Okay, here’s a question most of us don’t know the answer to: why are some people left-handed, while others are right-dominant?
Is it just luck of the draw? Or is there something going on at the fundamental level of the brain here?
It Might Be Genetic
As with so many biological traits, the roots of it seem to be genetic. You can try to force people to deny their biology by putting them on strict diets or tying the offending left hand behind their backs. But ultimately, it’s genes that lie at the root of why many of us are the way we are.
Recently, a study published in the online (and highly reliable) journal PLOS Genetics, discovered what the authors called “a network of genes” that correlate closely with handedness. Right-handed people tended to have one particular configuration, while lefties had another.
What’s more, they think that the differences could have something to do with symmetries in the brain.
Handedness And Language
Following their explanation to its conclusion by tracing brain structures in left-handed people, they’ve discovered that it seems to have a lot to do with language. In other words, the way your brain processes language will largely determine the hand with which you write.
The hypothesis is that handedness is a consequence of the asymmetry in the brain.
Most people process language in the left hemisphere. The theory presented in PLOS Genetics is that this then frees up resources for people to use the right side of their brain for other tasks. Therefore, language processing needs seem to dislodge dominant handedness and transfer it to the other hemisphere of the brain.
Left-handed people, however, are rare examples of individuals who process language in the right hemisphere of the brain. Since they tend to write with their left hand, it suggests that a cause and effect relationship exists.
Of course, there’s been a big push back against the idea that handedness could be genetic. There is a crowd of people who believe that handedness is purely environmental and emerges from early experiences trying to navigate the world. Babies put slightly more emphasis on one side of their body than the other, leading to side-dominance. Science doesn’t need to provide further explanations.
You have to ask, though, whether this idea makes sense. If it were all a result of chance, you’d expect half of people to be right-handed, and half left handed. But that’s not what you see in reality. There are far more people who are right-handed naturally. Ergonomic left handed mouse sales will never approach that of their right-handed counterparts.
The Need For Bigger Studies
To really get to the root of the problem, the authors say that they require bigger studies, perhaps including the genomes of up to 100,000 people. Collecting a sample size this large will allow them to crunch the numbers and definitively say which genes are closely correlated with handedness. Even so, we still won’t know how much of a role nurture plays unless studies accommodate both variables.