Secrets of the Southpaw

If you’ve ever wondered why some people are left-handed, the answers may lie in the rest of the animal kingdom. Nora Schultz has explored the issue in a fascinating article in the latest edition of NewScientist.

The starting point of Schultz’s piece is the idea that having a dominant side is a feature of most creatures and, as with humans, there is usually a minority which is stronger with the “wrong” side.

The simplest explanation is that many animals share the human trait of brains having different skills handled by different sides of the brain (we recently noted that human brains use a physical divide to do two things at once), which is usually reflected in the dominance of one side of the body.

But surely evolution should mean that the animals for which this isn’t the case would be at a disadvantage and the “flaw” would eventually die out?

It turns out the answer is most likely that having the “wrong” side dominant often produces its own advantages which outweigh the drawbacks. The main advantage is that it can lead the animal to behave and act in a different way, which makes it less predictable to predators.

Another advantage is that having the wrong side dominant is a benefit when it comes to physical clashes with the same species. That’s illustrated by boxing where southpaws are often at an advantage: a southpaw will have spent more time fighting or sparring with orthodox fighters than the other way round, thus being more used to their fighting style. (The same idea applies to non-combative sports such as tennis.) There’s even some evidence to suggest this extends outside of sport and that a left-handed person is more likely to survive a hand-to-hand fight.