation
Can you explain in simple terms? I see physical reality as almost redundant and consciousness seems to be able to do everything.
From the first paragraph of the linked article:
"Mistaking the map for the territory is a logical fallacy that occurs when someone confuses the semantics of a term with what it represents. Polish-American scientist and philosopher Alfred Korzybski remarked that "the map is not the territory" and that "the word is not the thing", encapsulating his view that an abstraction derived from something, or a reaction to it, is not the thing itself. Korzybski held that many people do confuse maps with territories, that is, confuse conceptual models of reality with reality itself."
Okay. I can see that in day to day life. People confusing sentences with actual knowing. Like labeling something a tree and thinking you know what a tree is because you know it's a "tree".
But how did anyone verify there is an underlying reality outside consciousness? It's just an assumption right?
Yes, it's taken on faith by scientists that we live in an objective universe with cold hard reality outside our consciousness. It seems like a reasonable assumption, consistent with all our observations. It seems not unreasonable to assume that in the early universe there was nothing living, then at some point, through random chance, the first living things became alive (possibly from some non-alive replicators), and then later, the first living things with consciousness came to be. Again, all of this is consistent with our observations, but effectively taken on faith/treated as an assumption.
> But how did anyone verify there is an underlying reality outside consciousness?
It's the stuff which continues existing when we stop believing in it.
A 'quantum observer' is merely a physical system that interacts with the quantum system being measured. It doesn't have to be conscious or animate.
There is no known scientific principle or theory with experimental support that without a conscious observer reality cannot exist. It's not something that can be tested, and lies in the realm of philosophy, not science.
I don't think reality has this property that what cannot be tested through scientific method is not true.
It might not, you wouldn't be able to convince anybody that something is true, but cannot be tested- that's philosophy and religion.
I think David Deutsche has this idea that the best explanations should be treated as true even if you can't test it.
That sounds like a catch-22
Only if you assume it went the seemingly straightforward way, but it could have been more complex. Maybe at first there was no particular limit to unicellular life, and there were unicellular lifeforms both small or large. But the big ones had a terrible problem avoiding getting parasitized by microscopic ones. As, there is one wall to breach, and once it gets in, it's in for good. So maybe eventually one of the bigger ones developed multicellularity as a kind of internal defence wall system, rather than multicellular life evolving from tiny cells clumping together. This gave it an enormous advantage at larger sizes, as all pathogens had to invade the cells one by one, and most of the macroscopic unicellular organisms perished, and some unicellular eukaryotes evolved since then.
Robin Hanson #HardSteps
https://m.youtube.com/watch?v=0lKliaFllPA&t=910s (timeatamped)
Earth is so rare that there might merely be hundred of billions of others (say, one per galaxy).
There are a lot of sub Neptune planets, the reason why there are only a few earth alike planets is just lack of powerful telescopes and observation time. As technology improves, we’ll find much more planets like ours. Earth is not unique in any way
How do we know it only happened once? Maybe it happened multiple times but only one version survived while the others were outcompeted?
> How do we know it only happened once?
We don't. But we know we can't replicate it, have never observed it, don't seem to find half-assed attempts at it in the wild and that there weren't multiple competing chemistries that found themselves co-existing, there was one.
I would like to present you with Chlamydia.
I find it remarkable that chlamydia cells, fully enter host cells and live there stealing of resources.
I would call it evolutions “half-assed attempt” at endosymbiosis. (Disclaimer: evolution has no goal)
I know nothing about biology, pardon my ignorance. From the article it sounds like mitochondria were a separate organism that has perhaps simplified through specialization and is currently on the boundary of being an independent life form. It also sounds like there are other structures (golgi apparatus are mentioned?) which are not on the bubble. Are we sure that there is not an arrow of time here, where once those other structures were also semi-independent and have become less so?
More broadly, it leads me to wonder whether cellular life might eventually/might have at some point specialize towards hosting novel endosymbioses.
Either scenario, assuming what I'm saying isn't just total nonsense, would seem to make the state of mitochondria less of a one-off event and more of the instance of that event we are around at the right time to observe.
Hi! thanks for taking time to read :)
Those other membrane bubbles inside out cells don't have any of the machines we expect to be associated with cellular life- but you never actually know!
Also, this is def not a 1-off, and happened many times, including chloroplasts in this new nitroplast we found https://en.wikipedia.org/wiki/Nitroplast
So only a few billion planets with complex life?
> only a few billion planets with complex life?
Or trillions or tens or ones. Depends on what number you put in the exponent. Currently, we don't have useful constraints on that figure.
(A lot of popular astrobiology pulls the "if we could only get 1% of the market we'd be billionaires" schtick.)
The astrobiology schtick is just a what if thought experiment though, and nothing proven nor claimed to be fact. It's just a way to show that the scale of the universe is "hugely, mind-bogglingly big" while trying to pull a number that our squishy lobes could comprehend. If 1% of mind-bogglingly huge number, then 1% of that, then 1% of that yields a still mind-bogglingly big number. The laws of large numbers would suggest something as well. Otherwise, "its an awful waste of space"
Sure. The point is 1% is a huge fraction for a lot of things. Market share. And many reaction cross sections.
This article managed to hit two classic science journalism cliches in just the first few paragraphs.
(1) “Someone hypothesizing a very dramatic theory with weak evidence was considered wrong by most colleagues but later vindicated when strong evidence emerged”. (No mention of thousands of other dramatic hypotheses that turned out wrong.)
(2) “You may have heard in unsophisticated popularization that [philosophical claim ultimately hinging on semantic distinction] was false, but really it’s true [assuming my preferred semantics]”.
Aren't we all tired of this yet? Aren’t science journalists embarrassed by this stuff?
For #1, I disagree with how you assess this.
Firstly, the one who makes the logical fallacy inference that this implies all or most dramatic hypotheses are true is ... You. Not the author of the article. The author of the article is only talking about one specific theory. If I tell you a story about a chicken crossing the road, I'm not obligated to tell you about all the chickens who don't cross any roads.
Second, there are plenty of examples of established theories that started this way, and so it is important that scientists consider controversial hypotheses with an open mind. Speaking in any context, it's very easy to dismiss evidence that contradicts your views prematurely. It's sort of a defense mechanism we all do. It's important to recognize such a bias and be willing to acknowledge where your own theory could fall short when you see it.
