If you’ve ever witnessed a heated interaction between sporting fans supporting opposing teams, chances are you’ve seen first-hand how much some of us love punching. As a species we’ve even gone so far as to turn it into a sport, several in fact, most of which pull in an outrageous amount of money (according to Forbes, boxer Canelo Alvarez is the 4th highest paid sportsmen in the world, with approximately $92 million in winnings). A recent study published in the Journal of Experimental Biology claims to have uncovered how and why human bodies became so well built for boxing.
Sexual dimorphism is a term to explain the way physical traits can differ between sexes based on how beneficial a particular trait is to their survival. It’s seen in animals such as deer, where male stags sport enormous antlers that help them fight off other males and secure a mate. Sometimes sexual dimorphism can go so far as to be a hindrance to survival, as seen in peacocks whose enormous tails, which are great for displaying, become a handicap when trying to fly. Surviving with such a huge tail proves you must be pretty tough to live on despite your beautiful but ultimately awkward ornament.
In this study, researchers tested the hypothesis that for early hominins, fighting performance between males was a factor that affected their success. They were looking for evidence, or lack thereof, that the ability to punch hard directly affected how likely individuals were to pass on their genes. If punching was favorable, it would surely lead to sexual dimorphism in the form of a musculoskeletal system in males that supports a powerful forward strike.
Using a cranking power output as a proxy for the force involved in punching (understandably, the researchers didn’t want to structure their conclusions on qualitative data based on how it felt to be beaten by their participants), they recorded the punching power of male and female participants. They also measured overhead pulling force between males and females, to see if the physiological bias related more to rock throwing than punching. The results showed a pronounced male-biased sexual dimorphism for propelling the fist forward (which would indicate punching) but very little difference in the overhead arm pulling force (which would indicate throwing).
"In mammals in general, the difference between males and females is often greatest in the structures that are used as weapons," Professor David Carrier of the School of Biological Sciences said in a statement.
Indeed, the support these results provide in favor of aggression shaping physical evolution tie in with his existing research that uncovered the proportions of the hand, as well as enabling dexterity, protect it when balled into a fist. A comparison of primate skulls also found that facial bones were strongest in the areas most likely to get punched, and a further study revealed that heels provide excellent upper body strength when our feet are fully planted on the ground. Each of these characteristics indicates that early hominid’s history of violence may have shaped the evolution of the human musculoskeletal system, leading to the emergence of sexual dimorphism and physical features fit for fisticuffs.
This, of course, isn’t to say that women can’t punch as hard as men. After all, having a slightly more specialized musculoskeletal structure achieves little if you don’t put in the necessary training to back it up. But this research raises interesting questions about how early on in our evolution fistfights emerged and their potential role in shaping our physical development as a species. Nowadays, however, it’s best left to the professionals.