Sitting on Your Ass Is Not What Evolution Intended

If only our human forebears and early ancestors could see us now. All that work they put into walking upright, building societies, growing giant cerebral cortices and learning to farm—all wasting away on the modern-day couch potato.

Natural selection seems to be taking its revenge. According to a Harvard study published this week in the British Journal of Sports Medicine, men who spend more than 20 hours a week watching television had a sperm count 44 percent lower than among men who didn’t watch any at all.

Exercise, on the other hand, greatly increased a man’s virility. To wit, men who moderately or vigorously exercised 15 or more hours a week had sperm counts 73 percent higher than men who exercised less than five hours a week.

No wonder we find in-shape bodies attractive. From a straight female’s perspective, at least, an in-shape guy is going to have an easier time fathering a child.

As an article in the Huffington Post notes, the sample size was small, which is important to bear in mind—just 189 healthy men between the ages of 18 and 22 who live in Rochester, N.Y. Still, as the article goes on to note, it bolsters the suggestions of some other recent research:

A Harvard School of Public Health study, published in March of last year, suggested that overweight men were "more likely" to generate less sperm, and that diminished sperm count could make conception difficult.

Furthermore, the Independent notes that the new research seems to jibe with with a study of 26,000 men that showed sperm counts plummeting 33 percent among men in the industrial world between 1989 and 2009.

But it’s just our sperm that suffers from our sedentary life. Its adverse effects on our weight (and, by proxy, our sense of mental well-being) are too obvious for further elucidation. And yet this new research calls to mind other recent findings that show just how good it is for our brains, not just our asses, to get off said asses.

Humans took over the world and invented amazing things like running water and the Rotato because of our outsized brains—three times larger, anthropologists say, than our size would otherwise suggest. Bears can swipe our heads off and eat us whole but we figured out how to shoot them first. That’s a big deal.

On that note, I like to think that when I’m at home watching a documentary like Grizzly Man I’m getting smarter. That may be true. But if I’m out exercising regularly, studies suggest, my brain actually generates new neurons—a phenomenon known as neurogenesis. As I’ve noted previously on Motherboard, research by Art Kramer, professor of psychology and neuroscience at the University of Illinois has documented such cases of neurogenesis in his experiments—a phenomenon that, as he notes, enhances cognition. That means if I exercise, I’ll probably do a better job understanding those documentaries when I watch them.

People also seem to think more creatively when we’ve been out in nature for a little while. As I noted in that same article:

For the study, psychologists from the Universities of Kansas and Utah teamed with Outward Bound, a wilderness expedition group, to organize multi-day wilderness hiking trips for 56 subjects, divided into eight separate groups sent to Alaska, Colorado, Maine and Washington. Subjects were not allowed to bring any forms of electronic technology, and groups had no association with one another.

Before the expeditions, roughly half of all participants were administered the Remote Associates Test, developed in the 1960s to measure complex cognitive activities like creative thinking and insight-based problem-solving. The other half were given the test while still in the wilderness after four days of hiking.

True to the experimenter’s predictions, subjects who took the test in the wilderness after four days performed better on their tests—by 50 percent.

The jury is still out regarding why humans developed such large brains. One theory holds it’s because we started cooking and eating meat. Others contend that natural selection favored our smarter, more sociable ancestors because communal living better ensured survival, thus growing our brains. (A recent and very controversial theory by evolutionary biologist, E.O. Wilson, suggests we were somehow genetically “spring-loaded” to be so social.)

And still another, provocatively suggests that our high endurance capacity for exercise helped make our brains larger. Kramer’s work on neurogenesis certainly doesn’t contradict that theory.

Regardless, it’s obvious that bigger, more creative brains have served us well so far. So has reproduction, upon which those larger brains were dependent in terms of natural selection. And that requires sperm. At the very least, it seems obvious that all this sitting around isn’t doing our brains, our sperm or the future of humanity any favors.