My point isn’t that these can’t be interpreted correctly, it’s that these framings teach us nothing new because they have been repeated a thousand million times and this article does not attempt to go beyond the superficial cliche.
Hi! for point 2# I had many debates about this with Prof. that are cell biologists, and if you google "Are mitochondria alive," the answer Gemini will give you is no. This is very controversial in my academic circles, but I appreciate your thoughts!
My point is that it’s largely a semantics dispute, not a scientific one.
Perfectly put
>No mention of thousands of other dramatic hypotheses that turned out wrong.
In other news, Local Man Didn't Win Lottery
Any time I read a mitochondria post like this, I strongly recommend that others who find the topic interesting check out Power, Sex, and Suicide by Nick Lane.
Excellent book!
+1 to Nick Lane
I’ve only read The Vital Question, but I felt it was a great introduction to biochem for someone not in the field.
Absolutely loved TVQ. The insight about mitochondrial DNA inheritance being exclusively from the mother, thus motivating female fingerprinting of male nucleic DNA for gamete viability (via courtship rituals, pheromones, plumage, etc)...
The Vital Question covers this topic and is in general a really great basic education in biological energy production.
Came here to recommend Power, Sex, and Suicide. It is a fascinating book.
>Defining mitochondria as “nonliving” isn’t just a classification mistake, nor a question of word choice. Rather, it is a fundamental misunderstanding of the nature and role of mitochondria. It inherently undermines our understanding of biological systems and deeply influences the tools we build to study them.
This assertion is made but not supported. I don't think I understand the importance of this distinction, assuming that everyone already agrees about the evolutionary and mechanical facts about mitochondria, but as far as I can tell, no one disagrees that mitochondria were originally free living cells, or that they have their own DNA, or any of the other relevant facts about their origins or how they work in the cell. It's merely an argument about what it means to be alive. Which is philosophically interesting, but practically unimportant for the practice of biology.
This seems like a purely semantic debate with no broader importance.
From an article cited in the OP [0],
More than 95% of all proteins located in the mitochondrial compartments are encoded by the nuclear DNA, synthesized in cytoplasmic ribosomes and imported into mitochondria. These include factors that regulate mitochondrial DNA (mtDNA) gene expression such as mtDNA and RNA polymerases, mitochondrial transcription factors, RNA processing and modifying enzymes, transcription termination factors, mitochondrial ribosomal proteins, aminoacyl-tRNA synthetases, and translation factors (1, 2).
It's clear that a mitrochondrial element can't live for long without the presence of the host cells, so, like a virus, it doesn't meet all the requirements to be considered fully living.
[0] https://pmc.ncbi.nlm.nih.gov/articles/PMC23071/
I read the article waiting for an answer to the question "in what operational sense does this matter?" but it never arrived.
The question posed is whether we consider mitochondria to be "alive". It's just a word, who cares. What do we do differently given this assumption?
> Defining mitochondria as “nonliving” isn’t just a classification mistake, nor a question of word choice. Rather, it is a fundamental misunderstanding of the nature and role of mitochondria. It inherently undermines our understanding of biological systems and deeply influences the tools we build to study them.
Once you accept mitochondria as alive, you might be motivated to explore its "potential" niche, as described by the author. The example of implanting cross-species mitochondria in human cells (e.g. from a gorilla) might lead to novel therapies.
It's about breaking outside the box of mitochondria having to live inside specific environments.
I recognize that you might be motivated to explore removing and implanting mitochondria regardless of whether you consider it to be alive (as you might think about implanting an organ from another source).
I think the main point the author is making is to not fall prey to reductive thinking about mitochondria's potential and less about the question of "aliveness". We were all taught about mitochondria producing ATP, but it sounds like it serves many other functions and there's a lot more to explore about its potential in synthetic biology and therapeutics.
So the theory is that if we don't accept them as alive, then we can't experiment with implanting cross-species mitochondria in human cells? Why not? What stops us from doing this?
This is a fair point. I can see the excitement around recognizing that mitochondria is alive to motivate exploring its other functions. But I think you're right someone might be interested in that exploration regardless of whether it's considered alive.
Edit: to your point, there are plenty of scientists interested in studying viruses and much debate about whether or not they are alive. Ultimately it probably doesn't matter.
I do think when you consider mitochondria to be alive, it broadens the scope of your thinking because you start considering each characteristic of life in relation to mitochondria. You might not be motivated to do that without thinking in those terms.
It doesn't seem the article addresses this, but I'd ask these questions: "would it be possible that mitochondria's evolutional interest and the organism's interest are not aligned?" "how many independent DNA can an organism possess?" "why mitochondria do not elicit immune reactions? Or can they?"
1) https://en.wikipedia.org/wiki/Mother%27s_curse
2) By "organism" I assume you mean "cell" since humans have several thousand different species with their own DNA living on or inside the body at any given moment. We can speak of animal cells, which have two (species and mitochondria) - and plant cells, which have three (species, mitochondria, and chloroplasts). If there can be one two or three, I don't see why there couldn't be even more.
3) Mitochondria are usually sequestered within the cell, which limits their exposure to immune cells. The immune system primarily targets pathogens that are outside the host cells. In fact, some pathogens can exploit mitochondrial pathways to evade immune detection - the most famous of which is HIV.
Thank you for these amazing answers. Mother's curse is a notion I had no idea of, but it makes sense now that I think about it.
And chloroplasts have separate DNAs from the species ones? That really is also eye-opening.. Biology is full of wonders.
It matters for a number of reasons, but the main reason in terms of pure biology is that it was not originally recognized that cells could absorb other cells and utilize them for the absorbed cell's natural function.
This meant, importantly, that we learned cells did not always need to evolve a functionality from scratch, but could acquire it through phagocytosis.
It's also a useful tool for studying evolution for many reasons.
Whether or not mitochondria were once viable independent organisms that were absorbed by early eukaryotes does not depend on whether we call their modern descendants "living" or not. If we determine that they did, then we still don't have to call them alive -- certainly things like mitosomes exist and are suspected to have either evolved from mitochondria or evolved after amitochondrial division, but do not have DNA and do not reproduce independently but fulfil similar functions.
