Day five of the ‘Blogging from A-Z Challenge’ and I’m thinking about evolution. Why has right-handedness become apparently dominant over left-handedness even though there is little evidence for a genetic leaning?
Do animals show the same traits?
It is a well-known fact that polar bears are left handed. They sneak up on prey by covering their nose with their right paw (their nose being black and therefore showing up against the snowy white background), then club it mercilessly with their left paw. Like all well-known facts it is clearly not true. Polar Bear’s eyes are black as well which would put the kibosh on this theory. I did read however of a polar bear that may have had a right paw preference. When hunting, it would cover its nose with its left paw and raise its right, become flustered and begin to switch, bonk itself painfully in the nose, and usually lose its prey. It didn’t survive long. Some polar bears were also observed to squint their eyes almost closed to be even less conspicuous.
Before I go further into this though I was going to cover the subject of being evil in this blog. When I was in my teens, one of our neighbours, called Nick told me of how he had grown up in South Africa. He had shown a natural propensity for using his left hand. This had horrified his teachers as it was the mark of the devil. They ended up tying his left hand behind his back until he was proficient enough with his right. I wonder if this is still in the curriculum.
I’ve trawled the net and found little evidence that animals have a hand preference. I’ve found plenty of rumour and speculation however. Even the primates seem to be even-handed (a euphemism for being fair) or even-pawed. Individual animals do show a tendency to lead with their left or right and are remarkably reluctant to change even if pushed. The left / right mix remains approximately equal however and even breeding same handled animals doesn’t make a difference.
Contentious studies still go on for example at the Yerkes Regional Primate Research Center in the USA. Here it has been claimed that captive chimpanzees show a greater bias for right-handedness where the task requires high levels of dexterity which rises to almost one hundred per cent for some specific tasks, such as over-arm throwing. Every day food related activities remain even handed. These scientific claims remain hotly disputed.
Only one other animal seems to show a distinct hand, or in this case claw, bias and that is the parrot. I’m not sure that every animal has ever been tested yet it turns out that over ninety per cent of parrots tend to prefer to cling onto the branch with their right claw and pick up objects with their left.
So where does this leave us? Why are there such distinct differences in handedness between humans and other species? Has handedness conferred an evolutionary advantage? I’ll come back to this in a later blog piece.