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Genetics, Culture, and Left-Handedness

Genetics Culture and Left Handedness  Find more genealogy blogs at FamilyTree.comAre you right-handed, or left-handed? Today, that answer to that question is little more than an interesting bit of trivia. In the past, however, there was a stigma attached to left-handedness. It turns out that there is some genetic influence that connects to whether a person is right-handed or left-handed.

What’s behind the stigma on being left-handed? Some of it has to do with superstition. The Anything Left Handed blog has a list of folklore and superstitions that paint left-handed people in a bad light.

One you may have heard of has to do with salt. There was a superstition that evil spirits lurked over a person’s left shoulder. The way to get rid of them was to throw salt over that shoulder to ward them off. This same technique was said to ward off the devil.

Some religions connect left-handedness with evil. Christianity, for example, includes beliefs that connect the left with evil. The Anything Left Handed blog says the bible has over 100 favorable references to the right-hand, but that the left-hand is only mentioned in reference to evil.

Did your parents or older relatives attend a Catholic school? It once was a common practice for nuns (who functioned as teachers) to force left-handed children to become right-handed. Maybe the nuns believed they were warding off evil?

There were other, more practical, reasons to teach children who were left-handed to become right handed. The Industrial Revolution probably had some influence on this. Machines were designed with right-handed people in mind. Children were using steel dip pens that needed to be dragged across the paper in a way that was designed for right-handed people.

A paper published in PLOS Genetics suggests that there is a genetic link to left-handedness. A gene called PSCK6 is directly associated with the development of right-left symmetry in the body. It appears that the number of PSCK6 alleles that have mutations matter. People with mutations on one or both of their PSCK6 alleles are more likely to be right-handed.

There is still a lot to learn about exactly how genes influence left-handedness. What is known is that 90% of humans are right-handed, and 10% of humans are left-handed. There seems to be some interest in trying to figure out if different types of animals are right-hand or left-hand dominant.

In 1986, National Geographic produced a unique issue that had a scratch and sniff card. People tested it and were asked to send back information about what the card smelled like to them. The people also filled out a questionnaire.

The goal was to see if there was a connection between handedness and smell. Turns out, there wasn’t. Instead, National Geographic ended up with the largest data set of hand preference ever constructed.

Image by Dave Haygarth Flickr.

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