We know they have DNA, we know they reproduce independently of the host cell, we know to a degree why they tend to move to both sides on cell division. We know lots of stuff about them and we can always learn lots more. Whether they are "alive" or not has absolutely no bearing on that, other than to naval-gaze.
Oh, I see, you're getting hung up on the use of the term alive for modern mitochondria.
This sort of definitional argument is not interesting to me.
I think we're in agreement then -- this article is not about "did mitochondria evolve from absorbed viable organisms as opposed to evolving directly", which is an interesting question that impacts our understanding of evolution in microbiology. The article is about whether "Microchondria Are Alive" which is a useless naval-gaze.
I dunno if I agree it's a total navel gaze.
For example I could easily see a scientist asking the question, "if mitochrondira are not alive, at which point did the phagocytosis of the initial prokaryotic cell lead to the mitochondria not being alive?" "What components were lost in the cell that lead to the loss of life?" I agree these aren't particularly useful, and are ultimately definitional, but definitions matter a lot in science, especially when paradigms change.
This is a much more interesting question, and this is what I mean by an operational definition of life. In your first question, "alive" can have useful operational definitions -- whether it is viable outside of a cell, whether it has or had its own immune system and structure, how it survived without the organelles that other full-fledged cells seem to have but mitochondria lack, etc.
The question in the abstract is not really useful except to answer trick questions in bar trivia.
I was equally dismissive of the actual importance of philosophizing whether mitochondrias are alive or not, but this paragraph made me change my mind.
> It seems Mitochondria are not bound to their host cell; they can travel between different cells. Although different species carry distinct mitochondria, experiments show that mitochondria from one species can be transferred to another.
> In 1997, scientists isolated mitochondria from chimpanzees and gorillas and showed that they are naturally internalized and integrated into human cells. Notably, the addition of external mitochondria even showed therapeutic benefits in heart failure and spinal cord injury. Thus, the potential niche that mitochondria can live in is greater than their effective niche.
So it seems like they are more symbiote than organelle, that's amazing.
The question itself if just semantics. But considering our mitochondria as evolving populations subject to selective pressure and genetic drift is really important to understanding their role in our health, down to basic questions like "Why is exercise healthy?"
Exactly. Seems similar to "are LLMs alive"? What practical purpose would an answer to that question serve?
That seems to be an overly reductive view on the value of knowledge.
What practical purpose does studying ancient civilizations have? Why do we send expensive telescopes into space to study faraway galaxies and try to uncover mysteries of the big bang? When can we expect the results from number theory to lower the price of gas at the pump?
But the definition of a word is not knowledge.
Knowing that mitochondria have their own DNA is knowledge. Knowing that they reproduce independently of their home cell is knowledge. Learning whether they evolved from a separate viable organism would be knowledge. Learning whether we can make them viable, or breed them separately, and use them in therapies -- all knowledge.
Whether they are "alive" or not is just the definition of a word.
Much of science is about defining words in ways that match the underlying general structure of the system being studied.
A subset of scientists want to come up with an operational definition of "What is life", which may or may not include things like viruses and mitochondria. As you say, it's mostly definitional, but by defining this, we can potentially make our understanding match up with the latent reality.
Ew. That's always an uncomfortable read.
Random thought after reading all the philosophical and semantics tangents in the comments here:
A good example of a memetic equivalent of endosymbiosis could be Christianity - Catholicism in particular. Historically, as Christianity spread around the world over the two millenia, it would often adapt and absorb indigenous beliefs and practices of converted populations[0]. Many would die out over time, but some got integrated into the core and exported globally.
It's just the right time of year to think about Christmas[1]. Can you imagine Christianity without one of its two core holidays? That makes it probably the closest memetic equivalent of a mitochondria - you can still see in it the distinct outline of an ancient Roman festival that was absorbed early on, but all of its memes live on in Christianity. In our times, the holiday is vital to the overall faith, and itself could not exist independently[2].
--
[0] - I've always been taught that this was intentional slack to make it easier for people to accept a new religion, but nowadays I feel it might have been a fundamentally unavoidable outcome. Maintaining organizational coherence and belief consistency at a scale of a whole continent requires communication and bureaucratic technologies that didn't exist until the last 100-200 years.
[1] - Or at least so most shops would have me believe; in western commercial calendar, Christmas starts when Halloween ends.
[2] - Well okay, I admit this might be a weak part of the analogy - in the western world, Christmas got commercialized to the point it could likely survive as an independent secular tradition.
> Historically, as Christianity spread around the world over the two millenia, it would often adapt and absorb indigenous beliefs and practices of converted populations
Certainly, in the Eastern Orthodox church it's commonly called "baptizing the culture". The idea was/is to take what is good from a culture and to incorporate it to help people become Christians. Also it's a core part of Christian missionaries to learn the language and translate the scripture, and if needed to create a written form of the language.
So I'd agree Christianity has always been a bit of a symbiosis of cultures, analogous as you said to endosymbiosis. It started purely Judaic, incorporated large parts of hellenism, and spread globally and imported more bits. The Jewish and Hellenic pieces aren't completely mixed, sort of similar to a mitochondria actually.
Then again it makes sense of a religion with a core belief that God became man and created a symbiosis of the two as their savior.
Right but the way they did it to the Mayans was messed up
The fact that every child on the planet is religiously taught that the mitochondria is the powerhouse of the cell is all the evidence I need that we're upholding a primordial contractual agreement and these are the conditions to which we are beholden.
Name a single biological entity that has a better PR department. The only one that comes close is Athlete's Foot, which makes the victim sound cool.
I actually never heard the phrase until I got online and saw the meme!
My biology classes did have us gene editing bacteria to chance its color. That was fun!
> The only one that comes close is Athlete's Foot, which makes the victim sound cool.
The best cure for athletes foot is a 30 minute soak in diluted bleach. Get a wash basin, fill it with warm water, and add enough bleach so that it tingles a little bit.
Do this every other day 3 times, e.g. Monday, Wednesday, Friday. Problem solved.
Make sure to clean out the shoes as well, ideally not wearing any infected shoes for a few days at least, and soak the insides with Lysol a few times to prevent reinfection.
I have the same experience - never heard of it until I saw the meme. I have a feeling it’s something local to American schoolchildren.
