Answer: Although no definite gene has been determined to cause lefthandedness it does seem to run quite strongly in families. It is not predictable based on the handedness of parents and grandparents in the same way as eye colour but the handedness of the parents does seem to be a significant overall factor in determining the handedness of the children.
As an overall average, the percentages are something like this:
Two right handed parents, 9%
Left handed father, 12%
Left handed mother, 16%
Two left handed parents, 20%
Some interesting figures come out of these statistics:
- More than 50% of left-handers do not know of any other left-hander anywhere in their living family.
- Around 75% of left-handers have two right-handed parents and only 2% have two left-handed parents.
- Between 7 and 8 out of 10 children born to two left handed parent will be right handed.
Of course, the chances of having a left-hander in the family increase the more children you have. So there is still hope for right-handed parents – if you have enough children, you may still be lucky enough to have a left-hander!