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Left and Right Handedness, what and why?

Left and Right-handedness

Did you know that 90% of the world’s population are right-handers? Aside from parrots we are the only animals on earth that are not split 50-50 with our handedness preferences.

Why? Well we’re not really sure. For the last few days I’ve been perusing the interwebs in search of theories.

And I’ve found a few.

The first thing to consider is Evolution, and place it within relevant history.(Creationists and other Neanderthal-like thinkers look away now.)

The History of Lefties and Righties

Almost every trait/characteristic/piece of anatomy has developed because it is advantageous to its owner in some shape, form or manner.

We as humans got out of the jungles of Africa and started walking on two legs about 2 million years ago. It was advantageous for our predecessors to stand on two feet as they could travel longer distances in search of food. They were therefore less likely to die of starvation and so the trait continued.

Between 1.7million years ago and 800,000 years ago we started making axes, very primitive stone axes (not the gaudy soldier-slaying axes of Tyrion Lannister.)

As part of the research into left and right-handedness, large caches of stone axes found throughout Africa and the Middle East have been checked to find out who made them.

90% of these axes were made by right-handers, 10% by lefties.

So we know that this right and left-handed ratio has been around for longer than we’ve been capable of language.

If we fast-forward into the wonderfully egalitarian and slightly judgemental world of Middle Ages Europe we begin to find some interesting references to left handers:

Largely regarded as the spawn of the devil, as being weak and perverted.

In fact the modern word sinister is derived from the Latin word sinistral, which refers to the left side of something. Even more enlightening is the word Left itself is derived from the Latin word for weak.

Are Left-Handers Weak or Sinister?

Of course they’re not. You should never make assumptions about anyone based on a single trait.

But, awkwardly, left-handers do tend have slightly higher rates of schizophrenia, spinal deformity, immune deficiencies, alcoholism, dyslexia, and there is even a higher correlation of left-handedness and paedophilia.

I must clarify that these are correlations not causations and that we are talking very small percentages. Please… Do not form left-handed lynch mobs.

So what is advantageous about being left handed and how have they managed to survive if everyone has always persecuted them?

Assimilation has to play a part, it’s a right-handed world, to the point that even our manner of writing is tailored to a right-hander, and leaves lefties smearing pens all over the page.

In 2004 French researchers, Dr’s Faurie and Raymond, came up with the ‘Fighting Theory.’

Essentially they set out to test the idea that left-handers were more suited to fighting, and fighting well. Both right and left-handed fighters practise against right-handers. However, due to their scarcity not many people had the opportunity to practise fighting left-handers.

Think practically.

In baseball 50% of the best pitchers and hitters have been left-handers.

Hawthorn FC, premiership winners in the last two years and the most successful club of the last 10 years, has at times had 14 out of 22 left footers on the field.

But in society, lefthanders or left footers, or leftly inclined people only number 10%.

So Faurie and Raymond suggested that in peaceful societies there would be less left-handers and in violent, less settled societies (Western paternalism at play once again) there would be higher percentages of left-handers.

They visited 6 regions and came back with some interesting stats.

The peaceful, pacifist land locked people of Dioula in Western Africa had 3% left-handers in their midst.

Whereas the notoriously violent Yanomamo people of Brazil and Venezuala are 22.6% left handed. And PNG was between 25-30% lefties.

That sounds relatively conclusive right?

Buuuuuuuttttttttt…. when retested by other researchers no such stats were reproduced and so, whilst still floating around the interwebs, Faurie and Raymond’s Fighting Theory has largely been discredited

So what else?

There are a few other theories that are slightly relevant.

The most popular being that.our centre for the control of speech is typically located in the left side of the brain. Speech is a very complex process and it would be logical that if the left side of the brain is very well wired for the motor process of speech then we would be more coordinated in the parts of the body controlled by the left cerebral hemisphere, the right side of the body.

However two thirds of left-handers have their speech control on the left side of the brain and 5% of right handers have their speech control on the right


We don’t know.

On first principles we know that nature likes variety, the more variety there is the greater the chance of a species surviving.

So maybe it is a relic that evolution maintains in case of future disasters.

However that still begs the question as to why every other species is basically equal in their left and right-handedness split and we have preponderance toward right-handedness.

Even more peculiar, why is it that parrots are the only other species that are not 50-50 lefty/righty? And why is it that parrots are 90% left handed?

Apologies to those that got this far only to find that there is no answer.

Personally, I love that there are things in our world that even with all our whizz-bang technology we cannot explain or understand.

Posted in : How the Body Works
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