Do the same but with Potassium chloride or bicarbonate. Done! And way safer
According to my doctor, this can weaken the skin too much. 30 minutes is quite a long time.
Depends on how diluted the bleach is. Also 30 minutes may be more than necessary, but it's what I've always done for athlete's foot. For other random crap that's tries to grow on my skin I'll dilute some bleach on a paper towel and let that sit on whatever is trying to eat me.
The basis of this technique is that you have skin to spare, and your skin regrows.
Unlike the fungus.
Unfortunately Jock Itch (the same type of fungus) didn't get the same PR treatment.
>"Name a single biological entity that has a better PR department. The only one that comes close is Athlete's Foot, which makes the victim sound cool."
Love this line! Phoenix Worm came to mind.
> the mitochondria is the powerhouse of the cell
The explanation doesn't get much better at higher levels. You have the Krebs cycle which biology people religiously memorize but it doesn't really explain much either. The actual interesting part is usually handwaved away as "magical enzyme/protein" catalysis. Understanding how the mitochondrial proteins/enzyme catalysts function would usually require a graduate degree, and maybe a background in biochemistry and biophysics.
If you haven't, I suggest you look up an on how ATP Synthase uses the proton gradient to create ATP. It's quite amazing. It's literally a little nano-machine.
The Sun.
As far as I’m aware we’ve never worshipped mitochondria. And unless you want to count eating which is technically true but not philosophically so, we don’t sacrifice plants or animals to mitochondria.
Not very biological though.
I don't know why but for some reason, the name Mitochondria is very easy to remember even though it sounds complex.
Excellent point.
Are there mitochondria in neurons?
Every cell in the body (except blood cells) has mithocondria.
Nitpick: except red blood cells. White cells very much do have mitochondria.
RBC's don't need them because they are incredibly low-metabolism. It's energetically cheaper for the organism just to make them, let them go for a few months, and then recycle the components.
> Are there mitochondria in neurons?
Yes [1].
[1] https://pmc.ncbi.nlm.nih.gov/articles/PMC7373250/
Yes. Neurons are very energy hungry.
Achilles tendon?
The brain gets good PR. The brain dead are thought unfortunate.
Key fact (left out of the article): most of the mitochondria's essential proteins, including those for ATP/energy synthesis, are produced by the host cell from the host cell's DNA. So yes, mitochondria have some DNA and do replicate, but no, their cell is not just an "environment" for them.
Also interesting: mitochondria can join (often to rescue one failing due to transcription errors) and be transported to other cells across bridges (to supercharge the recipient, as they want to do now for immune cell therapy).
It's such highly unlikely chance events that make me think we really are alone in the universe (we = a sentient civilizational lifeform). There's just no way the long series of extremely improbable events that led to our rise was replicated anywhere else, and it took the sheer vastness of this universe for it to have emerged even once.
There is ~1M bacteria in a single drop of seawater.
Now multiply that by (the ocean) and multiply the interactions by X billion years.
It seems impossible for a symbiosis like this not to have happened.
No matter how low the odds are, the counts of those potential interactions bring this outcome to a certainty.
Each grain of sand on earth represents 1 billion planets in the universe.
https://www.reddit.com/r/spaceporn/comments/1af4prs/if_you_w...
There are 100 million times more bacteria in the ocean than there are stars in the universe.
Which really should tell people how rare the development of mitochondria was if it has only happened once here.
It didn't necessarily happen only once; maybe we were left with the most successful instance.
Not even that. There could be better civilizations than us out there that either
1. Died off or regressed
2. Plateaued
3. Is sufficiently far away or stealthy enough for us not to notice them (whether intentionally or not)
I've often thought about the whole communications bubble argument... I don't buy it. I'd imagine, like wifi, other civilizations will maximize their communication bandwidth, which essentially also maximizes entropy which looks like noise to us. Compression, encryption, redundancy, multiplexing over frequency and amplitude and time, directional antennas and signalling... That's what we've done in under 100 years.
I know there's stuff like organic markers etc, but if machines are doing most of the heavy lifting I don't think that would matter. Same with stuff like hydrogen emissions lines. Whatever is abundant will be used for "settled" and "dead" solar systems alike.
This is a such common logical fallacy that we should have name for it.
> No matter how low the odds are, the counts of those potential interactions bring this outcome to a certainty.
"No matter how low", really? Are you suggesting that your multiplication result is infinite? Otherwise, no matter how big the result is—even if it's Graham's number or TREE(3)—but as long as it's finite, there are odds so low that bring the outcome extremely unlikely.
The thing is we don't know even a ballpark estimate of the odds, but you were saying like we have a lower bound of the odds. The universe is unfathomably huge, true, but we also don't know if abiogenesis is less unfathomably unlikely.
The issue here is that the interactions over X billion years are not the same. Each event that happened on this rock would also need to happen else where to have the same evolutionary pressures applied.
> No matter how low the odds are, the counts of those potential interactions bring this outcome to a certainty.
That is simply not true. Events are classified by probabilities, and there are a whole lot of things with a probability a lot less than will happen across the whole ocean across however many billion years.
All the higher-probability events will occur, yes. But a specific sequence of multiple extremely low-probability events? That then continues to replicate before it gets wiped out by chance?
Not a certainty, absolutely not. Contrary to what you say, it matters very much exactly how low the odds are.
The universe seems so ridiculously big to me that I can’t imagine anything major happening only once.
universe big
this is the first ive heard of mitochondria replicating separately and distinctly from the host cell, how fascinating!
Are we saying that mitochondria have their own life cycle inside of a cell? living/dying/replicating in the span of the "life" of a single host cell? When a host cell reproduces, how does the mitochondria get produced in the new cell to get things started?
Cant wait to research this later.
The two halves of the divided cells will usually both have mitochondria. Not always, though; sometimes cell division leaves one cell without any mitochrondria. That usually results in a non-viable cell, but sometimes the cell can survive with limited capacity. Some species that used to have mitochondria have apparently been through this process and have evolved to survive in their absence; Giardia duodenalis for example.
Oh wow! It never occurred to me that there are creatures without mitochondria.
https://www.science.org/content/article/first-eukaryotes-fou...
> When a host cell reproduces, how does the mitochondria get produced in the new cell to get things started?
Each half of the cell keeps the mitocondria that were living inside it.
