You Were Born to Run (But Only When Forced To)

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And now, an evolutionary theory that provides a handy explanation as to why it can be so difficult to talk yourself into exercising. In Harvard Magazine, writer Jonathan Shaw summarizes the recent work of biologist Daniel Lieberman, who has studied the way natural selection has made people both natural-born endurance athletes and natural-born couch potatoes.

The modern human body is shaped for efficient running, what with our “shorter toes and heel bones, and the ability to cool off through sweating,” Shaw writes. And yet there also exists in us — so argues Lieberman — an innate laziness. Shaw explains:

Humans have also been selected to exercise only as much as they must to survive. The ancestors of modern humans lived as hunter-gatherers. In this subsistence lifestyle, food was often scarce, so resting was key to conserving energy for survival and reproduction. In other words, humans were born to run — but as little as possible.

Or, as Lieberman phrases it: “No hunter-gatherer goes out for a jog, just for the sake of it. … They go out to forage, they go out to work, but anything else would be unwise, not to mention maladaptive.” If it sometimes feels like you have to force yourself to go for a run — even if you truly enjoy it once you’re out the door — well, this helps explain why.

There are two ways to fight this, according to Lieberman. One idea: Make exercise fun by emphasizing the social aspect — pickup soccer, running groups, and the like. Another idea: Make exercise mandatory. The entire essay turns out to be a setup for Lieberman’s proposal to make physical education an academic requirement for Harvard students — who, for their part, often argue that they don’t have enough time. Lieberman isn’t hearing any of this. “[P]eople who get more physical activity have better concentration, their memories are better, they focus better,” he said. “So the time spent exercising is not time lost, but returned in spades.” How true that is, even if you sometimes have to force yourself to believe it.