The theory behind the very trendy high-protein/low-carb Paleo diet is that we should mimic the diets of our Paleolithic ancestors, eating mainly meat, fish, and a restricted list of pre-agricultural vegetables and fruit. (There is some debate within the Paleo community about which starchy vegetables and how much of them are Paleo-approved, but most recommend limiting them if not barring them entirely.) But according to a new study in The Quarterly Review of Biology, the low-carb interpretation of the paleolithic menu is probably all wrong. The researchers posit that our cavemen and cavewoman ancestors loved—and needed—carbs as much as we do, even if they gathered them instead of cultivated them.
Based on a review of archaeological, genetic and physiological evidence, the researchers found that “plant carbohydrates and meat were both necessary and complementary dietary components” in the evolution of humans. Examination of 3-million-year-old teeth and the plant-life in the regions where our ancestors lived also signal that they were eating tubers and other starchy vegetables.
The root vegetables many modern Paleo dieters avoid likely played a key role in the original Paleo diet for a number of reasons. Because these plants grow underground, they were likely a key source of nutrition for our gathering forebears, who could dig them up as needed, the researchers say, and probably hunted much less than once thought.
“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,” the researchers write. (Worth noting: The researchers believe the tubers were collected by postmenopausal women, who shared them with the younger female relatives, which in turn, allowed them to have more babies. Men are not mentioned.)
Nutritional requirements and evolutionary evidence also support the idea that cavemen did not live on meat alone. As the brain grew during this period, more energy was needed, and it likely came from carbohydrates, not protein, too much of which can be toxic to the human body and even cause death.
This is further supported by evidence of two other major developments at the time: Saliva was evolving to better break down starch-rich plants, and our forebears were learning to cook. Both of these factors converged to make the vegetables tastier and easier to digest, providing the necessary energy for brain growth. These starchy plants also likely supported “improved reproductive functions,” including fetal growth and extra calories for lactating mothers.
The upshot? Paleo dieters, go eat some potatoes.