I don’t understand the headline (yes I skimmed the article). Why would mitochondria not be alive? What does that even mean?
"If we think of mitochondria as non-living organelles..."
mitochondria were thought to just be a component of the cell. But they have their own DNA separate from that in the cell's nucleus. They replicate on their own like bacteria.
Organelles are alive too. All active biological systems are alive.
Mitochondria have for many generations now been known to have their own DNA and replicate on their own. So I’m not sure what new distinction is being drawn?
I _think_ what they mean is it's not typically listed as a "life form" in its own right, i.e., there's no Domain under which one would classify Mitochondria - maybe just calling them bacteria would capture the article's intent?
So, the modification would be that we are living in symbiosis with mitochondrial bacteria, similar to how we live in symbiosis with our gut bacteria, rather than them being classified as "organelles" of eukaryote cells.
Of course it is classified. In Wikipedia itself there is a phylogenetic tree listing its closest relative the alphaproteobacteria: https://en.wikipedia.org/wiki/Mitochondrion#Origin_and_evolu...
Yeah, the wikipedia entry is actually a good example.. it starts with
> A mitochondrion (pl. mitochondria) is an organelle found in the cells of most eukaryotes, such as animals, plants and fungi.
and the "classification" is introduced with
> There are two hypotheses about the origin of mitochondria: endosymbiotic and autogenous.
As others note, it is classified in the tree of life. We know approximately what kind of bacteria it evolved from, and mitochondria themselves constitute their own divergent branch of the tree of life (there are many longitudinal studies of mitochondria across species).
But if you wanted classify them based on functionality rather than evolutionary history, I'd say they're more like viruses. They have only a handful of genes themselves, and exploits the nucleus' genetic material for all the other proteins it needs to function.
That's more a flaw of classification systems though. Because even if they comprise a distinct life form does not mean they need to have a unique species. Consider lichen, which comprise two (or more!) separate "species" which becomes a meaningless distinction when they cannot survive on their own, or even if they could, not in a form recognizable in any wayas they were when they were a part of the symbiotic system
I mean at that point what do we consider multicellular organisms? Did you see what was going on with those frog skin cells and "xenobots"? Also, our gut bacteria kinda makes us a symbiote at a larger scale.
Depends on your definition of organelle (whether you limit it to plastids/mitochondria, both of which were derived from external independent living cells, or use a more expansive definition that includes more cell compartments that weren't derived from independent living cells).
General acceptance of the endosymbiont theory is a relatively recent (much less than 50 years) phenomenon.
"General acceptance" is a subjective criteria. But the endosymbiont theory is >60 years old at this point.
I was looking for specific notions explaining the emergence of this kind of endosymbiosis, anybody has links ?
> mitochondria were thought to just be a component of the cell.
... hundreds of years ago, for a short time after they were discovered.
We know that they behave like bacteria for almost as long as we know that they exist.
They "behave as" bacteria. Are they bacteria? Are they 'alive' by themselves? That's the distinction.
> Are they 'alive' by themselves?
That's a discussion about word semantics that has no relation to biology. Biologists have been occupied with it for centuries, just like computer people have lost time on "what's intelligence?", but neither one is relevant for either field.
> Are they bacteria?
Once upon a time, their ancestors were. I do not know exactly where biologists trace the line, but this is also about word semantics. It's just a case of it that helps people communicate better, so there is a line, I just don't know what it is.
What do you mean by "alive?" Because of course they are alive, regardless of whether you consider them bacteria or not. There is a strange definition of "alive" that is being used by you and the author article that I'm not understanding.
If a mitochondria is not "alive," then is it dead? Even if it is taking part in an active, living cell?
I imagine it's similar to how viruses are not considered to be alive, since they cannot reproduce without a host cell?
But I have never been a fan of that argument either, both seem alive to me.
I think the idea here is that mitochondria developed independent of cells and later lived exclusively inside of them. In other words, they reproduced without cells. I am not sure, please correct me if I am wrong.
You're not wrong. But over the enormous amount of time since, the "duplicate" organelles and systems needed for independent living were steadily carved out of mitochondria. While they do have their own DNA and replication process, the DNA is basically limited to specific things they need to perform their energy-generation functions and the replication happens when triggered by host cell replication.
It's a bit like if you took the heart from an animal and transplanted it into a human: is it meaningful to call it independently alive? Maybe, it depends what question you're trying to ask.
No, the predecessors of mitochondria were also cells and they reproduced through cellular division.
I don't know of any definition of "alive" that can survive application of a reductive understanding of biology that doesn't either count viruses as being "alive," or decide that nothing is alive.
The uncertainty, I understood, was whether to classify them as distinct organisms the way we classify other species, as they are intrinsically parasitic for their replicative capability.
Outside of a host cell viruses do not fit any of the definitions of life: - they do not seek or consume sources of nutrients or energy - they do not have a metabolism - they do not grow
In fact the only place they fit the definition is reproduction, and that is only through the machinery they commandeer from the cells they infect.
To me viruses clearly do not fit the definition of life. But fire... that is hard to exclude from the definition without some mental contortions. I am not advocating that fire is alive for any useful reason, but it is hard to exclude from the definition.
I am terrible at biology but I will try. The idea is that mitochondria is not a component of a living organism, but an organism that once lived independently of the cell.
Here is an animation of the Mitochondria in action. The mitochondria has two cell membranes. The gap in between is called the intermembrane space. It is also positively charged with protons. There are complexes 1-4 which continuously pump protons into this space. The ATP synthase molecule harnesses these protons, similar to a water wheel harnessing the flow of water, to make ATP which is the energy molecule the cell uses.
https://youtu.be/LQmTKxI4Wn4?si=i7TpeoV3o_mCWpZF
a lot of focus on the definition of "alive" in the comments, but i think that the weight of this rests on it being a step toward confirming the endosymbiotic relationship theory which states that mitochondria were potentially part of another eukaryotic cells carrying what would become mitogchodria were engulfed by another cell. this affected cellular development by outsourcing energy production for the cell itself. a lot of times the results seem "self-evident" but you still have to find evidence to support or reject a theory and this seems like a step in that direction.
