So why are us southpaws a rarity? The article and the linked research paper both point to bipedalism and bigger brains as the cause, and the paper vaguely seems to hint at selective pressures leading to the right hand getting favoured by the majority of the population, but why?
The question from the headline is excellent, if only it was actually answered.
Here's my five minute lunchtime hypothesis: it's because the heart is on the left. As human behavior demanded increasing precision from the hands, being a little farther from the heartbeat was a slight advantage.
Wikipedia on Situs Inversus (visceral organs are mirrored, heart on the right, liver on left) [0], mentions mixed results regarding handedness. There would be a load of other confounding factors here and I know nothing about medicine.
Situs inversus ("dextrocardia") is a rare disorder. What I postulated is a (very) small selective advantage leading to a neurological mechanism evolving over generations, not a direct line from the heart to handedness during development. Anyway, the effect would be very slight, and even if it did exist, it could have gone away later, but dexterity would have been baked in at that point (see also the ocular blind spot).
Here’s my multiple years of anatomy classes response: the heart isn’t on the left. The aorta is, sure, but the vena cava is on the right. Also people with situs inversus (essentially all organs flipped laterally from
“normal”) aren’t obviously more prone to left-handedness.
> Also people with situs inversus (essentially all organs flipped laterally from “normal”) aren’t obviously more prone to left-handedness.
I feel like this isn’t really an argument against the theory. If right handedness did evolve because of heart position, a later genetic mutation to have the heart on the opposite side wouldn’t suddenly undo the previous evolution towards right handedness.
It might be hard to eliminate confounding factors depending on when the research was done. A lot of people in my generation were still dissuaded pretty heavily from writing with their left hands. I'm not entirely convinced anymore as a lay person that "handedness" is a real, distinct phenomenon that's primarily genetically determined or a result of the organization of the brain. It's equally possible that it's a learned preference and that the way the brain organizes around it is as a result of the preference's impact on how you have to solve problems with your preferred hand in a society that preferences right-handedness.
Not disagreeing that handedness is probably unrelated to heart position.
But why would situs inversus somehow be tied to this at all? If there's a gene that favors right-handedness, it's not like it would somehow "choose" left-handedness because the individual has their internal organs flipped.
not only smaller but having 2 lobes rather than 3, the left lung is possessed of a featureknown as the cardiac "notch" an involution of the lobe that corresponds to the larger left ventricle of the heart.
The heart is asymmetrical, but it’s in roughly the center of the chest. The left auricle and ventricle are larger muscles because they’re pumping through the descending aorta to the extremities, that’s the systemic circulatory branch, the plumbing for which is also largely to the right, while the right are pumping into the lungs alone as part of the pulmonary circulatory branch. The left lung (right on those with situs inversus) has two lobes and basically accommodates the extra muscle mass on its side of the heart, but if you really want to kill someone you stab them through the sternum, kind of dead center, not where they hold their hand when performing patriotism.
even this is wrong, a penetrating weapon aimed for the heart is applied below the sternum at roughly the positionof the 3rd shirt button, and thrust upward at shallow angle topass behind the manubrium, and is then levered into a pommel upward position so as to lacerate the heart
I wonder why you're getting downvoted? Even if it turns out you're completely wrong it's still an interesting point and something I never even considered before.
Sometimes I think people downvote me because they're frustrated that I didn't engage further. After twenty years of Internet discussions, I'm a little burned out and I tend to fire and forget.
I am curious at what age hand preference develops. And can you exert any influence on that development?
In particular, I would expect the influences to be somewhat counter intuitive. With things like having to use the left hand to hold a caregiver's hand in early walking preferencing the right for accessory use. At infant ages, it would be neat to see if preference of holding a baby on a side influences things.
I would be interested in studies into impact of left hemisphere importantce on the right hand usage, possibly the more sophisticated and "logical" usage of our hands pressured it as well.
It's true that the creative vs. logical side of the brain is mostly a myth.
