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Techly Explains: Why are only 10% of people left-handed?

There’s an old adage that you don’t really know someone until you’ve walked a mile in their shoes.

However, if you’re lucky enough to be in the minority of humans born left-handed, the list of daily struggles that the general populace can never understand just seems to go on forever.

Whether it’s being universally hated by classmates for always bumping elbows with them when writing, the awkwardness that comes with having to use right-handed scissors, or even the dirty looks that come with some ancient superstitions about your preferred hand, left-handedness is an exclusive club that alters life in ways many of us would rarely even consider.

It’s surprising then, that for such a topic there seems to be so much speculation about, we as a society seem to know alarmingly little about the actual causes and implications of left-handedness. It’s fairly well accepted in the scientific community that humans as a whole tend to favour various body parts for different tasks – 40 per cent of us are left-eared, 30 per cent are left-eyed and 20 per cent favour our left foot (you can find out which side your brain favours here).

However, only about 10 per cent of us are left handed. The reasons behind the relative rarity of this preference compared to other biases, though – and indeed, why such a split even favours one side over the other – have baffled us as humans for longer than we’d like to admit.

It’s long been thought that left-handedness is more common in certain groups of people – for example, artists, writers, musicians and other creative types. However, the root of left-handedness can be seen in some of our closest living relatives on the planet, the great apes. For specific tasks, whether that be termite hunting, or fruit-picking, chimpanzees seem to favour one hand over the other – allowing them to develop their neurocognitive and nervous pathways to become more accustomed to, and, ultimately, better at, certain tasks.

This evolutionary advantage doesn’t explain as much as it seems to at first, though. Upon closer inspection, the split of specialisation in chimpanzees is roughly 50 per cent left and 50 per cent right. How, then, did humans end up with such a skewed split?

Ned Flanders' Leftorium - screenshot from 'The Simpsons'

As with many traits, behavioural and physical, the answer may lie in our DNA, with our genes providing clues as to our evolutionary history and predispositions. As it turns out, one of our closest primitive relatives, the Neanderthals, also displayed tendencies to favour one hand over the other.

Studies of Neanderthal teeth have revealed characteristic scratches and marks – a result of contact with stone implements used to cut meat while Neanderthals anchored the food with their teeth. Surprisingly, the ratio of Neanderthal skulls displaying these marks on the right side to the left is the same as the proportion of right-handed humans to left-handed ones – 9:1.

Given that interbreeding between early humans and Neanderthals is fairly well documented, the chance that the Neanderthal genetic code may have had some influence over our own, and therefore, our predisposition for left-handedness, is at least worthy of consideration. Gene mapping, however, is a complex process, with genes often working in tandem to produce varied effects, as opposed to having a direct correlation to certain characteristics.

At present, it’s estimated that in excess of 40 genes may contribute to one’s predisposition for using a certain hand, and untangling the complex web of relationships amongst these genes is a task that’s only just beginning for many scientists.

Left-handers can take solace in one thing, though – if the superstitions about you guys being evil hold any water, then simply training yourself to write with another hand won’t do it. That trait is burned into your genes – you might as well own it.

About the author

Karl is the physical embodiment of an alternate universe where Kurt Cobain played for Hanson, instead of Nirvana. When he’s not furiously bashing a keyboard and howling in pain, he can probably be found mumbling into a microphone somewhere, or up in the gym working on his fitness (with Fergie as his witness)

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