You know the deal by now: the Paleo diet is based on the premise that we should only eat what our cave-dwelling ancestors had immediate access to, like meat, fish, fruits, vegetables, and nuts. Starches and dairy, except in certain forms, are pretty much off the menu for even the least-strict Paleo adherents.
And while the discovery of the oldest human turd has revealed that our ancestors actually relied less on animal protein than we have generally come to believe, and that premodern humans likely processed and consumed barley and wheat during the Upper Paleolithic period, that hasn't stopped many of the food faddiest among us from eating only the burger between the bun.
But to those people, know this: The evolution of the human brain might have depended on those dreaded carbs.
That's the takeaway from a study published this month in the Quarterly Review of Biology, in which Dr. Karen Hardy and her research team argue that the growth of the human brain in the past 2 million years was not due only to the harnessing of fire and cooking of meat, as previously thought. We needed our starches, too.
Hardy et al. reviewed archaeological, genetic, and physiological data and conclude that "plant carbohydrates and meat were both necessary and complementary dietary components in hominin evolution."
Paleolithic humans certainly weren't biting into loaves of white bread, but they did get those carbs in the form of starchy roots and tubers, as well as from seeds and barks. In fact, the researchers argue that hunting may have been more of a status thing than one of necessity, and that "[although] meat may have been a preferred food, the energy expenditure required to obtain it may have been far greater than that used for collecting tubers from a reliable source."
Later on, with the advent of controlled fire for cooking, early humans were able to better digest those starches, which were poorly broken down by their digestive systems when raw. Not only that, our bodies evolved about a million years ago to start producing the enzyme amylase, which allows our mouths to start digesting starches as we're chewing—and helps make them more palatable.
According to Hardy, these two developments led to an increase of glucose in our diets, which not only helped us grow strong fetuses but enlarged the brains within them, and provided much-needed calories to lactating mothers. "Without cooking, the consumption of starch-rich plant foods is unlikely to have met the high demands for preformed glucose noted in modern humans," the study notes.
OK, OK, you're thinking. I don't give a good goddamn about enlarging my brain—I'm doing Paleo to have the most enviable clean-and-jerks in my CrossFit studio.
In that case, you still need energy! Think of your future fetuses, dear reader, and eat a sweet potato once and a while.