But the hemispheres absolutely DO specialize in very predictable ways. Core language faculties are almost always handled by the left hemisphere, for instance.
Face processing is almost universally handled by the right hemisphere.
We know these things from people who have suffered an injury to one of their hemispheres. A person with damage to the right hemisphere has a chance of not being able to recognize faces, but that's almost never seen in an injury that exclusively effects the left-hemisphere.
Thanks! Although I understand there is still some specialization in each of the hempispheres, which could influence it, but I probably went too strong with my imagination here.
Left-handed people are often excluded from participating in MRI studies. To my personal dismay, as these studies often paid 25 euros per hour ~20 years ago, a significant sum for my student self that I could not partake in. It has however given me significant doubts about any strong lateralization claims...
What does it say for mixed-handed folks like myself (different skillsets per hand - in other words, throw and write with different hands)? What about cross-dominance (different body parts differ on dominant side - in other words, a right-handed person being left-foot dominant)?
I've been told that it's effectively a mental illness if discovered during childhood (as is ambidexterity). Yet I can't help but think that it is not a mental illness, but rather something else.
> I've been told that it's effectively a mental illness if discovered during childhood (as is ambidexterity). Yet I can't help but think that it is not a mental illness, but rather something else.
https://en.wikipedia.org/wiki/Handedness#Types: “Mixed-handedness or cross-dominance is the change of hand preference between different tasks. This is about as widespread as left-handedness.”
⇒ about 20% of the population is not strictly right-handed. That’s not a majority, but I think the word to use for that is “normal”.
In order to present it as a mental illness there would have to be some kind of negative effect, wouldn't there? These differences you mention don't stand out as harmful or even disadvantageous.
I'm sorta here too. I'm right handed, no external pressure to use one hand or the other in early age. Mother is a lefty, father is a righty. As a result I often used the computer mouse on either side as a kid, really wherever it was left by the last user.
Learned to shoot a bow as a kid but only learned as an adult I'm left eye dominant, and to take advantage would require re-learning the bow in my left hand(many many strikes on my arm sent be back to a righty). Shooting guns is a similar situation, but I'm a fairly good shot regardless. It definitely makes using sights weird.
I'm semi-ambidextrous too, with enough focus I can somewhat cleanly write with either hand, and I'm generally good with my hands in fine tasks, with only a minor preference to pick up a tool with my right hand.
I wonder how common this is. People seem surprised when I demonstrate my left handed writing.
I'm otherwise a lefty but I use computer mice right handed, because when I first started using a computer in elementary school all of the computer labs were set up right handed.
FWIW, I'm a righty, but relearned to use a mouse left handed for ergo benefits at my first real job; now I left mouse for work and right mouse for home. I prefer ambidextrous mice anyway, but it's really hard to find a left hand mouse if you want that. Even the ambidextrous mice often have thumb buttons for the right thumb. It's not to hard to learn to use a pointer with either hand; IMHO as someone who can't do a lot of complex motion with my non-dominant hand. I think there's a lot of convenience gained by accepting right mousing, although it is a longer reach if you have a keyboard with stuff to the right of your letters.
My parents generation is maybe a bit older than you, one of my mom's siblings was forced to right handedness. My mom is left handed and says they tried a little with her, but it only took for some things.
Probably because it didn't happen to you, or kindergarteners don't know better and just play along. I only remember it because I was a little shit and got into a big fight about it. It would have been late 80s.
An elementary school teacher of mine had this happen to her (this was in the early '90s, so her experience I'm guessing would have been in the late '60s).
One day she wrote her name twice on the whiteboard and asked us to identify the difference between the two; visually they were identical, but she wrote one with her left hand and one with her right. She said as a kid she was made to use her right hand when she started showing signs of left-hand dominance.
