What determines a person's handedness?

 Most of the human population today is right-handed, something can be seen as far back in the archeological record researchers are able to see, but we still haven’t figured out what truly makes a person right or left-handed. However, here’s what we do know: genetics and environment play a role in determining a person’s handedness. 

While there is no gene that determines left or right handedness, research conducted by William Brandler and his colleagues suggested that the same genes affecting the left-handed symmetry of the organs in our bodies can also affect the way a person’s brain is wired, in turn affecting whether someone’s left or right hand is dominant. 


The environment the person is in can also affect whether they turn out to be left or right-handed. There have been times in the past when right-handedness was forced upon people, for example, teachers would force students to use their right hand and punish those who used their left hand, and some people believed being left-handed was a sign of evil, therefore avoiding the use of it. 

Researchers at Northwestern University created a mathematical model showing that people are rarely left-handed because it is a form of cooperation. Apparently, the balance between cooperation and competition within a species determined the percentage of organisms that were right-handed and the percentage that were left-handed. Humans typically value cooperation, and in doing so, become right-handed as a form of conformity to a social norm, making lefties rarer. 


Several other species also prefer to use one hand over the other, however the ratios are much closer to 50-50. 


Sources: Why Are People Left- (or Right-) Handed? | Live Science, Why are there more right-handed people than left-handled people? | SiOWfa15: Science in Our World: Certainty and Controversy (psu.edu), Righty or Lefty? It's in Your Genes | Live Science

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