Field of Science


What Left-Handed Ultimate Fighters Tell Us (or Not) About Evolution

Don't despair, left-handers who have just smeared the ink across your paper yet again. You have a true purpose in life, some scientists say—and it's walloping other people in the head. A flying elbow drop would work too. Researchers recently pored over video of hundreds of UFC fights to test the idea that lefties evolved with an edge in hand-to-hand combat.

Various other animals show a preference for one paw, or one swimming direction, over the other. But humans are notable for almost always preferring the right side. Only about 10 or 12 percent of us are lefties. Is this because there's a cost to being a left-handed human (aside from the ink thing)? Lefties are smaller in stature, and there's some evidence that they don't live as long. If these effects really add up to a raw evolutionary deal, perhaps the reason there are any lefties is that there's some advantage too.

Enter the so-called fighting hypothesis, which says that lefties have persisted at low numbers because they have the element of surprise in a fight.

In order for this theory to make sense, you have to imagine that sometime after our ancestors came down from the trees but before they built weapons, punching each other became very important to their survival. And that despite our squishy outer coverings, valuable dextrous hands, and vulnerable heads, we are a species built for combat. It's a speculative theory. A recent review paper about the fighting hypothesis—which shared an author with the current paper—called evidence for the idea "not particularly strong."

Nevertheless, a group of researchers in the Netherlands chose to explore the theory using mixed martial arts fighters. The UFC "seemed like a very interesting arena to test this hypothesis," says lead author Thomas Pollet, "pun intended." Pollet is a psychologist at VU University Amsterdam. Since the UFC is "a fierce fighting sport hardly constrained by rules," the authors write, it might be a good representation of humans scrapping in an ancestral state.

Pollet studies handedness but didn't have a particular interest in the Ultimate Fighting Championship when he began the study. To get perspective from a fan, I wrote to my friend Ryan, who happens to love watching MMA fighting. He's also a lefty. "A left-handed fighter will lead with their right foot, jab with their right, and cross with their left," Ryan explained. This is all unexpected to an opponent who mainly fights righties. "The speedy jab will come from the opposite side, and the lefty fighter will naturally circle the ring in the opposite direction as well."

Studying recordings of 210 UFC fights, Pollet found that lefties were significantly more common than in the general population. More than 20 percent of the 246 fighters were left-handed. (You can tell by checking their feet; the back leg corresponds to the dominant hand. "UFC fighters only rarely switch between stances within or between fights unless their lead leg is...severely injured," the authors write.)

To look for a left-handed advantage, Pollet analyzed all the fights between a lefty and a righty. The results were an exact tie. A computer simulation in which the fighters' handedness was randomized led to the same conclusion: left-handers had no advantage over righties.

This alone might not disprove the fighting hypothesis. That's because the UFC represents the cream of the lawless-brawling crop. "A fighter must go through a minor league promotion in their home town before making it to the big stage," Ryan told me. On their way to the professional level, left-handed fighters might have an advantage, which would explain why there are so many of them in the UFC. But once they become more common—and face more opponents who are experienced at fighting lefties—their edge might disappear.

"I think it is a very attractive hypothesis," Pollet says. The advantage of being left-handed in a fight may depend on how many other lefties are around, but "testing frequency dependence can be hard," he says. He's hoping to compare results in the UFC to other competitions that include more amateurs.

Currently, Pollet and his colleagues are working on a meta-analysis of lefties in different sports. In tennis, for example, being left-handed can give players a boost. (My friend Ryan, who just happens to also play tennis, said that being a lefty gave him "a great advantage growing up." A lefty cross-court forehand shot, he explained, forces your right-handed opponent to return the ball with a weaker backhand.)

In addition to the UFC, left-handedness is especially common among badminton players, cricketers, and recent U.S. presidents. Maybe lefties can look to those areas to find their evolutionary reason for being. If they still feel existential angst, they can always go out and punch someone.

Image: by Krajten (via Wikimedia Commons)

Thomas V. Pollet, Gert Stulp, & Ton G.G. Groothuis (2013). Born to win? Testing the fighting hypothesis in realistic fights: left-handedness in the Ultimate Fighting Championship. Animal Behaviour DOI: 10.1016/j.anbehav.2013.07.026

Thanks to Ryan Sponseller for his thoughtful comments on handedness and punching dudes.

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