Why are people usually right handed?

as opposed to being left handed? or even ambidextrous? (wouldn’t that make more sense anyway?)

I have a feeling it has something to do with the heart being positioned on the left side of our body and people naturally evolved to be right handed in order to protect that organ. But, that is just pure speculation with no basis at all.

I don’t know why hoomins have handed-ness but cats have it too (I asked my vet). I scrutinized my cat at home and sure enough, he seems to be right-pawed.

I believe the only correct answer to this is that nobody knows. Explanations in terms of other bodily asymmetries, such as the heart, or the “dominant” brain hemisphere being on the left, are, at best, begging the question. Why are the heart and the dominant brain hemisphere normally on the left? We don’t know. But even if we did know, we do not really know whether or how it would influence actual handedness. Some left-handers have their dominant brain hemisphere on the right, but not all by any means.

Possibly it all comes down, ultimately, to the chirality of biological molecules, but we have absolutely no idea why the fact that (for instance) the amino acids in proteins are in the L rather than the D form should lead (mostly, but not always - left-handers still have L amino acids) to people being right handed. Come to that, we do not really have much idea why the chirality of amino acids and other biological molecules should not be the opposite of what it is. So long as they make a consistent choice, there seems to be no very good reason why amino acids in proteins should not be in the D form rather than the L. It may well just be due to some random fluke in the very early history of the evolution of life.

Agreed, one of my favorite cats was a distinct lefty.

I think that handedness may confer advantages in that you can become really good at some things rather than having to learn every task with both hands. If that is true (and it may or may not be,) then most people being right handed may be a random accident brought out by the advantages of being handed.

Why wouldn’t it be randomly 50/50?

It could be 50-50, but didn’t happen to be. Suppose it started out with a slight predominance of right-handers. Then there might have been selective advantages to being right-handed. Nowadays, there is almost certainly an advantage since the world is made for right-handers. But how it got started is a mystery.

Apparently, nearly all women hold their infants with the left hand. Right-handers explain that this leaves their right hand free. Left-handers explain that they do it because they are left handed. This illustrates the difficulty of studying this kind of question.

Yeah, but your dominant hand is predisposed long before you start using it on power tools and scissors.

I can’t imagine natural selection has favoured righties in any way; it doesn’t make sense. There must be something about right-handedness that is genetically encoded.

The question is akin to the one about driving vehices on the right or the left. Each closed culture decided that driving on one agreed-upon side was better than letting everyone drive where they pleased. The choice of which side could have arisen from, for example, which side of the road had a dangerous dropoff when going downhill and under less control. Once a side was chosen, it just kept gaining dominance until it was regarded as “correct”, and objectors were thrown into the volcano, which had a disadvantage in terms of survival.

Handedness could have gone through a similar evolution of selection, in which minority-handed people were discriminated against, which by itself would incrementally keep intensifying the preference for a culturally-approved handedness.

In the northern hemisphere, where most humans and other terrestrial species evolved, the sun and the stars move across the sky from left to right. This would be a highly visible and conspicuous right/left distinction that would be shared in common by all species, and might account for why all animals evolved the same handedness. Exactly how it would contribute to handedness would only be wildly conjectural, but suffice it to say that all animals under the northern sun observe all astronomical motion as a left-to-right phenomenon, thus being aware of their bilateral existence in the same way, in synchronization with each other.

Something a bit longer on facts and logic.

Handedness, in general, confers an advantage. As someone touched on upthread, it’s better to focus on being really good with one hand than it does to be good with the same task with both hands. This pretty much explains why ambidextrousness is rare, and even those who are equally good at some tasks with both hands probably aren’t equally good at other tasks with both hands.

As for why it is right-handed rather than left that is most common, I’d suggest it’s probably just a genetic and social accident, it was bound to be one or the other and right was the one that won. That is, I’d imagine handedness very well could have started out fairly even, but all it takes is a small nudge in one direction or the other early on in our use of tools and our development as a society to push it in a particular direction. Imagine, the first man who develops a tool just happens to learn to use it with his right hand, gets good at it, teaches others to do it like he did, and people who become more proficient with certain tools tend to gain more status and have more offspring. But if the same man had picked it up with his left, we may very well all be left-handed today instead.

I would also imagine this effect would become more pronounced when it came to weapons, for combat, for hunting. People who were more proficient would kill off their opponents and have an easier time feeding themselves. Thus, if there was some social order for being trained to use them right-handed, and there’s some genetic predisposition toward one or the other, those who would have had a bit more natural skill would start to win out and spread that genetic predisposition, even if it is slight.

That’s actually an interesting example. While on vacation in Ireland, we saw a number of castles and one thing the various tour guides pointed out was the stairs spiraled in the towers differently (clockwise or anti-clockwise).

Apparently, this was determined by the handed-ness of the castle’s owner/builder, who would naturally be more comfortable fighting with the dominant hand while retreating up a tower. They said young nobles were trained to fight with both hands but naturally the strong hand would be the better and preferred one.

Huh? Not only are these not mutually exclusive, but that’s how natural selection works. It changes a species’ genetic makeup via having those with undesirable genetics die out.

My mother tells stories about how she showed a preference to left-handedness in school, and the nuns “coaxed” her into being right-handed. Not sure how true that is, but she’s right handed today.

Is there really anyone who is truly ambidextrous? Not someone who is say, right-handed but CAN do stuff left-handed, but someone who shows no preference to either hand?

I’m a lefty in that I write and eat left-handed, but I play golf, throw, and do just about everything else as a righty.

I went to a lot of baseball games in the Nicaraguan Major League, and I noticed that it was very rare for either a pitcher or a batter to be left-handed. Some teams had no lefties at all. I asked my Nicaraguan friend about that, and he offered a speculation. Every kid in Nicaragua, at some time in his young life, works in a sugar cane field. Nobody wants to be a a cane field with a worker who is swinging a machete left handed, so every kid has to learn to cut cane with a machete right-handed, which at least becomes the dominant hand for that kind of motion.

Marvin Benard, who was a Nicaraguan lefty, made it to the American Major Leagues, even though a lefty. It is possible that, among all the right handers in Nicaragua, being left-handed conferred a certain advantage on a player (always facing right hand pitchers, for example), so the simple fact that Benard was left handed might be what made him outstanding enough to attract major league scouts.

A disproportionately large number of major league pitchers are left-handed (about 25%) for the selective reason that a LH pitcher is harder for a LH batter to hit, because of the natural trajectory of the thrown ball. Oddly, about a quarter of all right handed people (and major leaguers) have a tendency to swing a baseball bat in what is known as a left-handed swing, thus creating a need for that many LH pitchers.

First answer the question “Why is there handedness?”

Then come up with some explanation of why right handedness is more common.

I’d give my right arm to be ambidextrous.

I always thought the heart was in the center.

I had both, once, and they used to play in an open faced cabinet I kept my magazines in by one getting inside and the other outside with the wall between them and they’d bat at each other around the wall. But their preferred inside/outside positions were the opposite of their preferred paw. It was funny to watch them each reaching around awkwardly wrong-pawed to bat at the other.

Yes, I’ve known a (very) few. I’m kinda close, in that which way I first learned it is the way I do it, and I have to ask someone who knows which handed I’m doing it. I also do many things either way, just as well. I just have to take a little extra effort to learn the other way, too.

Huh? Your theory only works if all animals were always facing the same direction. The first one to face north instead of south would throw your theory off. I’ve always lived in the northern hemisphere, and I was required under pain of dead (because otherwise I’d tell you the whole idea is silly) I’d say the sun rises on the right and sets on the left. I’m sure that’s a result of reading maps with North on the top.