A newly published study says that the human brain mostly evolved in size and power over the past million years not because our hunter-gatherer ancestors ate meat, but rather because they ate high amounts of carbs, especially in the form of starch.
The research, published in the Quarterly Review of Biology, draws on a wealth of diverse data to discredit basic principles of the paleo diet, which advises would-be adherents to eat protein-heavy, low-carb diets — the same diet our evolving, more physically fit caveman ancestors supposedly ate during the Paleolithic era.
According to lead researcher Karen Hardy, from the Universitat Autònoma de Barcelona, and her team, the brain uses up to 25% of the body’s energy and up to 60% of its blood glucose — demands that are unlikely to have been met on a low-carbohydrate diet.
In addition, they say that low blood glucose levels resulting from pregnancy and lactation in mothers would have required high amounts of carbohydrates — available in the form of starch-rich seeds, fruits and nuts — in order for both the woman and child to be healthy.
Hardy and her team said that while raw starches are digested poorly in humans, cooking them breaks their crystalline structure and makes them much more easily digestible.
Co-researcher Les Copeland, from the University of Sydney, said:
“After cooking became widespread, starch digestion advanced and became the source of preformed dietary glucose that permitted the acceleration in brain size.
“In terms of energy supplied to an increasingly large brain, increased starch consumption may have provided a substantial evolutionary advantage.”
The researchers said that eating a diet similar to the one our ancestors ate during the Paleolithic era could be healthy as long as it included starchy foods grown underground such as potatoes and yams, as well as newer starchy grains like wheat, rye, barley, corn, oats and quinoa.
Co-researcher Jennie Brand-Miller, from the University of Sydney, summed up the research:
“It is clear that our physiology should be optimised to the diet we experienced in our evolutionary past.
“Eating meat may have kickstarted the evolution of bigger brains, but cooked starchy foods, together with more salivary amylase genes, made us smarter still.”