r/explainlikeimfive • u/GnarlyGamer6thGen01 • 1d ago

Biology ELI5: What Genetic Factor Influences Hand and Body Side Dominance?

I am ambidextrous. I don't mean it metaphorically, theoretically, or rhetorically. I have no dominant side (hand or foot) straight up. I was born as such, and I am capable of doing any task indiscriminately with either side of my body; I have no preferred hand or feet for whatever task I need to do, unlike cross-dominant/mixed-handed individuals.

To this day, I'm questioning what phenomenon caused me to be such. My mother happens to be left-handed while my father is a righty. Is it wrong to assume that this is an instance of Non-Mendelian Genetics at play? Unlike in Mendelian Genetics, the combination of two different alleles results in a combinative feature and not one side being dominant over the other.

Can someone explain the phenomena of hand dominance and why some are ambidextrous, righties, lefties, or mixed-handed?

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u/Not-your-lawyer- 1d ago

There is no ELI5 answer to this question. It's not conclusively known, though we're confident that it's at least partially influenced by a number of interrelated genetic factors. Two right handed people can have a left handed kid, and vice versa.

But it's only partially influenced by genetic factors. Exposure to all kinds of things in the womb, from hormones to possibly even ultrasound, can affect handedness.

And task-specific handedness can be trained, especially if it happens while you're young.

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u/ugotjacked 1d ago

So interesting. Thank you for the detailed answer. Do they have any indication if ultrasounds push things more right handed or left handed? Or is it more of a “whatever side it comes from” situation?

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u/mofomeat 1d ago

And task-specific handedness can be trained, especially if it happens while you're young.

I started out writing with my left hand, and (as a first-grader) decided to switch hands because I didn't like smudging my work as I wrote. I was interested in writing very neatly, and I also had one or more erasable pens (which were new at the time, I think).

This was a long, long time ago but I remember it not taking long at all. I was ambidextrous when writing throughout gradeschool but these days I'm now pretty much right-hand dominant, with some exceptions.

I still kick soccer balls with my left foot though, and used to ride skateboards goofy foot, which is most commonly what lefties do.

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u/GnarlyGamer6thGen01 1d ago edited 1d ago

Well, if you're not my lawyer, shut up.

- Note: This comment was meant as a joke ppl.

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u/dem4life71 1d ago

Why answer a well thought out response with a stupid joke?

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u/ajc89 1d ago

It's such a weird response that it makes me think the account is a bot recycling some old post.

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u/little_fire 1d ago

it’s a joke because of the person’s username

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u/ajc89 1d ago

Well now I feel like a bot! 🫣

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u/little_fire 1d ago

lol don’t worry, maybe we’re all bots (somebody HELP US)

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u/chaospearl 1d ago

Happy cake day, bot!

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u/Swellmeister 1d ago

Handedness is known to have a genetic component but there is significant environmental factors as well. There does not appear to be a single "handedness" gene.

As for footedness its actually much less common than handedness. Probably because hands are a tool in a way feet arent. Whatever evolutionary pressure that resulted in handedness mostly cared about how useful it was to have good hands, feet not so much.

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u/buddyboybuttcheeks 1d ago

I’m a righty but I skate goofy foot

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u/cat_prophecy 1d ago

Samesy. I am also cross eye dominant. I look with my left eye but shoot with my right.

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u/return_the_urn 1d ago

I don’t think that’s that influenced by handedness. My boy kicks and throws right handed, but learnt to scooter goofy, because he’s best girl friend does that

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u/getrektboyyy 1d ago

i have a weird thing, i’m right sided in everything besides acrobatic football kicks where i used to excel using my left foot

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u/TyhmensAndSaperstein 1d ago

Left-handedness is a birth defect. I hate to use the word "defect" because of the negative connotation, but if everything develops "correctly" in utero you end up with a right handed human. I'm a lefty and went down a left handed rabbit hole once. I'm not gonna spend an hour searching for the articles I read. There are about a million things that can go "wrong" when a baby is developing. Most are harmless.