It’s not true that hunter-gatherers died young, before heart disease and the like could manifest themselves. Those who survived infancy could live to around 70. Granted they had infections and parasites, but even at old age, they apparently didn’t suffer from the chronic health conditions of affluent societies. Our Paleolithic cousins affirm the case, by counterexample, for the mismatch hypothesis, raising an obvious question: How might we become more like them? Using myself as a guinea pig, I submitted to Lieberman’s analysis to find out.
Back to Basics
In a course he teaches at Harvard, Lieberman collects exercise and dietary information from his students. The students compare themselves to tribal groups in Botswana, Tanzania and Paraguay who approximate the traditional hunter-gatherers. Sending him the same records and also my health information, I asked Lieberman where I fell on the spectrum between an average hunter-gatherer and the worst case. Also, how strong was the evidence that my health conditions, including serious illnesses I didn’t have but was at risk for, were caused by evolutionary mismatches?
First, the basics. At 6-foot-2 and 198 pounds with a body mass index (BMI) of 25.4, I was at the “edge of overweight,” Lieberman says. Although not obese, I was certainly heftier than a hunter-gatherer. One modern review of hunter-gatherer groups put their average BMI at 21.5, which health professionals consider low-normal. The lowest BMI provided by Lieberman, for female Bushmen (San people) in Botswana, was 18.2.
My systolic blood pressure (the pressure on arterial walls when the heart pumps), was 138, “a little on the high side,” he says, qualifying me for pre-hypertension in some diagnostic circles. In Bushmen and other foragers, systolic blood pressure ranges from 100 to 122, which is below normal in developed societies. At 67, I may merit a pass for my blood pressure since it usually trends upward with age, yet hunter-gathers my age aren’t ever hypertensive (systolic 140 or greater). According to field surveys, they don’t have atherosclerosis (hardening of the arteries), angina, electrocardiogram abnormalities or heart attacks, either.
“It’s also said they don’t get diabetes,” Lieberman adds, “but we don’t know. I say it’s extremely unlikely.” Insulin resistance, a harbinger of diabetes, seems “rare and nonexistent in foragers,” according to a 2007 paper by Boyd Eaton, Loren Cordain and Anthony Sebastian, experts on hunter-gatherer lifestyles. But, plucked from its formative environment, the hunter-gatherer is not immune to diabetes. Aborigines in Australia frequently become overweight and diabetic after they settle in urban areas. In the late ’70s, researcher Kerin O’Dea moved a study sample of Aborigines back to the bush for several weeks. Subsisting on lean kangaroo meat, fish and wild yams like their forbears, the Aborigines not only lost weight by foraging but also dramatically reduced their glucose levels and other metabolic signs of diabetes. Some were cured of the disease, at least temporarily.
Since there is no obesity, diabetes or heart disease in my corner, at least not yet, we turned to my less serious disorders that might be due to mismatches. Myopia? Nearsightedness is estimated to occur in just 3 percent of hunter-gatherers. “We know that in farming populations, it’s almost nonexistent, too,” Lieberman says. “I’d bet on that strongly as a mismatch.” If children are using their eyes in different ways today, we should get them outside more, he advises. What’s more, he suspects that eyeglasses are helping to keep genes for myopia prevalent in the human population. If so, that’s an example of dysevolution.
My lower back pain stems not just from my forebears who stood up and became bipeds. Back pain is a tricky condition, Lieberman notes, because the mismatch may entail both underuse and overuse. Hunter-gatherers may suffer from back pain (it hasn’t been assessed), but “we think they use their backs moderately,” he says. They don’t strain their backs like the farmers and factory workers who succeeded them, but they don’t sleep on soft mattresses and sit around in comfy chairs as we moderns do, either.