Southpaws have always been the bane of right-handers in the boxing ring. And now, science knows why.

Scientists have long known that 10 percent of people worldwide are left-handers. This 1 to 9 ratio between lefties and righties has remained constant for some 5,000 years. Research to find out why this ratio has remained unchanged for so long also confirmed the long-held but unproven "fighting hypothesis" that left-handed people (also called southpaws in boxing) are eminently better fighters than right-handers.

The fighting hypothesis proposed by Raymond et al in 1996 argues left-handedness is, in fact, an evolutionary advantage but maintains this edge only as long as it's much rarer than right-handedness.

The basic idea is this — right-handers don't have much experience in fighting left-handers because lefties are so rare. On the other hand, lefties have a lot more experience fighting right-handers because there are so many of the latter.

The conclusion to be reached is left-handers have an advantage in fighting over right-handers — but only as long as left-handedness remains rare. The rarity of lefties can be explained by the fact most devices are designed for right-handers. This reality means a higher rate of injuries among lefties that use tools designed for right-handers. This is tantamount to an evolutionary disadvantage against left-handedness and helps explain the 10 percent rate of left-handers.

Anecdotal evidence to prove the fighting superiority of lefties is they're over-represented in the Ultimate Fighting Championship and in wrestling, meaning they account for more than 10 percent of the fighters in these martial arts. Scientists, however, said this doesn't prove fighting superiority.

To prove the fighting hypothesis is correct, Thomas Richardson and R. Tucker Gilman from the School of Earth and Environmental Sciences at the University of Manchester in the United Kingdom conducted a study whose results were published in the scientific journal Scientific Reports.

Richardson and Gilman assessed whether or not left-handers actually win more fights than right-handers, irrespective of their numbers in a specific sport. They used a much larger sample than previously studied in their attempt to assess their research question. They investigated 13,800 professional fighters (10,445 male boxers, 1,314 female boxers and 2,100 mixed martial-arts fighters).

Richardson and Gilman found strong evidence supporting the fighting hypothesis.

They were able to replicate the finding left-handers are overrepresented in professional combat sports. They found that among male boxers, 17 percent were left-handers, 12.5 percent were left-handers in female boxers and 18.7 percent were left-handers in mixed martial-arts fighters. This compares to the 10 percent of left-handers in the general population.

Richardson and Gilman also found evidence left-handed fighters actually do win more fights. Looking at the percentage of fights won, Richardson and Gilman found that in all three investigated groups, the average chance left-handers would win a fight was higher than 50 percent. For male boxers, the win percentage was 52.4 percent, while it was 54.5 percent for female boxers and 53.5 percent for mixed martial-arts fighters.

When compared statistically, all of these numbers are significant and shows left-handed fighters are actually more successful than right-handed fighters in combat sports.

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