What makes you a righty or a lefty?

The GLP aggregated and excerpted this blog/article to reflect the diversity of news, opinion and analysis.

About 90 percent of us are righties — though the rate can vary by country and time period. Also, almost all the information we have on this comes from Western countries after the year 1900. As you grow up, you will learn to raise a mighty eyebrow at generalizations taken from such limited data. Sometimes, though, it’s all you’ve got.

Here’s what we do know: Humans are pretty asymmetrical creatures. That applies to both how we use the body parts we have and where things are in the first place. Our hearts tend to be on the left. Our livers tend to be on the right. Not only do these asymmetries exist, but some of them seem to be interconnected. People who are right-handed tend to process language on the left side of their brain.

In 2013, a paper published in the journal Heredity demonstrated that handedness had to involve more genes than was originally thought — a lot more. The researchers analyzed the genomes of 3,940 twins whose handedness was recorded from previous studies. First, they found that identical twins, who share all the same genetic material, weren’t significantly more likely to have the same dominant hand than fraternal twins, who are just regular siblings who shared a womb. That alone starts to rule out simple genetics.

Read full, original post: Why Am I Right-Handed?

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