Being Left-Handed

For the left-handed people of the world, life isn’t easy. Throughout much of history, massive stigmas attached to left-handedness meant they were singled out as everything from unclean to witches. In Medieval times, writing with your left-hand was a surefire way to be accused of being possessed by the devil; after all, the devil himself was thought to be a lefty. The world has gotten progressively more accepting of left-handed folk, but there are still some undeniable bummers associated with a left-handed proclivity: desks and spiral notebooks pose a constant battle, scissors are all but impossible to use and–according to some studies–life-expectancy might be lower than for right-handed people.

What makes humanity’s bias against lefties all the more unfair is that left-handed people are born that way. In fact, scientists have speculated for years that a single gene could control a left-right preference in humans. Unfortunately, they just couldn’t pinpoint exactly where the gene might lie.

Now, in a paper published today in PLOS Genetics a group of researchers have identified a network of genes that relate to handedness in humans. What’s more, they’ve linked this preference to the development of asymmetry in the body and the brain.

In previous studies, the researchers observed that patients with dyslexia exhibited a correlation between the gene PCSK6 and handedness. Because every gene has two copies (known as alleles), every gene has two chances for mutation; what the researches found was that dyslexic patients with more variance in PCSK6–meaning that one or both of their PSCK6 alleles had mutated–were more likely to be right-handed.

The research team found this especially interesting, because they knew that PCSK6 was a gene directly associated with the development of left-right asymmetry in the body. They weren’t sure why this would present itself only in dyslexic patients, as dyslexia and handedness are not related. So the team expanded the study to include more than 2,600 people who don’t have dyslexia.

The study found that PCSK6 didn’t work alone in affecting handedness in the general population. Other genes, also responsible for creating left-right asymmetry in the body, were strongly associated with handedness. Like PCSK6, the effect that these genes have on handedness depends on how many mutations the alleles undergo. Each gene has the potential for mutation–the more mutations a person has in any one direction (toward right handedness or left handedness) the more likely they are to use that hand as their dominant hand, or so the researchers speculate.

Read more: http://www.smithsonianmag.com/science-nature/why-are-some-people-left-handed-6556937/#GmmcyZmHiDHgmBlR.99
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