to get an ECG which is one of several strategies they could use. (e.g. lately I've been interested in Heart Rate Variability which has gotten me looking at reading heart rate with cameras, radars, pressure gauges, ultrasound, etc.)
"Analysis of the data suggests that a blue whale’s heart is already working at its limit, which may explain why blue whales have never evolved to be bigger."
Incredible to think of the volume of all the blood it's pumping around.
I don't understand how that would limit evolution. Bigger bodies can evolve together with bigger hearts, as already witnessed with the very whales being researched.
The volume of blood that needs to be pumped increases e̶x̶p̶o̶n̶e̶n̶t̶i̶a̶l̶l̶y̶ cubically with size, meaning the cells have to do more work, or there have to be more of them. The size of the heart has to match the volume of blood being pumped - if they evolved to be larger, the heart might have to be so big that it creates pathology in other areas, or has to pump so hard it damages tissue, or creates forces so great that veins or arteries collapse or burst.
It's probably not as dramatic an issue as that. It could also be sensory - past a certain size, in order to be sensitive enough to detect damage and deal with normal conditions, it would have to be irritated all the time, or numb to potential hazards.
There are all sorts of second and third order consequences limiting how various vital systems can interplay, so more than likely, it's a combination of a whole bunch of things that subtly limit the overall size to where it's at, and any further increase degrades its abilities to survive.
They're just so huge. Their brains are 4 times larger than a human's brain, but we share a whole lot of structure, from the cellular level to the macro, with two lobes, some shared sulcal features (same folding pattern) which indicates that we likely share enough connectomic structure for the ways in which our brains operate to produce similar conscious experiences. Someday, in the distant future, we should be able to use BCI to feel exactly what it's like to be a blue whale (and vice versa.)
Their brains have similar cortical structure, but even though the brains are about 7 times larger, their cortical surface area is only 2-3 times that of a human. It really puts into context how bizarrely massive our brains are for our relatively tiny size.
For contrast, titanosaur hearts would have been around 500 lbs and up to 6 feet in diameter, and their brains were about the size of a big walnut. These land animals were up to 40m long and 100 tons.
Anyway - physics of tissue and frailties of being made of meat are what keep the whales from getting much bigger.
Cardiac tissue is a surface. Blood is a volume. I think they’re saying blue whale hearts are near the largest current biology can evolve. Which is interesting because it suggests if we could e.g. engineer whales with carbon-fiber hearts or whatever, they’d evolve to grow even bigger.
Blackheart the whale, lurking the oceans, ever devouring and growing. I think you've got a good Lovecraft/Pirates of the Carribean/Black Mirror mashup premise here.
> Looking at the big picture, the researchers think the whale’s heart is performing near its limits. This may help explain why no animal has ever been larger than a blue whale – because the energy needs of a larger body would outpace what the heart can sustain.
I do wonder if those animals have things like valves in their veins, as I understand it if the circulatory system wasn't as complex as it is, heart would have to pump a lot harder to move the volume it does. This isn't an area I know much of anything about, I just know veins have valves and can expand and contract to different stimuli much as a heart can... so even though mammals have one heart it's not like the rest of the system is a static not helping to pump blood.
Note they put a Holter monitor on it
https://www.pnas.org/doi/10.1073/pnas.1914273116
to get an ECG which is one of several strategies they could use. (e.g. lately I've been interested in Heart Rate Variability which has gotten me looking at reading heart rate with cameras, radars, pressure gauges, ultrasound, etc.)
30 BPM at the surface, 4 bpm while diving.
"Analysis of the data suggests that a blue whale’s heart is already working at its limit, which may explain why blue whales have never evolved to be bigger."
Incredible to think of the volume of all the blood it's pumping around.
I don't understand how that would limit evolution. Bigger bodies can evolve together with bigger hearts, as already witnessed with the very whales being researched.
> Bigger bodies can evolve together with bigger hearts, as already witnessed with the very whales being researched.
Hm? Aren't blue whales the biggest animals to ever have lived that we know of?
The volume of blood that needs to be pumped increases e̶x̶p̶o̶n̶e̶n̶t̶i̶a̶l̶l̶y̶ cubically with size, meaning the cells have to do more work, or there have to be more of them. The size of the heart has to match the volume of blood being pumped - if they evolved to be larger, the heart might have to be so big that it creates pathology in other areas, or has to pump so hard it damages tissue, or creates forces so great that veins or arteries collapse or burst.
It's probably not as dramatic an issue as that. It could also be sensory - past a certain size, in order to be sensitive enough to detect damage and deal with normal conditions, it would have to be irritated all the time, or numb to potential hazards.
There are all sorts of second and third order consequences limiting how various vital systems can interplay, so more than likely, it's a combination of a whole bunch of things that subtly limit the overall size to where it's at, and any further increase degrades its abilities to survive.
They're just so huge. Their brains are 4 times larger than a human's brain, but we share a whole lot of structure, from the cellular level to the macro, with two lobes, some shared sulcal features (same folding pattern) which indicates that we likely share enough connectomic structure for the ways in which our brains operate to produce similar conscious experiences. Someday, in the distant future, we should be able to use BCI to feel exactly what it's like to be a blue whale (and vice versa.)
Their brains have similar cortical structure, but even though the brains are about 7 times larger, their cortical surface area is only 2-3 times that of a human. It really puts into context how bizarrely massive our brains are for our relatively tiny size.
For contrast, titanosaur hearts would have been around 500 lbs and up to 6 feet in diameter, and their brains were about the size of a big walnut. These land animals were up to 40m long and 100 tons.
Anyway - physics of tissue and frailties of being made of meat are what keep the whales from getting much bigger.
Nitpick, but the volume increases cubically (it scales with volume), not exponentially.
Thank you, I'll correct that. I was thinking inverse square law, then instead of asking an AI like a good nerd, I just winged it.
> don't understand how that would limit evolution
Cardiac tissue is a surface. Blood is a volume. I think they’re saying blue whale hearts are near the largest current biology can evolve. Which is interesting because it suggests if we could e.g. engineer whales with carbon-fiber hearts or whatever, they’d evolve to grow even bigger.
Blackheart the whale, lurking the oceans, ever devouring and growing. I think you've got a good Lovecraft/Pirates of the Carribean/Black Mirror mashup premise here.
> Looking at the big picture, the researchers think the whale’s heart is performing near its limits. This may help explain why no animal has ever been larger than a blue whale – because the energy needs of a larger body would outpace what the heart can sustain.
Fascinating to learn such details!
Could an animal have several hearts?
yes. I know octopuses and squids have three hearts. Just looked it up and it seems no mammal has more than one heart.
I do wonder if those animals have things like valves in their veins, as I understand it if the circulatory system wasn't as complex as it is, heart would have to pump a lot harder to move the volume it does. This isn't an area I know much of anything about, I just know veins have valves and can expand and contract to different stimuli much as a heart can... so even though mammals have one heart it's not like the rest of the system is a static not helping to pump blood.
Anyone got a direct link to or time index of the recording? I skipped around the video on the linked page but it was all music.
A Whale's tachycardia is my bradycardia. Huh.
There are documented cases of perfectly healthy humans with resting heart rates under 30bpm.
https://www.guinnessworldrecords.com/world-records/lowest-he...