I still think about the fact that we're this close to proving the protocell theory, proving that we can create life from no life. Last time I read about it was 2021, and I'm really curious when the day arises we succeed
They are obviously alive, but also we are obviously a colony organism. The various bacteria we transmit from mother to child, the mitochondria inherent to our cells, all of this stuff is just part of a self-similarity of life from top to bottom. With sufficient zoom-out, we need not treat individuals (or pairs) as the only unit of life replication.
This feels a lot like the debate about whether Pluto is a planet: what we're really trying to figure out here is whether we can figure out a definition for a concept that includes all the things we think should be included, and excludes all the things we think should be excluded -- and the meta conversation is: can we all agree on what should be included/excluded? That's a bit of a dance, since a cleaner and simpler definition can swing people's opinion about inclusion/exclusion, so the influence goes both ways.
Okay, what about the Earth? If mitochondria are alive, you must also consider the Earth as being alive too. Personally, I think it's a simple answer. Here's my positively b reasoning on the topic for anyone daring enough. It can be a very blurred line, but much of that is our shadow. Mitichondria are more alive than they are dead. Simply because they exist as potential and can go on and are intended for this, for lack of better words. Where as a rock will not come alive, no matter the conditions. We hope.
Maybe we should think of it like we do for other forms of energy and how I be thought we did think of it already but was of biochemical energy expressions. Along with kinetic energy, potential energy, chemical energy. Surely there is a number determined for the maximum lifetime energy output potential (work) of a single mitochondrion. While it is plain and simple, that's just life for you
Okay, what about the Earth? If mitochondria are alive, you must also consider the Earth as being alive too. Personally, I think it's a simple answer. Here's my reasoning on the topic for anyone daring enough. It can be a very blurred line, but much of that is our shadow. Mitichondria are more alive than they are dead. Simply because they exist as potential and can go on and are intended for this, for lack of better words. Where as a rock will not come alive, no matter the conditions. We hope.
Maybe we should think of it like we do for other forms of energy and how I be thought we did think of it already as biochemical energy expressions. Along with kinetic energy, potential energy, chemical energy. Surely there is a number determined for the maximum lifetime energy output potential (work) of a single mitochondrion. While it is plain and simple, that's just life for you.
"Molecular biologists tend to focus on characteristics like metabolism, growth and development, response to stimuli, reproduction, and the ability to process information or evolve."
Even if you stretch the others real hard, I don't see how you'd argue that the Earth "reproduces." Especially not the more rigorous definition of reproduces fertile copies of itself which can evolve.
On an ecosystem (not geological) level, one could argue that space colonization is reproduction and that spaceships are the ecosystem's spores.
Wake me up the day we find a new earth, a baby earth right by us and the moon...
> If we think of mitochondria as non-living organelles, how will we ever harness their full potential?
"Alive" is a fuzzy boundary in concept space that helps humans navigate a fractally complex world. It's not a fact about mitochondria that either hides or reveals structure. We can harness the potential of viruses, and reasonable people can disagree on whether they are alive.
> Mitochondrial DNA mutates 100-1,000 times faster than the human genome
This statement is very interesting for two reasons:
1) We not consider mitochondrial DNA as part of the human genome when it's clearly is and can be used to establish the maternal genetic lineage.
2) Traditionally, we always think of telomere reduction and genetic mutations as the root cause of aging but not mitochondrial genetic damages.
> 2) Traditionally, we always think of telomere reduction and genetic mutations as the root cause of aging but not mitochondrial genetic damages.
A lot of research is looking into the role of mitochondrial damage as causes for a number of conditions.
> If one considers bacteria as living entities — and all biologists seem to — then it is impossible to explain why mitochondria are not.
There seems to be a strange, half-hubris, half-pride vein that runs through Humanity that would see us as lesser for being hosts to benevolent bacteria, despite us very obviously being unable to survive without benevolent bacteria.
I think it just attacks the wholeness of ‘self’ and starts to reveal the true complexity of nature.
We didn't evolve to understand "self", and indeed most animals do not. There was no evolutionary pressure to do so. We're having to discover it piece by piece.
We aren't driven solely by evolutionary pressure. We can (and have) developed cultures that can easily accept that humans are "just" part of a larger system, even having a unique role, without having to be superior. Our culture isn't like that, of course. We are obviously doing a good job of being "in charge" of the planet and definitely not charging headfirst into a mass extinction event with our collective eyes closed.
We had evolutionary pressure to evolve self-preservation, and that stars with self, doesn't it?
Unable to survive without them is pushing it. When one takes strong antibiotics most of them die.
Everyone knows we're already that. The importance of gut microbiome for one - cited loads.
Wonerful! This article is a mind-meld of Humberto Maturana’s work on autopoiesis with almost any of Nick Lane’s deep discussions of bioenergetics e.g., the wonderful book “ Power, Sex and Suicide: Mitochonria and the Meaning of Life” or his equally strong book “Transformer: The Deep Chemistry of Life and Death” that is focused on the Kreb’s cycle. He brings biochemistry and bioenergetics alive in a way that will impact your thinking.
Maturana and Valera gave a brilliant definition of “living” in Autopoiesis and Cognition: The Realization of the Living” (1980). But their writing style will make this a tough read. Terry Winograd write a useful summary if Maturana’s philosophy in his computer science classic “Computers and Cognition”.
> My heart can exist independently of me, and be transplanted into other people, but does it mean that it is alive?
Interesting analogy, made more interesting still if one replaces "heart" with "brain."
And what if you reverse mitochondria and host cell? If you remove the mitochondria, is the host cell still alive? The analogy would be to remove the heart from its 'host' environment, and asking if the remaining body still can be called alive.
"for a man cut open is, so far, not a man. And if you do not sew him up speedily you will not see organs, but death."
Today I learned that mitochondria are the only organelles that replicate “on their own” inside a cell, while the other organelles just bud off the preexisting ones. I wonder how they are signaled to do so though.
Reminds me of sea slugs that eat plants and then integrate their chloroplasts to produce energy, or my dad who kept swapping the same Honda motor through all our go karts because it was too good to get rid of.
I'll add the following to the conversation :
https://x.com/niko_kukushkin/status/1854593093636350387 and https://web.archive.org/web/20170506064530/https://inference...
