A couple of interesting bits of research on handedness in the news today.
Chimps brains are asymmetrical in similar ways to human brains, and this is reflected in whether they’re left or right handed too. Why we have a preferred hand is still being debated, but this research shows handedness isn’t a consequence of the same brain asymmetry which arose with language (the language centres are on the left side of the brain). Handedness must have arisen much earlier, and been present 5 million years ago.
In Mind Hacks, in “Test Your Handedness” [Hack #68], Karen Bunday points out one theory arguing that hand preferences come from our tree-dwelling past. One hand is mainly used for hanging on to branches, and the other hand used for finer, manipulative tasks like picking fruit. The difference in the hemispheres of the brain comes about when each optimises for slightly different behaviours. For example, spider monkeys tend to reach with their left hand. Use the keywords Postural Origins to search for more. (Personally, the idea that our brains were shaped by the literal shape of the forest canopy and the tree branching structure fascinates me. I’d love to know more about this, so recommended reads are much appreciated).
Which posturing brings us to the second piece of handedness research, related by BBC News Online: Left-handers ‘better in fights’, as found by looking at homicide rates in traditional societies and their left-handedness rate. Without reading the paper I couldn’t be sure, but it can’t be easy to get a causual relationship out of that, and the article does quote some sensible objections. But hey, it’s a great headline.