Right or left handedness is not simply inherited from your parents.
A lot of research has been done into why people are right-handed, left-handed, ambidextrous (use both hands equally well) or mixed-handed (when they favour different sides for different tasks).
No simple answer has been found.
About 85% of humans are right-handed, and inherited genes seem to play a part in this.
For example, one study found that a child of two left-handed parents had a 26% chance of being left-handed – compared to a 19% chance if they had one right-handed and one left-handed parent, and a 9% chance if both parents were right-handed.
Twins have been the focus of much research, and the fact that identical twins can favour different hands suggests handedness is not a totally genetic trait.
Some researchers have found links between left-handedness and problems in pregnancy, birth trauma or even childhood illnesses.
But even if these do play a part in some cases, it would not explain left-handedness in people with no past health problems.
So we don’t know for sure why some people are left-handed, but we do know that even a child of two southpaws is most likely to favour their right hand.