In 1996, a study to determine handedness within 1700 Dutch families containing a pair of twins was undertaken to see if genetic inheritance had a bearing. I won't bore you with all the details but suffice to say they looked Double Dutch to me.
It showed that 25% of the twins born to two left hand parents became left handed and the same again if one parent was left handed and the other right handed, particularly if the mother was left handed too.
It showed that 25% of the twins born to two left hand parents became left handed and the same again if one parent was left handed and the other right handed, particularly if the mother was left handed too.
One other theory is that society often encourages naturally left handed people to adopt right handed habits, which masks the true number of leftys. A study on 687 Ohio State University student families discovered half of the children from a left hand to left hand marriage were left handed.
So it is difficult to tell how exactly one becomes left-handed. Population genetics suggest an inheritable basis, but we can only guess until a specific gene or pathway is discovered.
It has been postulated that becoming left or right handed is random unless a single gene called right-shift (rs) is present. If it is, then a person is more likely to be right-handed. If the birth was stressful or low in weight then there is a higher incidence of being left handed.
As for those that are ambidextrous, we think they are just indecisive.
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1 comment:
Very interesting study and I thought it was funny how being ambidextrous leads to indecisiveness. Sometimes I can't decide which hand I want to use to do something, hahaha.
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