Is Left-Handedness Determined by Genetics?

There may be people in your family tree who were left-handed. In some cases, this could be influenced by genetics. However, genetics do not always play a part in handedness. It is not as simple as in features that are determined by either dominant or recessive genes (such as eye color).

The U.S.National Library of Medicine says that left- handedness is a complex trait that appears to be influenced by multiple factors, including genetics, environment, and chance. In Western countries, 85 to 90 percent of people are right-handed and 10 to 15 percent of people are left-handed.

Hand preference begins to develop before birth. It becomes increasingly apparent in early childhood and tends to be consistent throughout life. Hand preference probably arises as part of the developmental process that differentiates the right and left sides of the body (called right-left asymmetry). Handedness also appears to be related to differences between the right and left halves (or hemispheres) of the brain.

There was a time when it was thought that a single gene controlled handedness. Recent studies suggest that multiple genes, perhaps up to 40, contribute to handedness.

Researchers have found that the PCSK6 gene has been associated with an increased likelihood of being right-handed in people who have schizophrenia. Another study found that the LRRTM1 gene is associated with an increased chance of being left-handed in people with dyslexia. The thing to keep in mind is that it is unclear whether those genes relate to handedness in people without those conditions.

In some cases, handedness is influenced by a person’s environment.

For example, the left hand is considered to be unclean in India. People are expected to avoid having their left hand come into contact with food, people, or objects that can be passed to people. Researchers found that in Taiwan, about 60 percent of left-handed students are forced to convert to right-handedness.

Related Articles at FamilyTree.com:

* Who Was Left-Handed In The Family?

* Genetics, Culture, and Left-Handedness

* Gene Mutation Links Dyslexia and Handedness