Arm length is associated with fighting success among mixed martial arts fighters, even when controlling for body size, according to new research published in Evolutionary Behavioral Sciences.
The findings suggest that human males may have evolved to have longer arms than women because it gave them an edge during combat in our ancestral past.
“I became interested in this topic as an offshoot of another project (which got a lot of media attention) on left-handedness, and how it may have helped our male ancestors in combat,” said study author Thomas Richardson, a PhD student in at the University of Manchester.
That study, published in the journal Nature, found that left-handed boxers and MMA fighters were overrepresented in their respective sports and also tended to be more successful fighters.
“There’s a lot of evidence now that fighting and warfare played a large role in our evolutionary past and shaped who we are today. I’m interested in how thousands of years of combat and warfare have driven the evolution of the male body and behaviors. Combat sports are one promising avenue for testing these hypotheses,” Richardson said.
For his new study, Richardson analyzed data from 1,660 modern MMA fighters provided by UFCstats.com. After controlling for the effects of sex, height, and weight, the researcher found that arm span had a significant effect on the fighters’ win percentages.
In particular, fighters with longer arms won a greater percentage of their fights. This effect, however, was small. “In the present study, a 5-cm increase in arm span would only typically result in a 1% increase in fights won,” Richardson wrote in his study, adding that the small impact of arm span highlights that “success in modern MMA is likely determined by complex interacting factors.”
“As this work is quite preliminary, I’d say to take this study as inspiration rather than statement of fact. I hope it encourages readers to think about how their body evolved to be the way it is,” Richardson told PsyPost.
“Our physical selves can influence our psychology and behavior, but our behavior can also influence our species’ evolution and shape our bodies. It also illustrates that evolutionary changes don’t have to be large and dramatic. Most are small tweaks, but even a slightly longer arm span might have large consequences over many generations.”
“This work is early days. It’s very difficult to demonstrate conclusively that something evolved for a specific purpose, especially in a species where we cannot directly observe evolution. As Evolutionary Behavioral Scientists, we need a diversity of evidence,” Richardson added.
“My study brings to the table a lot of data on real fights, but genetic studies, studies in modern hunter-gatherer populations, and computer simulation studies would be valuable in testing this hypothesis thoroughly. And of course, I encourage direct replication of my work!”
The study, “Is Arm Length a Sexually Selected Trait in Humans? Evidence From Mixed Martial Arts“, was published June 4, 2020.
