NPR recently published a story examining the origins of omnivore diets in humans. Evolution indicates our early ancestors enjoyed a plant-based diet until approximately 2.3 million years ago. The anthropologist interviewed, Leslie Aiello, believes meat-consumption was a significant factor in the evolution of humans, specifically with brain size. She says, “You can’t have a large brain and big guts at the same time.” Indicating that digestion (of plant-based foods) consumed so much energy that no energy was left to devote to the brain. The brain requires twenty times more energy than muscle of the same mass.
The article goes on to discuss cooking. Cooking, in addition to releasing flavor in food and killing pathogens, also makes food more digestible which therefore makes much of the energy more available.
Despite the pleasant closing to the article which argues what really makes us human is our ability to cook which therefore provides opportunity for us to gather as families and communities, to share labor, and to enjoy conversation, this is the type of article that pits omnivores against vegetarians. (Try a Google search for “can meat make us smarter.”)
Aiello’s comment that you can’t have a big brain and a big stomach is perplexing. At first I thought perhaps our modern lifestyle makes such energy-dense foods such as meat obsolete (as a necessary part of our diet), but Aiello’s comment makes it sound that it is physically impossible to get enough energy to power our brains from plants alone. We know this isn’t true; there are plenty of smart, big-brained people in the world who consume a plant-based diet. Both their stomachs and their brains seem to get enough energy.
Is brain-size indicative of intelligence?
Even if it is assumed that Aiello is correct in attributing meat consumption to brain-size, this article doesn’t discuss how then (2.3 million years ago) relates to now. Is meat consumption necessary to sustain our brains now? Are calorically dense foods such as meat necessary when 68% percent of adult Americans are overweight and most lead sedentary lifestyles? How much meat was consumed by these early ancestors? Surely it was much less than today’s humans who have the benefit of agriculture (which began about 10,000 years ago) and the domestication of livestock (even more recent than agriculture.)
This article left me with more questions than answers.