left-handed

Credit Podzo di Borgo – CC-BY-SA

A while back I was sitting with some friends and relatives and we were having a conversation. We were talking about creative people. Writers, actors, dancers, etc. We were remembering how it seemed like in the olden days actors all had to be able to sing and dance as well. Acting well wasn’t enough. You had to be able to do it all.

One of my relatives said, “I know a guy who’s both an actor and a dancer.” Good. Someone keeping up the tradition.

As a complete non sequitur, I said, “Oh, what are the odds he’s left-handed?” I thought the odds were pretty good because it seems like a higher than average percentage of creative people are left-handed. Not very scientific, and not really supported by evidence either, but a harmless pop culture conversation. So far, so good.

But I lied to you. That’s not what I said. What I said was, “Oh, what are the odds he’s gay?” Uh-oh. Not so harmless anymore, is it?

So, why am I saying this? Why am I outing myself as a completely reprehensible human being? Well, I’m not. I don’t think there’s any difference between saying, “What are the odds he’s left-handed?” and “What are the odds he’s gay?” And not just because it seems like a higher than average percentage of creative people are gay, too. Another pop culture observation, also unsupported and likely untrue, but reliable conversation fodder.

To me, there’s nothing wrong with saying it. To me, those two phrases are equivalent. What is wrong is that we think they’re different, and as long as we think that, then we’re not where we need to be as a society.

What do you think?

rjb

Photo credit – Unhindered by Talent

Humans show a strong preference in which hand they use for most tasks. The things that require the most dexterity and fine control are done by our preferred hand. Things like writing, for example, people do well with one hand and horribly with the other. The majority of people, around 90%, are right-handed. Most of the remaining 10% are left-handed, and a few are ambidextrous, or equally able with both hands.

Credit Guy Rich Caswell – Public Domain

There has been debate and disagreement as long as can be remembered about handedness. Why is it there? What causes it? Does one’s handedness indicate the presence or lack of moral rectitude? Well, that last question is positively anti-scientific, but that doesn’t stop it being asked.

As for what causes handedness, it’s been shown that the distribution of it and the hereditary nature of it indicate that it’s genetic. Not only that, but it’s most likely that it’s all down to one gene with both a dominant and a recessive version. A child’s handedness is determined by which versions of the gene the parents have.

— More studies have complicated things. It’s now thought that only about a quarter of the determination of handedness is by genetics, and three quarters by environmental factors. Refer to the Wikipedia article on handedness.

The two forms of the gene aren’t simply a right-handed version and a left-handed version. If that were so, it wouldn’t explain how two left-handed parents could have a right-handed child, or how identical twins can sometimes be oppositely handed. Instead, the researchers are describing the dominant version as right-handed and the recessive one as random. So, of the pair of copies of the handedness gene that a child gets, if even one is dominant they are right-handed. If both are recessive then the child could be left- or right-handed. Hence the definition of the recessive gene as random.

Oddly, there’s a link between handedness and the direction the hair grows. As the hair swirls away from the crown of the head it either turns to the right, clockwise, or to the left, counterclockwise. Almost all right-handers have clockwise whorls, while left-handers and the ambidextrous have whorls which randomly go one way or the other.

The one gene seems to be both a right-handed/random gene and a clockwise whorl/random gene. If you get two copies of the random variant from your parents you have a 50/50 chance of being left-handed, and if you’re left-handed you have a 50/50 chance of having a counterclockwise hair whorl.

And now, after all that, here is something that might debunk the whole idea of a link between handedness and hair whorls. For that, go to the University of Delaware and their series on the Myths of Human Genetics.

rjb