Friday, March 26, 2004

The Value of Left-Handedness

It seems that left-handedness was as common in the Ice Age as now. This article suggests that:

" Left-handedness may have conferred prehistoric man advantages, such as in combat, say the researchers. "

If left-handedness did indeed confer benefit in combat, it might have been because of the "surprise value" of having to fight a left-hander. Since such a surprise value would only be effective if left-handedness were relatively uncommon, this might explain why it is found in only a quarter of the population, or less.

That is, there would seem to be an optimal level of occurrence of left-handedness. If it were too common it would lose its survival value. Some traits are like that. It is called (negative) frequency dependent selection.

The article claims that handedness is partly under genetic control. So it seems feasible to me that left-handedness is an example of a trait that is maintained in the human population because it is useful to people who have it, provided it does not become too common.

How much of an advantage is it to be a left-hander in a fight? I am not aware of any systematic studies, but people who write about boxing in America refer to "southpaw [left-hander] advantage". An example:

" And his southpaw advantage shouldn't be minimized, Ayala said.

"I know Bones has faced some southpaws, but I'm an extremely good southpaw," Ayala said. "I'm not a walk-in-the-park southpaw." "



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