Why is almost everyone right-handed? A new study connects it to bipedalism

An interesting anecdote that comes to mind is playing old computer games with arrow keys, which used my right hand. I got pretty proficient with this.

Over the years, I (and I imagine many others) switched over to WASD to play newer games with mouse + keyboard, but this meant using the left hand for "arrow keys"

Now I can directly compare how proficient I am with WASD vs Arrow Keys and the result surprised me. I was way worse with arrow keys (right hand) even though back when WASD was becoming a thing I'd rebind WASD to arrow keys because it felt too weird! I would've never imagined back then that WASD could ever feel as natural as arrow keys.

Makes me wonder how much of handedness is truly innate vs learned.

The article didn't really help me understand what it was about bipedalism that resulted in a right handed preference. Also in my family left hand dominates, we are a cluster of left handed people. My theory is if any child wants help with fine motor control the help is provided by a left hand to a left hand.

I always faced left when riding a skateboard back in the day, otherwise known in skater parlance as being "goofy-footed". Facing right felt as difficult as writing with my left hand. I always wondered whether that was just the way I first rode a skateboard and it stuck, but if that was the case, I would expect the distribution of which skateboarders face which way to be about even. But goofy-footed riders are in the minority. I'm right-handed as well. I wonder what's up with that.

Fun little nugget, Australian Sulphur Crested Cockatoos almost universally favour their left feet as a holdfast. They're also left eye dominant.

Here is a funny thing.

I can walk a bicycle perfectly just by holding nothing but the saddle with my right hand. I can pick some spot on the ground ahead, call it, and hit it with the front wheel accurately.

Switch to my left hand and the bike's front wheel starts having a mind of its own.

"No, don't veer that way, Bike; you're not reading my mind, like you do through my right hand!!!"

Why is there handedness on stringed instruments? If you're right handed, you strum a guitar with your right hand, fret with the left. But both are fine motor skills requiring coordination. Left handed players go out of their way to acommodate doing it the other way around; either finding left-handed instruments (challenge: most things they might like/want are not available in lefty version) or suffer with a flipped right handed instrument (control positions on electrics are wrong, asymmetric cutaways for reach are wrong, nuts are slotted wrong for a mirrored string order).

My first thought was, "language". The Broca's area is on the left side of the brain, which is the center of control for logic, language and the right hand. It makes sense to me that an evolutionary feedback loop would develop between the hands and complex language development. So it's not odd that the average human brain would develop -somewhat better control over the right hand than the left.

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 almost never see people using a left hand mouse these days.

As younger people start using computers they generally will learn with right-handed mice and will thus develop those fine motor skills in that hand. I wonder if this will make right-handedness even more dominant.

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.

"Handedness" is two traits, not one. The paper finds bipedalism explains strength (how strongly someone prefers a hand); brain size explains direction (which one). Most coverage conflates them.

Australopithecus was already strongly lateralized — committed handers — long before the rightward consensus emerged. Two traits, evolved separately by millions of years.

>Humans sat conspicuously outside the pattern that explained every other primate, but ... once you account for upright walking and a large brain, humans stop looking like an evolutionary anomaly.

>Using the same models, the team was also able to estimate likely handedness in extinct human ancestors. The picture that emerges is a gradient [from less handedness to more as time goes on]

"we explored the data until we found a statistical anomaly and it implies X" may be interesting[1], but there are TONS of those that are NOT true. is there supporting evidence for this, or is it just "hey this math says maybe"? it sounds more like the latter (as it quite literally seems like they're claiming roughly "big arm + big brain = big handedness", both in this site and in the paper itself), in which case they might also be interested in this study that pirates keep the global temperature down: https://www.forbes.com/sites/erikaandersen/2012/03/23/true-f...

1: from skimming the methodology in the paper, I honestly think this may be a fair characterization. it sounds like they combined data columns until one combo came up as P>0.95 and didn't have counter-evidence and said "that means it's probably true". but also some (all?) of that data may have been generated by models they created based on real ape data (I think?), which just sounds even more sus.

I taught English in China 20 years ago. Of the thousands of students I taught, none wrote with their left hand.

"There are no left-handed in China" might sound as ridiculous as "There are no gays in Uganda".

However of those thousands of students, none had messy hand writing. In any class in Europe or the US, around 10% of students have messy writing. Suspiciously equivalent to the supposed number of left-handed students.

I wish they'd look into footedness as well and if there is some kind of correlation. Like orthodox vs southpaw in combat sports, goofy vs regular in skateboard, or just simply left vs right in football (soccer)

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.

I am right handed but left handed for some very specific things such as playing pool or hockey

It is a very bad choice of words to say that "bipedalism" is a cause for hand specialization.

For hands, it is completely irrelevant how many legs a human has, regardless if a human had used 2, 4, 8, 14 or any other number of legs for walking, the hands would have become specialized.

The reason why the hands acquired specialized roles was that they were no longer used for locomotion, i.e. for brachiation in the trees, like in orangutans or gibbons, but their purpose became holding, controlling and moving various objects from the environment.

It is wrong to say that bipedalism has freed the hands to be used for other activities than locomotion, because the causality was reverse, locomotion became restricted to the hind legs, because the hands were used for other activities, like throwing sticks and stones, so they were no longer available for locomotion.

The strong specialization of the 2 hands has appeared because in most cases when something is transformed with the hands, e.g. bones are broken to get the marrow or stones are knapped to get a cutting edge, one hand must be used to fix in place the object that is processed, while the other hand must move against it, normally with some tool.

For the former role, the left hand became specialized, while for the latter role, the right hand became specialized.

Similar specialization is also seen at other animals where a pair of legs is no longer used for locomotion, but it is used for manipulation, for instance at crabs and lobsters.

So there is no doubt that the specialization of the hands was a necessity when they stopped being used for locomotion. However, it is not known why the right hand became the moving hand and the left hand became the holding hand, and not vice-versa. It could have been a random event or it could have been related to the asymmetry in the locations of the unpaired internal organs, like heart, liver, stomach and so on.

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.

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.

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The ‘study’ is fluff.

Paraphrase: Amongst primates there is a correlation between brain size and bipedalism with handedness… (unless you exclude humans, in which case there isn’t.)

That’s like saying: “Alongst animals there is a correlation between height and neck length… unless you exclude giraffes, in which case there isn’t.”

If a correlation disappears when you remove one datapoint, then the correlation was not really a broad pattern across the dataset. It was mostly a story about that one datapoint.

I mean, I get it… you gotta publish something. But, geesh… this is beyond stupid.