Carlin Robinson, 12, walks from her grandmother’s car to the school bus in Manchester, Ky. Her house can be seen in the background. A study published in 2010, investigating high obesity rates in the town found that residents used cars to minimize walking distance, to the detriment of their health.

Photograph by Linda Davidson / The Washington Post via Getty Images.

If walking is a casualty of modern life the world over—the historian Joe Moran estimates, for instance, that in the last quarter century in the U.K., the amount of walking has declined by 25 percent—why then do Americans walk even less than people in other countries? Here we need to look not at pedometers, but at the odometer: We drive more than anyone else in the world. (Hence a joke: In America a pedestrian is someone who has just parked their car.) Statistics on walking are more elusive than those on driving, but from the latter one might infer the former: The National Household Travel Survey shows that the number of vehicle trips a person took and the miles they traveled per day rose from 2.32 trips and 20.64 miles in 1969 to 3.35 and 32.73 in 2001. More time spent driving means less time spent on other activities, including walking. And part of the reason we are driving more is that we are living farther from the places we need to go; to take just one measure, in1969, roughly half of all children lived a mile or more from their school; by 2001 three out of four did. During that same period, unsurprisingly, the rates of children walking to school dropped from roughly half to approximately 13 percent.

After the single session on the treadmill, the animals were allowed to rest and feed, and then their brain glycogen levels were studied. The food, it appeared, had gone directly to their heads; their brain levels of glycogen not only had been restored to what they had been before the workout, but had soared past that point, increasing by as much as a 60 percent in the frontal cortex and hippocampus and slightly less in other parts of the brain. The astrocytes had “overcompensated,” resulting in a kind of brain carbo-loading.

The levels, however, had dropped back to normal within about 24 hours.

That was not the case, though, if the animals continued to exercise. In those rats that ran for four weeks, the “supercompensation” became the new normal, with their baseline levels of glycogen showing substantial increases compared with the sedentary animals. The increases were especially notable in, again, those portions of the brain critical to learning and memory formation — the cortex and the hippocampus.

As if we needed another reason to exercise regularly.

They were investigating mild cognitive impairment (MCI), which can be an early sign of dementia.

Research, presented at a conference, claimed a high calorie diet was linked to having twice the risk of MCI, compared with a low calorie diet.

So poor memory means less working memory, working memory is a requirement of I.Q., low I.Q. makes you, well, less than you could be.

As if anyone needed more reasons to stop overeating and become healthy.

Seriously. Eating small amounts of mostly healthy food, combined with lots of light exercise and adequate sleep. It seems these are the keys to cognitive performance — not to mention longevity and overall health.

Über.

I suggest a different, even darker solution to the Paradox. Basically, I think the aliens don’t blow themselves up; they just get addicted to computer games. They forget to send radio signals or colonize space because they’re too busy with runaway consumerism and virtual-reality narcissism. They don’t need Sentinels to enslave them in a Matrix; they do it to themselves, just as we are doing today. Once they turn inwards to chase their shiny pennies of pleasure, they lose the cosmic plot. They become like a self-stimulating rat, pressing a bar to deliver electricity to its brain’s ventral tegmental area, which stimulates its nucleus accumbens to release dopamine, which feels…ever so good.

The fundamental problem is that an evolved mind must pay attention to indirect cues of biological fitness, rather than tracking fitness itself. This was a key insight of evolutionary psychology in the early 1990s; although evolution favors brains that tend to maximize fitness (as measured by numbers of great-grandkids), no brain has capacity enough to do so under every possible circumstance. Evolution simply could never have anticipated the novel environments, such as modern society, that our social primate would come to inhabit. That would be a computationally intractable problem, even for the new IBM Blue Gene/L supercomputer that runs 280 trillion operations per second. Even long-term weather prediction is easy when compared to fitness prediction. As a result, brains must evolve short-cuts: fitness-promoting tricks, cons, recipes and heuristics that work, on average, under ancestrally normal conditions.

The result is that we don’t seek reproductive success directly; we seek tasty foods that have tended to promote survival, and luscious mates who have tended to produce bright, healthy babies. The modern result? Fast food and pornography. Technology is fairly good at controlling external reality to promote real biological fitness, but it’s even better at delivering fake fitness—subjective cues of survival and reproduction without the real-world effects. Having real friends is so much more effort than watching Friends. Actually colonizing the galaxy would be so much harder than pretending to have done it when filming Star Wars or Serenity. The business of humanity has become entertainment, and entertainment is the business of feeding fake fitness cues to our brains.

Sobering.

Nevertheless, frenzied corporate cultures still confuse sleeplessness with vitality and high performance. An ambitious manager logs 80-hour work weeks, surviving on five or six hours of sleep a night and eight cups of coffee (the world’s second-most widely sold commodity, after oil) a day. A Wall Street trader goes to bed at 11 or midnight and wakes to his BlackBerry buzz at 2:30 am to track opening activity on the DAX. A road warrior lives out of a suitcase while traveling to Tokyo, St. Louis, Miami, and Zurich, conducting business in a cloud of caffeinated jet lag. A negotiator takes a red-eye flight, hops into a rental car, and zooms through an unfamiliar city to make a delicate M&A meeting at 8 in the morning.

People like this put themselves, their teams, their companies, and the general public in serious jeopardy, says Dr. Charles A. Czeisler, the Baldino Professor of Sleep Medicine at Harvard Medical School.¹ To him, encouraging a culture of sleepless machismo is worse than nonsensical; it is downright dangerous, and the antithesis of intelligent management. He notes that while corporations have all kinds of policies designed to prevent employee endangerment—rules against workplace smoking, drinking, drugs, sexual harassment, and so on—they sometimes push employees to the brink of self-destruction. Being “on” pretty much around the clock induces a level of impairment every bit as risky as intoxication.

As one of the world’s leading authorities on human sleep cycles and the biology of sleep and wakefulness, Dr. Czeisler understands the physiological bases of the sleep imperative better than almost anyone. His message to corporate leaders is simple: If you want to raise performance—both your own and your organization’s—you need to pay attention to this fundamental biological issue. In this edited interview with senior editor Bronwyn Fryer, Czeisler observes that top executives now have a critical responsibility to take sleeplessness seriously.

I wonder what America would look like if everyone got eight hours of sleep and got half an hour of exercise every day.