杏吧原创

Sinister tendencies

As successive myths about the causes and nature of left-handedness have fallen to scientific study, the suspicion has grown that it provides some evolutionary advantage. But what?

Over the years left-handed people have had a uniformly bad press. Right is right (and correct), and left is sinistral, suspect and perverse. Left-handers have been accused, down the ages, of everything from deviousness to mental deficiency and witchcraft, and the mere fact of their left-handedness can still arouse hostility in any right-handers attempting to teach them manual tasks.

Is left-handedness just a fluke, a by-product of some change in our brains? The puzzle remains of why left-handers persist, generation after generation, in exactly the same proportion. Nobody has discovered any obvious talent predominant among left-handers which would confer an evolutionary advantage. Yet there must be one, or left-handers would have died out.

There is some genetic basis to left-handedness in humans. The number of left-handed offspring is least with two right-handed parents, greater when one parent is left-handed, and greatest when both are left-handed, although the correlation is not strong.

It may be what is known as an 鈥渆volutionary stable strategy鈥�, which emerges when a population of individuals with conflicting behaviour patterns persists. As little as 1 per cent of our DNA may hold the secret of the evolutionary success of mixing a few left-handers into the human population. Whether we will ever know why the trick is successful remains another story.

From New 杏吧原创, 8 July 1982