The latest clue as to why our modern diet may be making us sick comes from Harvard primatologist Richard Wrangham, who argues that the biggest revolution in the human diet came not when we started to eat meat but when we learned to cook. Our human ancestors who began cooking sometime between 1.8 million and 400,000 years ago probably had more children who thrived, Wrangham says. Pounding and heating food “predigests” it, so our guts spend less energy breaking it down, absorb more than if the food were raw, and thus extract more fuel for our brains. “Cooking produces soft, energy-rich foods,” says Wrangham. Today we can’t survive on raw, unprocessed food alone, he says. We have evolved to depend upon cooked food.
To test his ideas, Wrangham and his students fed raw and cooked food to rats and mice. When I visited Wrangham’s lab at Harvard, his then graduate student, Rachel Carmody, opened the door of a small refrigerator to show me plastic bags filled with meat and sweet potatoes, some raw and some cooked. Mice raised on cooked foods gained 15 to 40 percent more weight than mice raised only on raw food.
If Wrangham is right, cooking not only gave early humans the energy they needed to build bigger brains but also helped them get more calories from food so that they could gain weight. In the modern context the flip side of his hypothesis is that we may be victims of our own success. We have gotten so good at processing foods that for the first time in human evolution, many humans are getting more calories than they burn in a day. “Rough breads have given way to Twinkies, apples to apple juice,” he writes. “We need to become more aware of the calorie-raising consequences of a highly processed diet.”
— Ann Gibbons in National Geographic on how our diets have evolved and whether returning to a “Stone Age diet” would help prevent high blood pressure, diabetes, and cardiovascular disease.