Like many complex traits, handedness does not have a simple pattern of inheritance. Children of left-handed parents are more likely to be left-handed than are children of right-handed parents.

Does left-handedness run in families?

Left-handedness runs in families and identical twins are more likely to have the same hand dominant than are fraternal twins and siblings. This implies that the genes do have some influence, but are not the whole story.

What causes a person to be left-handed?

Researchers who study human hand preference agree that the side of the preferred hand (right versus left) is produced by biological and, most likely, genetic causes. ... The D gene is more frequent in the population and is more likely to occur as part of the genetic heritage of an individual.