If you want a fun scifi horror novel to read related to this topic, check out Parasite Eve by Hideaki Sena. It's the novel that inspired the PSX game. The whole plot revolves around mitochondria and was inspired by the author's time as a grad student. I read it a few months ago and really enjoyed it.
Consider that there are thousands of mitochondria (MT) in an individual muscle cell. Cell diagrams often make it look like there is one MT organelle. It's highly misleading.
Single cell bacteria have thousands of genes. MT have a few dozen genes. Many of the genes that regulate MT are contained in the cell's nucleus.
As a layman I'm kind of baffled by the enduring pop-sci interest in mitochondria.
To me the far more interesting organelle is the ribosome. This elegant self-replicating machine that is highly conserved across lifeforms is fascinating and much closer to the origin of life than mitochondria.
How did ribosomes evolve? Are the ribosomes that we see in modern organisms the first design that did evolve? Why are they highly conserved?
Are ribosomes alive as well?
The mitochondria and their dysfunction are likely the basis of most aspects of aging, so an intensive interest in them is understandable.
Also thought to be involved with Chronic Fatigue Syndrome (CFS/ME).
That's a debatable statement and it doesn't explain the public appeal of mitochondria over ribosomes that predates recent research on the relationship between mitochondria and aging.
Why are you insisting on this comparison to ribosomes? They’re both interesting.
I'm just wondering why we always see pop-sci mitochondria content but no ribosome videos.
I think it's the catchy nickname "powerhouse of the cell."
Ribosomes don't have a catch nickname so they get a lot less content produced about them.
If I was a highschool biology teacher I'd probably call them "The assembly line of life." That would stick in people's minds I bet.
Then go ahead. Make those videos. Sell that vision. There's no one stopping you except you.
I don't get the adversarial tone about this.
My intention in asking the question isn't to create animosity. I'm just curious why the thing that I've observed is a thing.
Because bringing up “what about Y?” When the discussion topic is X and there is no connection to Y goes against HN norms.
But there is a connection between the X and Y in this case.
One is a subset of the other. We're talking about the same thing man, I'm just making the point that I feel that there should be greater emphasis on the subset.
Look at the top thread in this post, people are doing a very similar thing.
I truly think that the pop-sci interest in mitochondria stems from the nickname and for no other reason and to me that's a very interesting thing.
Ribosomes and mitochondria are not the same thing.
Agreed. Ribosomes are a subset of mitochondria.
Neither one is a subset of the other. I think you are very confused about your microbiology. I'm not going to continue this conversation.
https://en.wikipedia.org/wiki/Mitochondrial_ribosome
All organelles are valid. This is not a competition. Both mitochondria and ribosomes are cool in different ways.
It's interesting, could you expand on thus?
It's actually a collection of theories known as the mitochondrial theory of aging: https://en.wikipedia.org/wiki/Mitochondrial_theory_of_ageing
It's a little confusing to look into, because there's a bunch of separate theories about the nature of aging that all involve mitochondria in some way. You will find news articles saying that the mitochondrial theory of aging was discredited because of some study done, but when you look into it, it turns out that what was shown was that some specific variant of the theory was insufficient for accounting for all forms of aging, which is not the same thing. Each mitochondrial theory of aging is a theory about one pathway by which mitochondrial function or dysfunction results in aging damage, the reality is that many or all of these theories are true and aging is the aggregation of damage from all of them, and more pathways we have yet to discover.
Generally speaking, the vast majority of aging damage comes, directly or indirectly, from the accumulating damage from healthy operation of mitochondria over long periods of time, or the accumulation of cells with unhealthy mitochondria that produce damage more rapidly. The ELI5 is that mitochondria produce free radicals, free radicals chemically alter basically anything they touch, and aging is simply the slow accumulation of intercellular and intracellular damage, and if you follow the history of these molecules back to when they diverged from being in a healthy state, it is almost always the result of oxidative damage (e.g. free radicals of the sort produced by mitochondria).
Another ELI5 way of looking at it: you may not know this, but mitochondria only live a couple of days. They are constantly being refreshed in your cells because of the severe oxidative stress they undergo. They also sometimes break or leak, letting those reactive oxygen species into the cell and causing damage. Aging is the accumulation of this damage.
But I said aging was "downstream of" mitochondrial dysfunction. That's because not all aspects of aging is due to reactive oxygen species leaking out like I seemed to claim above. That's just one example. There are cells in your body that have lost all mitochondria, often due to a freak genetic mutation in the mitochondrial DNA of that cell. Surprisingly these cells don't die, but rather switch into a mode of operation where they slow down and live off energy extracted from the intercellular medium and converted into ATP by various molecular systems embedded in the cell membrane. These processes, as it turns out, free radicals out of the cell during operation, spewing reactive species into the body. This ends up being responsible for hardening tissue, lack of energy, and many other symptoms of aging. But the root cause? The mitochondria stopped working in that cell, so still a mitochondrial issue.
Or, the aging of heart cells and the hardening of arteries is largely due to the collection of dysfunctional lysosomes that are full of garbage they are unable to break down. These clutter cells, harm their efficiency, and eventually have enough collective effect as to make the tissue as a whole less viable. Leading to heart attacks and other cardiovascular disease, which is the leading cause of age-related death alongside cancer. Want to guess what these defective lysosomes are full of? Mostly undigested mitochondria, specifically the highly damaged structures of mitochondria that suffered too much oxidative damage from long operation.
Oh, and what about cancer? Well cancer needs A LOT of energy to keep replicating, and so it should be no surprise that many of the mutations among common cancers have to do with genes in the nucleus affecting mitochondrial function, or the various signaling pathways between the nucleus and the mitochondria of the cell. This article covers some of the ways that cancer uses mitochondria: https://pmc.ncbi.nlm.nih.gov/articles/PMC4371788/
The best lay introduction I know is "Ending Aging" by Aubrey de Grey and Michael Rae. The book is meant to be an enumeration of all the things that need to be done to biologically reverse aging, but ends up being more than 80% about mitochondria and mitochondrial dysfunction, because of its out-of-proportion impact on the aging process.
Ribosomes are much smaller than mitochondria. Moreover, mitochondria have a lot of ribosomes inside that they use to make their own proteins. https://en.wikipedia.org/wiki/Mitochondrial_ribosome
> Are ribosomes alive as well?
