Darwin Made Me Fat
Even though many Americans say they don’t accept Darwin’s theory of evolution, it has become quite fashionable to blame our Stone-Age genes for the current American obesity epidemic. But we seem to have forgotten that we had the same Stone-Age genes 40 years ago when very few Americans were obese. And obesity rates are still quite low today in the same European countries which provided the genetic heritage for many of the Americans who are now struggling with overweight and obesity.
The idea that evolution is responsible for our expanding waistlines is appealingly simple and plausible. Calorie-rich sugar and fat were hard to come by during the Stone-Age, the period that encompasses 99 percent of the history of our species. And because we needed lots of calories, our brains naturally evolved to make us feel good when we made the effort to get some.
The richest source of sugar could be found in the nests of honey bees who were naturally reluctant to give it up. Even today, for Hadza hunter-gatherers in Tanzania, honey is by far the favorite food, and men suffer to bring home more of it when their wives are nursing. Juicy ripe fruits were the next most sugary foods, when we could manage to get to them before other animals, insects, molds, and yeasts. And the best source of fat was the meat, organs, and bone marrow of animals that had to be chased down, killed, butchered, and kept (or stolen away) from dangerous predators.
We needed lots of energy because of our big brains, the hallmark of human evolution. Brains are the most demanding organ in the body when it comes to both calories and fat. Because sugar and fat were both scarce and necessary, evolution programmed us to get as much as we could.