Daniel E. Lieberman, professor of human evolutionary biology at Harvard The Story of the Human Body: Evolution, Health, and Disease (Pantheon)
"We’re well adapted by millions of years of evolution to be very efficient at making and storing fat," explains Lieberman. That’s because we desperately needed it: the average hunter-gatherer walked 9 to 15 miles a day. "It’s only in the last few generations that we have had access to as much energy as we want," he says. We can spend an entire day without ever raising our heart rate, while eating an excess of food—food high in sugars and fat. "Our bodies can’t cope with high levels of sugar in the absence of fiber. We don’t have the metabolism." This "mismatch" of our bodies to modern life results in a litany of new ailments, including obesity and diabetes.
Lieberman is not suggesting we return to a hunter-gatherer (aka Paleo) diet: "There is no single hunter-gatherer diet." In the Middle East, early people harvested wild barley to make flour; other foragers got most of their calories from fish. We can’t change our genes, Lieberman says, but we can keep them in mind, for example by limiting sugary foods and being more active.