Distance running may be more than just a sport or hobby for men when it comes to mating. Distance runners have higher levels of testosterone and genetic leverage over their male competitors, according to a new study published in the journal PLOS ONE. Researchers from the University of Cambridge’s Division of Biological Anthropology measured half-marathon runners’ finger length as a marker for hormone exposure in the womb.

To provide a little background, a recent study found the smaller the ratio is between a man’s pointer finger and his ring finger, the less testosterone he was exposed to while in utero. Previous research has found pre-birth hormone exposure has been shown to increase sex drive, sperm count, cardiovascular efficiency, and spatial awareness. Babies who were exposed to higher levels may have also been born with an advantage on the track. Knowing this, researchers analyzed 542 runners’ finish line times and photocopies of their hands, and found the faster the man, the higher the testosterone level according to his fingers.

"The observation that endurance running ability is connected to reproductive potential in men suggests that women in our hunter-gatherer past were able to observe running as a signal for a good breeding partner," the study's lead author Dr. Danny Longman, a researcher from the University’s division of biological anthropology, said in a press release, adding:

It was thought that a better hunter would have got more meat, and had a healthier — and larger — family as a consequence of providing more meat for his family. But hunter-gatherers may have used egalitarian systems with equal meat distribution as we see in remaining tribes today. In which case more meat is not a factor, but the ability to get meat would signal underlying traits of athletic endurance, as well as intelligence—to track and outwit prey—and generosity—to contribute to tribal society. All traits you want passed on to your children.

From an evolutionary standpoint, males with better athletic endurance “signal” a primitive desirability in females who view this as a positive cue for strong genes. It all goes back to human ancestral history of the hunters and gatherers. The men who proved to be better providers were also the persistent and tireless hunters who exhausted their prey. Long distance runners of today were more likely to have been good hunters and ultimately desirable providers for their mate and offspring, according to the research team's theory.

"Humans are hopeless sprinters," Longman said. “Rabbits, for example, are much faster sprinters, despite being fat and round. But humans are fantastically efficient long-distance runners, comparable to wolves and wild coyotes. We sweat when most animals would overheat; our tendons and posture are designed to propel our next strides — there was likely a selective pressure for all these benefits during our evolution."

A woman today innately translates the running theory into an indication males have other key traits for being a good provider, such as intelligence and generosity. Finding a good mating partner is consistent between both genders; however, female ancestors were stay-at-home gatherers in the past, which ultimately built the foundation of the modern woman’s hereditary preferences. They gathered resources locally, took care of their offspring, and waited for their mates to return with their hunting outcome.

“This may sound crazy,” Longman said, “but when a hunter is relatively fit the amount of energy they expend is actually tiny compared to the energy benefits of an antelope-sized animal, for example. Before the domestication of dogs, persistence hunting may have been one of the most efficient forms of hunting, and as a consequence may have shaped human evolution."

Source: Longman D. PLOS ONE. 2015.