I didn't know what difference it made and there was one left handed scissors so it went to the kid who knew. I'm left eyed and often wonder if I should have learned to write left handed.
it happened to me, and when my parents found out they flipped out.
i found out about my parents reaction like everyone else,, suddenly there was a bunch of screaming profanity and acoustic violence coming from the principals office
Didn't I understood the text or is the 'why' not really part of it? I expected more than a vague 'because it slightly existed and then hands are free to do things and brains got bigger'.
I miss the point.
Drop the "every" part and you can see the word that needs to be agreed with.
"One is supposed to do such and such."
"Everyone is supposed to do such and such."
"They are supposed to do such and such."
"People are supposed to do such and such."
I think that's the case for all the "every <noun>". "Every human is a person", for example. This would make sense, to put it in programming terms - the verb applies to an element in an array of people, not the array itself (which would be plural): for every single human, that human is a person.
> The words everybody and everyone are pronouns that describe a group of people, but grammatically they are singular. The last part of each word is a singular noun: body and one.
So why are us southpaws a rarity? The article and the linked research paper both point to bipedalism and bigger brains as the cause, and the paper vaguely seems to hint at selective pressures leading to the right hand getting favoured by the majority of the population, but why?
The question from the headline is excellent, if only it was actually answered.
I remember reading that there is evidence that Neanderthals tended to be left handed. Someone else might be able to confirm/debunk this.
Here's my five minute lunchtime hypothesis: it's because the heart is on the left. As human behavior demanded increasing precision from the hands, being a little farther from the heartbeat was a slight advantage.
Wikipedia on Situs Inversus (visceral organs are mirrored, heart on the right, liver on left) [0], mentions mixed results regarding handedness. There would be a load of other confounding factors here and I know nothing about medicine.
0 - https://en.wikipedia.org/wiki/Situs_inversus
Childhood handedness development within the brain became independent of organ positioning, after positioning had become established.
Situs inversus ("dextrocardia") is a rare disorder. What I postulated is a (very) small selective advantage leading to a neurological mechanism evolving over generations, not a direct line from the heart to handedness during development. Anyway, the effect would be very slight, and even if it did exist, it could have gone away later, but dexterity would have been baked in at that point (see also the ocular blind spot).
If this was the case wouldn't it be easier to measure the pulse in peoples left wrists? Which doesn't seem to be a thing?
Here’s my multiple years of anatomy classes response: the heart isn’t on the left. The aorta is, sure, but the vena cava is on the right. Also people with situs inversus (essentially all organs flipped laterally from “normal”) aren’t obviously more prone to left-handedness.
> Also people with situs inversus (essentially all organs flipped laterally from “normal”) aren’t obviously more prone to left-handedness.
I feel like this isn’t really an argument against the theory. If right handedness did evolve because of heart position, a later genetic mutation to have the heart on the opposite side wouldn’t suddenly undo the previous evolution towards right handedness.
It might be hard to eliminate confounding factors depending on when the research was done. A lot of people in my generation were still dissuaded pretty heavily from writing with their left hands. I'm not entirely convinced anymore as a lay person that "handedness" is a real, distinct phenomenon that's primarily genetically determined or a result of the organization of the brain. It's equally possible that it's a learned preference and that the way the brain organizes around it is as a result of the preference's impact on how you have to solve problems with your preferred hand in a society that preferences right-handedness.
Not disagreeing that handedness is probably unrelated to heart position.
But why would situs inversus somehow be tied to this at all? If there's a gene that favors right-handedness, it's not like it would somehow "choose" left-handedness because the individual has their internal organs flipped.
>Here’s my multiple years of anatomy classes response: the heart isn’t on the left.
Why is the left lung smaller, then?
not only smaller but having 2 lobes rather than 3, the left lung is possessed of a featureknown as the cardiac "notch" an involution of the lobe that corresponds to the larger left ventricle of the heart.
More piping to and from the heart exists on the left instead of the right?
the Aorta and Vena Cava are muchmore central than sinistral.
the aortic arch begins decent left of the coronary corpus, but becomes centralized, tandem with the Vena Cava.
