Dr. Universe,

Why are people most commonly right-handed? Who/what deicides if we are left-handed or right-handed? Are you left-handed or right-handed?

— Mya, Alexandria, Va.

We don’t know exactly why so many people are right-handed, but one place we might look for answers is in the material that makes a person who they are: genes.

The genes in your body help control all sorts of things, from the color of your hair to your skin to your eyes. These traits can be passed down through generations — from grandparents to parents to you.

My friend John Hinz, who is a right-handed professor at Washington State University, knows a lot about genes and the study of how organisms pass their genes through generations.

He said that while there isn’t a single gene that helps determine if you will be right-handed or left-handed, scientists have found around 40 genes that seem to be related to handedness. Sometimes there is just one gene that causes a certain trait, but often it is combinations of genes that contribute to each of your characteristics.

“Genetics is clearly part of it but not the whole story,” Hinz said.

He also said when both parents are left-handed, they are more likely to have a child who also is left-handed. Some studies have shown that if both parents are right-handed, there is a 10-percent chance of having a child who is left-handed. Meanwhile, if both parents are left-handed, there is about a 25-percent chance the child will be left-handed.

But all we have to do is look at twins to realize there is more to it. Identical twins have all the same copies of every gene, but they don’t always use the same hand.

This question has left a lot of researchers wondering about the very question you’ve asked, Mya. People have looked into how the language centers in our brains might be connected to our handedness or how our experience as babies might be connected to our handedness. Some researchers have even observed dominant hands as a fetus develops in a mother’s womb.

They’ve also investigated how people’s different abilities are connected to handedness. Of course, just because there are a lot of connections or correlations between what hand a person uses and other traits or behaviors, that doesn’t mean we can say for certain. We haven’t found a clear answer to your question. Yet.

Whether you are left-handed, right-handed, or both-handed, hands can be really helpful tools. They can help us pick up things, climb to great heights, and even give a high-five. Perhaps one day you can join the community of creative and smart scientists to help us investigate more about genetics and handedness. There’s still a lot of research to do among our four-legged animal friends, too. As for me, I’m a righty. How about you?

Have a science question? Ask Dr. Wendy Sue Universe, WSU’s resident science cat and writer, by email at Dr.Universe@wsu.edu, on her website at askDrUniverse.wsu.edu, via Twitter at @AskDrUniverse or at facebook.com/AskDrUniverse.

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