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short—life expectancy at birth ranges between 20 and 40 years ...”), has to agree that, somehow, foragers managed to be healthier than agriculturalists: “Agriculturalists throughout the world were always less healthy than hunters and

gatherers.” The urban populations of Europe, he writes, “did not match the longevity of hunter-gatherers until the

mid-nineteenth or even twentieth century.”¹⁸

That’s in Europe. People living in Africa, most of Asia, and Latin America have still not regained the longevity typical of their ancestors and, thanks to chronic world poverty, global warming, and AIDS, it’s unlikely they will for the foreseeable future.

Once pathogens mutate into human populations from domesticated animals, they quickly migrate from one community to another. For these agents of disease, the initiation of global trade was a boon. Bubonic plague took the Silk Route to Europe. Smallpox and measles stowed away on ships headed for the New World, while syphilis appears to have hitched a ride back across the Atlantic, probably on Columbus’s first return voyage. Today, the Western world flutters into annual panics over avian flu scares emanating from the Far East. Ebola, SARS, flesh-eating bacteria, the H1N1 virus (swine flu), and innumerable pathogens yet to be named keep us all compulsively washing our hands.

While there were no doubt occasional outbreaks of infectious diseases in prehistory, it’s unlikely they spread far, even with high levels of sexual promiscuity. It would have been nearly impossible for pathogens to take hold in widely dispersed groups of foragers with infrequent contact between groups. The conditions necessary for devastating epidemics or pandemics just didn’t exist until the agricultural revolution. The claim that modern medicine and sanitation save us from infectious diseases that ravaged pre-agricultural people (something we hear often) is like arguing that seat belts and air bags protect us from car crashes that were fatal to our prehistoric ancestors.

If an infectious virus doesn’t get you, a stressed-out lifestyle and high-fat diet probably will. Cortisol, the hormone your body releases when under stress, is the strongest immunosuppressant known. In other words, nothing weakens our defenses against disease quite like stress.

Even something as seemingly unimportant as not getting enough sleep can have a dramatic effect on immunity. Sheldon Cohen and his colleagues studied the sleep habits of 153 healthy men and women for two weeks before putting them in quarantine and exposing them to rhinovirus, which causes the common cold. The less an individual slept, the more likely he or she was to come down with a cold. Those who slept less than seven hours per night were three times as likely to get sick.¹⁹

If you want to live long, sleep more and eat less. To date, the only demonstrably effective method for prolonging mammalian life is severe caloric reduction. When pathologist Roy Walford fed mice about half of what they wanted to eat, they lived about twice as long—the equivalent of 160 human years. They not only lived longer, but stayed fitter and smarter as well (as judged by—you guessed it—running through mazes). Follow-up studies on insects, dogs, monkeys, and humans have confirmed the benefits of going through life hungry. Intermittent fasting was associated with more than a 40 percent reduction in heart disease risk in a study of 448 people published in the American Journal of Cardiology reporting that “most diseases, including cancer, diabetes and even neurodegenerative illnesses, are forestalled” by caloric

reduction.²⁰

These studies lead to the slacker-friendly conclusion that in the ancestral environment, where our predecessors lived hand-to-mouth, a certain amount of dietary inconsistency—perhaps exacerbated by sheer laziness interrupted by regular aerobic exercise—would have been adaptive, even healthy. To put it another way, if you hunt or gather just enough low-fat food to forestall serious hunger pangs, and spend the rest of your time in low-stress activities such as telling stories by the fire, taking extended hammock-embraced naps, and playing with children, you’d be engaged in the optimal lifestyle for human longevity. ¹

Which brings us back to the eternal question asked by foragers offered the chance to join the “civilized” world and adopt farming: Why? Why work so hard when there are so many mongongo nuts in the world? Why stress over weeding the garden when there are “plenty fish, plenty fruits, and plenty birdies”?

We are here on Earth to fart around, and don’t let anybody tell you any different.

KURT VONNEGUT, JR.