Nah [1]. They do single task. They just read RNA, pick amino acids [1] and make proteins. If a cell were your house, it's like a 3D printer.
Mitochondria are much bigger, they have their own DNA, they reproduce, have a lot of internal structure, they do all the task of a normal cell. If a cell were your house, it's like having a bunch of squirrels trained to wind the clocks in exchange for peanuts.
[1] The definition of alive is complicated, so I prefer a "Nah" instead of a super hard "No".
[2] There are some details I'm hiding, like mRNA, tRNA and even rRNA.
Todays ribosomes are not alive by any definition.
But it's possbile they are descendants of some self-replicating self-catalyzed RNA chain (RNA world)
They are both very interesting. I don’t think there’s necessarily interest in one are the expense of another?
Mitochondrial health is considered a strong proxy for overall health.
I'd been taught mitochondria maybe came from bacteria back in high school 40 years ago but I didn't realise till now that Lynn Margulis also proposed the cell nucleus arose in a similar way.
(paper https://pmc.ncbi.nlm.nih.gov/articles/PMC34369/)
“In the early 20th century, Albert Einstein and Claude Shannon laid out the three pillars of the physical world: matter, information, and energy.”
I’ve yet to see a convincing argument that information has independent existence. The notion is ontologically absurd on its face.
I agree completely with all the points made in the article and would double down on the critique of the philosophy of biology as a discipline and science itself: namely that is has historically evolved as a mere system of typologies and that this is so settled in and so sacrosanct that biology is such a superstition with human-made categories a couple hundred years ago and not a real science.
We see the exact same things also when discussing what is a species and also completely disregarding the reality of horizontal gene transfers etc in the strict, traditional trees.
The models are quite wrong and even reduced wrong.
There is this one famous article that shows how traditional biology would go and analyze a transistor radio, namely just label its assumed components!
Here is the discussion: https://news.ycombinator.com/item?id=31697757
I thought the Mitochondria Liberation Front was defunct. Are people getting back into this type of linguistic debate? Anyway, uplifting as a whole is pretty sketchy and I'm not sure there's too much point.
I once asked a biologist “using today’s understanding, what is life?” She answered with ”the more we learn, the more I ask myself what is biology?”
Feels analogous to the CPU and the Management Engine heh.
For a fictional macro version of the Margulis hypothesis, I'd recommend 'Alien Clay' by Adrian Tchaikovsky
Interesting argument
> control bioenergetics across the eukaryotic tree of life.
What types of outcomes do we unlock when we can control bioenergetics?
unlimited power
"In the early 19th century, "
With that level of proofreading, I'm not sure what else was wrong in the article...
It reminds me the game Parasite Eve.
Most of the Japanese games/media foreshadow/hint you about actual or potential facts written in papers but not understandable to teenagers until theẏ grow up.
I don't know why this is being downvoted. It's quite apropos for being a piece of fiction toying with this very concept.
It is a videogame based on/continuing a cheesy scifi novel that played with the concept of mitochondria being alive (also sentient). Sure it's not quite scientifically sound, but it still explains the concept with enough actual facts (very easy to distinguish from the fictional ones), and the ludicrous nature of it all makes it so you won't *ever* forget that mitochondria are in fact a part of the cell and their normal function is being involved in energy production.
I can warrant 90% of people who ever thought about the mitochondrion's existence and function (beyond basic school formation) that aren't working or studying in related fields are just people who played this game. I can bet there's a non-zero amount of scientists that got into this stuff because they played the game as kids or teens.
Surely I can't be the only one who read this as midichlorians and thought it was something to do with star wars. Actually feel a little ashamed about that.
Pointless word games.
the mitochondria are alive, and they're doing just fine
Is this a blog post or... Why does this have 305 comments?
Talking about what is considered "alive" is an interesting exercise, and shows just how fuzzy those boundaries can be sometimes. But I really don't see how this has any practical impact on how we study mitochondria.
> If we think of mitochondria as non-living organelles, how will we ever harness their full potential?
Whenever anyone uses the "harnessing [its] full potential" cliché, my bullshit alarm starts buzzing. I don't think this article is bullshit, but...we can "harness" as much "potential" as mitochondria have whether we consider them alive or not.
So what now? We give them rights?
Or deport them.
I expect such lively news to make this comment section the powerhouse of the front page. :^)
It's funny that this phrase has had such staying strength, while the key word in it, "powerhouse," has fallen out of fashion. The more modern American English way to phrase it would be "the power plant of the cell."
Anecdotally, I feel like I've heard "powerhouse" used somewhat regularly when describing impressive people, i.e.: "Such-and-such is an absolute powerhouse on the field", or "That person is so productive, they're a powerhouse".
So maybe the original usage has been subsumed by "power plant", but I think the word has alternative meanings which persist.
It kind of just shifted distinctions.
Powerhouse is a common way to describe an athlete, a high performance engine, or a very strong stock buy -- it has just moved away from the infrastructural uses.
That's an interesting thought, I haven't picked up on it but you're right. Most of my associations with powerhouse are from trails or ares that used to have powerhouses and now have empty buildings, ruins or traces left over. I do think about powerhouses in the context of dams but that is likely leftover from an earlier time.
I’m pretty sure people still talk about powerhouses of hydroelectric dams
Can you describe the distinction?
Distinction: I am a millennial, and actually had to go look up just now what a "powerhouse" is. I am familiar with the term in its metaphorical sense, but was heretofore unacquainted with the literal definition. "Power plant" or "power station" would, yes, be more immediately understood by my generation. The phrase "Mitochondria is the powerhouse of the cell" would read to modern children like saying "The mitochondrion is the rock star of the cell."
These things do happen. I was in my 30s before I learned what the "firewall" of a car was...
I'm sure there's a fantastic midi-chlorian joke here.
If we label mitochondria as alive, that would mean prison laborers must count as living, too.
> thinly veiled abortion argument
Kek.
Sir/Ma'am, I live in America. What is reasonable and compassionate and sensible is simply beyond the grasp of most everyone, looks to me.
I wonder what mitochondria dream about. Do they have elections? Politics? Their own understanding of the universe, that somehow ends on the skin surface?
Alive != sentient
debatable
even "dead=!sentient" remains debatable
> I wonder what mitochondria dream about.
ATP sheep.
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