Why fighting gives lefties the upper hand in evolution
Departments 13th August 2019
The slight advantage left handed fighters have may be the reason that natural selection hasn’t weeded them out. To mark International Left Handers Day, we take a look at why southpaws have an advantage in the ring.
Left-handedness poses something of a mystery for evolutionary biologists. Across the animal kingdom, the ratio of right to left-handedness (or should that be pawedness?) is 50:50. In humans, the right/left bias is approximately 90:10. So, lefties account for just one in ten of us.
This unusual split is a mystery, but another riddle is why left-handedness has persisted throughout 200,000 years of modern human evolution. When left-handedness is so rare, why hasn’t it been weeded out by natural selection?
Being left handed is linked to several unexpected and unwelcome consequences. For example, left-handers tend to have a lower birth weight and a shorter life expectancy. They are also at an increased risk of being diagnosed with certain mental health conditions. Again, when there seem comparatively few benefits to left-handedness, logic dictates that natural selection would put paid to it. And yet it persists.
Research from The University of Manchester may have now cracked the case – and it’s all down to the abilities of those tenacious lefties in combat.
Thomas Richardson of the Department of Earth and Environmental Sciences is an evolutionary scientist – and also, helpfully, an amateur boxer. Together with Dr Tucker Gilman, he conducted research across nearly 10,000 male and female boxers and mixed martial arts fighters – the largest sample ever examined.
Taking a random left-handed fighter from the selection and comparing their win record to a randomly selected right-handed fighter, Richardson found that the leftie would have a greater number of wins between 53 and 54 per cent of the time. It may seem like a small margin, but it’s been a big advantage for lefties when it comes to human evolution.
Fighting for survival
It has long been questioned just why one in 10 of us are lefties. Your hand bias is determined by genetics – as many as 40 different genes, to be precise. If your parents are left-handed, you’re more likely to inherit this trait.
However, when the percentage of lefties is so slight, you would think that hundreds of thousands of years of human evolution would have sifted out the trait. The Fighting Hypothesis, which Richardson’s yet-to-be peer-reviewed research supports, is one reason why left-handedness may linger.
Basic maths dictates that left-handers are more likely to meet right-handers in combat. This means they train to fight right-handers. On the other hand (!), right-handers only have a one-in-10 chance of fighting a left-hander or training against one. As a result, the stance of a southpaw can throw a right-handed opponent and negatively impact their fight.
Throughout history, this advantage has given lefties the upper hand in combat. The Roman emperor Commodus – who Joaquin Phoenix portrayed in the film Gladiator – was a leftie, and famously bragged of conquering “twelve times one thousand men”. He liked to fight as a gladiator and had a staggering success rate – probably due more to all his opponents having to submit to the emperor than to him being left-handed.
Some two thousand years after the reign of Commodus, boxing champions Joseph Calzaghe and Oleksandr Usyk are both lefties, and southpaws continue to keep right-handed boxers on their toes in the ring. When it comes to hand-to-hand combat, left-handedness is a good advantage to have – and so the genes responsible for it continue to be passed down to new generations thanks to sexual selection.
The upper hand
“Left-handedness per se confers no fighting advantage, it only has an advantage because it is rare, and rare fighting styles have the advantage,” Richardson explains. “In fact, the rarer they get, the more of an advantage they have.”
This explains why Richardson found that not only were the lefties in his sample more likely to win more fights, but also that the proportion of leftie fighters is slightly greater than the proportion of lefties across the population as a whole. However, it’s a delicate balance to strike.
“If left-handers get too common, everyone learns how to deal with them and they lose their advantage, which is why they don’t take over the population. But when they are extremely rare, they have a very large advantage, which stops the left handed genes going ‘extinct’,” says Richardson. Simply put, if too may lefties pull on the boxing gloves, right-handers will get more experience fighting them and the southpaw advantage will be lost.
The mysteries of left-handedness don’t end there, though. We suggest you spend this International Left Handers Day unravelling a few more leftie mysteries (and celebrating that left-handedness no longer gets you accused of witchcraft). Or, you could follow Richardson’s advice: “In the spirit of our evolutionary past, I suggest that male lefties mark the day by fighting another man for his resources!”
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Words – Hayley Cox