Horse vs. human

If you’re going to race against a horse, pick a hot day. That’s the basic conclusion of a recent analysis in the journal Experimental Physiology, which combed through more than half a century of data from three long-distance events where humans and horses race over the same course. But the findings also have deeper implications for how and why our ancestors started running in the first place.

Only the Man Versus Horse Marathon in Wales actually has people and horses racing head-to-head on the same day. Since its inception in 1980, humans have triumphed only twice, both times on hot days. (The first human winner, in 2004, was British runner Huw Lobb, who now lives in Montreal.) But data from the three races showed that the horses’ margin of victory tended to get narrower when race-day temperatures were higher. Horses may be faster, but they have more trouble dealing with the heat.

That finding is significant because the “born to run” theory of human evolution, advanced by Harvard anthropologist Daniel Lieberman and University of Utah biologist Dennis Bramble in 2004, posits that our ability to run prey to exhaustion across the hot savannah played a key role in shaping our subsequent evolution. Among our advantages: an unusual lack of fur that allows us to cool off by sweating copiously. Running long distances in hot weather is difficult for every species – but we’re better at it than most.

Alex Hutchinson is a Toronto journalist specializing in the science of running and other endurance sports.