Distance running may have evolved as a desirable male trait: study

In the hunter-gatherer age, females likely judged potential mates by their ability to run, an indicator of being able to provide well.

Good providers, say the researchers, tend to be generous, and good hunters tend to be intelligent -- and both of these traits likely attracted more females, too.

"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," says lead author Dr. Danny Longman.

Born to hunt, lives to provide

The finding supports theories saying "persistence hunting," or, outwitting the prey by chasing it until it becomes exhausted, was commonly employed by our ancestors.

What's less clear is whether or not hunter-gatherers provided solely for their own families or shared their bounty within their tribe, as remaining tribes do.

In the latter case, there would be no need for females to seek out the fittest male to ensure a healthy, well-fed family, however, good hunters and providers are also desirable for their shared traits of intelligence and generosity.

Previous research says high exposure to the male sex hormone testosterone during one's time spent in the womb leads to evolutionary advantages for men including a high sperm count, strong sex drive and strong heart.

What his hands say about him

Working with the largest participant group of marathon runners of any study of its kind, the research team used the length of their fingers to gauge their level of exposure to testosterone during gestation.

A long wedding ring finger (the fourth finger from the thumb) by comparison to the index finger (which neighbors the thumb) has been scientifically proven to indicate high prenatal testosterone exposure.

Called the 2D:4D digit ratio, it's considered the most accurate way to tell if an adult was exposed to high levels of testosterone in the womb and also to gauge his potential for reproductive success.

The team assessed 542 runners of which 439 were men and 103 were women, photocopying their hands and noting their finish times at a local half marathon.

Of the men with favorable 2D:4D digit ratios, the top 10 percent of them were, on average, 24 minutes and 33 seconds faster than the 10 percent with the least favorable ratios.

Women also exhibited this correlation, although it was less pronounced among female participants, suggesting that running was more important for males from an evolutionary standpoint.