The heart is asymmetrical, but it’s in roughly the center of the chest. The left auricle and ventricle are larger muscles because they’re pumping through the descending aorta to the extremities, that’s the systemic circulatory branch, the plumbing for which is also largely to the right, while the right are pumping into the lungs alone as part of the pulmonary circulatory branch. The left lung (right on those with situs inversus) has two lobes and basically accommodates the extra muscle mass on its side of the heart, but if you really want to kill someone you stab them through the sternum, kind of dead center, not where they hold their hand when performing patriotism.
>if you really want to kill someone you stab them through the sternum, kind of dead center, not where they hold their hand when performing patriotism.
Noted, thanks.
even this is wrong, a penetrating weapon aimed for the heart is applied below the sternum at roughly the positionof the 3rd shirt button, and thrust upward at shallow angle topass behind the manubrium, and is then levered into a pommel upward position so as to lacerate the heart
I wonder why you're getting downvoted? Even if it turns out you're completely wrong it's still an interesting point and something I never even considered before.
Sometimes I think people downvote me because they're frustrated that I didn't engage further. After twenty years of Internet discussions, I'm a little burned out and I tend to fire and forget.
I am curious at what age hand preference develops. And can you exert any influence on that development?
In particular, I would expect the influences to be somewhat counter intuitive. With things like having to use the left hand to hold a caregiver's hand in early walking preferencing the right for accessory use. At infant ages, it would be neat to see if preference of holding a baby on a side influences things.
I would be interested in studies into impact of left hemisphere importantce on the right hand usage, possibly the more sophisticated and "logical" usage of our hands pressured it as well.
One of many articles out there debunking the pop-psych mythology around brain lateralization: https://themindcompany.com/blog/left-brain-right-brain-myth
It's true that the creative vs. logical side of the brain is mostly a myth.
But the hemispheres absolutely DO specialize in very predictable ways. Core language faculties are almost always handled by the left hemisphere, for instance.
Face processing is almost universally handled by the right hemisphere.
We know these things from people who have suffered an injury to one of their hemispheres. A person with damage to the right hemisphere has a chance of not being able to recognize faces, but that's almost never seen in an injury that exclusively effects the left-hemisphere.
Thanks! Although I understand there is still some specialization in each of the hempispheres, which could influence it, but I probably went too strong with my imagination here.
Left-handed people are often excluded from participating in MRI studies. To my personal dismay, as these studies often paid 25 euros per hour ~20 years ago, a significant sum for my student self that I could not partake in. It has however given me significant doubts about any strong lateralization claims...
What does it say for mixed-handed folks like myself (different skillsets per hand - in other words, throw and write with different hands)? What about cross-dominance (different body parts differ on dominant side - in other words, a right-handed person being left-foot dominant)?
I've been told that it's effectively a mental illness if discovered during childhood (as is ambidexterity). Yet I can't help but think that it is not a mental illness, but rather something else.
> I've been told that it's effectively a mental illness if discovered during childhood (as is ambidexterity). Yet I can't help but think that it is not a mental illness, but rather something else.
https://en.wikipedia.org/wiki/Handedness#Types: “Mixed-handedness or cross-dominance is the change of hand preference between different tasks. This is about as widespread as left-handedness.”
⇒ about 20% of the population is not strictly right-handed. That’s not a majority, but I think the word to use for that is “normal”.
In order to present it as a mental illness there would have to be some kind of negative effect, wouldn't there? These differences you mention don't stand out as harmful or even disadvantageous.
I'm sorta here too. I'm right handed, no external pressure to use one hand or the other in early age. Mother is a lefty, father is a righty. As a result I often used the computer mouse on either side as a kid, really wherever it was left by the last user.
Learned to shoot a bow as a kid but only learned as an adult I'm left eye dominant, and to take advantage would require re-learning the bow in my left hand(many many strikes on my arm sent be back to a righty). Shooting guns is a similar situation, but I'm a fairly good shot regardless. It definitely makes using sights weird.
