By Jasminee Sahoye

A study by researchers at the University of Cambridge’s Division of Biological Anthropology shows that males with higher “reproductive potential” are better distance runners.

The study of marathon runners using finger length as a marker for hormone exposure shows that people who experienced higher testosterone in the womb are also better at distance running – a correlation particularly strong in men, although also present in women.

Researchers say the finding that males with greater “reproductive potential” from an evolutionary standpoint are better distance runners suggests that females may have selected men for athletic endurance when mating during our hunter-gatherer past, perhaps because of “persistence hunting”.

Distance running may also have acted as a positive signal for females of desirable male genetics more generally, say researchers. Good runners were likely to be better persistence hunters and consequently better providers.

“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,” said the study’s lead author Dr. Danny Longman.

Using the largest sample of marathon runners of any study of its kind, Longman and colleagues tested for specific finger lengths known as the 2D:4D digit ratio.

This digit ratio is the most accurate known way to tell if an adult was exposed to higher levels of testosterone as a fetus – a proven predictor of the “potential for reproductive success” in men, say researchers.

The team analysed 542 runners (439 men; 103 women) at the Robin Hood half marathon in Nottingham by photocopying hands and taking run times and other key details just after runners crossed the line.

They found that the 10% of men with the most masculine digit ratios were, on average, 24 minutes and 33 seconds faster than the 10% of men with the least masculine digit ratios.

The correlation was also found in women but was much more pronounced in men, suggesting a stronger evolutionary selection in men for running ability. The 10% of women with the most masculine digit ratios were, on average, 11 minutes and 59 seconds faster than the 10% with the least masculine.

Longman points out that prenatal testosterone exposure is a very small influence on running ability that doesn’t compete with training and muscle strength when it comes to performance but their unprecedentedly large sample size of over 500 people enabled the team to gather conclusive evidence.

“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.”

Persistence hunting is thought to have been one of the earliest forms of human hunting, evolving approximately two million years ago, said Longman.

And in a Northwestern Medicine study published in October 2013, it was found that men might be faster but women are stronger after researchers analyzed data from more than 400,000 runners who participated in 10 of the largest 10km (6.2 mile) races in the U.S. from as early as 2002 through 2011.

Other findings from that study include the top groups of men and women appear to be getting faster; the fastest men are increasingly younger; there are more sub-hour finishers with increasingly more women accomplishing this feat compared to men and an increasing percentage of finishers complete races in more than one hour.