I'm semi-ambidextrous too, with enough focus I can somewhat cleanly write with either hand, and I'm generally good with my hands in fine tasks, with only a minor preference to pick up a tool with my right hand.
I wonder how common this is. People seem surprised when I demonstrate my left handed writing.
Left-footed and right-handed. I find my "handedness" follows where the activity is driven from (upper/lower body).
Soccer, snowboarding, batting, golfing: lefty
Writing, throwing, tennis, pool: righty
"Left-footed and right-handed"
Same as Mickey Dolenz who drummed for the Monkees. Very unusual combination.
You were probably a left-handed person who was taught to write/use tools with their right hand in kindergarten. I got this treatment too.
I'm otherwise a lefty but I use computer mice right handed, because when I first started using a computer in elementary school all of the computer labs were set up right handed.
FWIW, I'm a righty, but relearned to use a mouse left handed for ergo benefits at my first real job; now I left mouse for work and right mouse for home. I prefer ambidextrous mice anyway, but it's really hard to find a left hand mouse if you want that. Even the ambidextrous mice often have thumb buttons for the right thumb. It's not to hard to learn to use a pointer with either hand; IMHO as someone who can't do a lot of complex motion with my non-dominant hand. I think there's a lot of convenience gained by accepting right mousing, although it is a longer reach if you have a keyboard with stuff to the right of your letters.
When was that? I know it used to happen, but I haven't heard of or seen that in my lifetime, I'm nearly 60.
My parents generation is maybe a bit older than you, one of my mom's siblings was forced to right handedness. My mom is left handed and says they tried a little with her, but it only took for some things.
Probably because it didn't happen to you, or kindergarteners don't know better and just play along. I only remember it because I was a little shit and got into a big fight about it. It would have been late 80s.
An elementary school teacher of mine had this happen to her (this was in the early '90s, so her experience I'm guessing would have been in the late '60s).
One day she wrote her name twice on the whiteboard and asked us to identify the difference between the two; visually they were identical, but she wrote one with her left hand and one with her right. She said as a kid she was made to use her right hand when she started showing signs of left-hand dominance.
I didn't know what difference it made and there was one left handed scissors so it went to the kid who knew. I'm left eyed and often wonder if I should have learned to write left handed.
it happened to me, and when my parents found out they flipped out.
i found out about my parents reaction like everyone else,, suddenly there was a bunch of screaming profanity and acoustic violence coming from the principals office
Didn't I understood the text or is the 'why' not really part of it? I expected more than a vague 'because it slightly existed and then hands are free to do things and brains got bigger'. I miss the point.
Actual study here: https://journals.plos.org/plosbiology/article?id=10.1371/jou...
My take is that when they added extra factors to the Bayesian model, the plot was such that humans were no longer outliers.
Whether or not that's scientifically rigorous, or even interesting, I leave to others to determine.
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'Everyone' is treated as singular (aside from 'everyone are' sounding completely wrong).
Drop the "every" part and you can see the word that needs to be agreed with.
This also applies with "some" https://en.wikipedia.org/wiki/Quantifier_(linguistics)Part of the confusion may be that "everyone" is a single word while the example sentence in the Wikipedia article has a non-compound example.
The quantifier does not change the grammatical number of the subject.I think that's the case for all the "every <noun>". "Every human is a person", for example. This would make sense, to put it in programming terms - the verb applies to an element in an array of people, not the array itself (which would be plural): for every single human, that human is a person.
Confidently incorrect.
No, grammatically "everyone" is an indefinite pronoun. a single collective unit.
Is that a British thing? Nobody in North America uses "everyone are"
https://www.britannica.com/dictionary/eb/qa/Everybody-Has-or...
> The words everybody and everyone are pronouns that describe a group of people, but grammatically they are singular. The last part of each word is a singular noun: body and one.
https://en.wikipedia.org/wiki/Encyclopædia_Britannica
> Though published in the United States since 1901, the Britannica has for the most part maintained British English spelling.
It's not.