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Was Meat the Original Brain Food?

  • Spence Cooper
  • August 19, 2010
Leslie Aiello in one of her discussions about the effects of meat to the brain.

Anthropologist Leslie Aiello, who runs a foundation that funds research in evolution, suggests our evolutionary ancestors’ switch to meat allowed the body to devote less energy to digestion and permitted growth in the brain.

Aiello argues that prior to consuming meat, our ancestors digested large amounts of fruits, nuts, roots, tubers, and berries, which required large stomachs. Aiello says that because nuts and berries have fewer calories and require lots of chewing and digestive work for the body to extract the nutrients, our ancestors spent a longer time eating.

Aiello believes the transition to high-fat and high-calorie meat allowed the body to invest more energy in brain growth, and the development of human tools — “the brain uses 20 times as much energy as the same weight in muscle.”

“You can’t have a large brain and big guts at the same time,”explains Aiello. “What we think is that this dietary change around 2.3 million years ago was one of the major significant factors in the evolution of our own species,”Aiello said.

Apparently the carnivorous change in humans was detected from the presence of a tapeworm found in wild dogs and then in early humans, indicating that at one time humans and hyenas fed on the same animal carcasses.

“If you look in your dog’s mouth and cat’s mouth, and open up your own mouth, our teeth are quite different,”said Aiello. “What allows us to do what a cat or dog can do are tools. Our teeth and jaws changed as tools made hunting and eating more efficient, because they weren’t needed to do as much grinding.”

Interesting theory, but Aiello’s hypotheses borders on junk science. First off, one of the key elements to the evolution and survival of our own species is that Homo sapiens were both herbivorous and carnivorous. Additionally, meat takes far longer, and requires much more energy to digest in the human body than nuts and berries. Man is omnivorous, but is structured physiologically more like herbivores.

Furthermore, nuts and berries require less digestive work for the body to extract nutrients than meat. Carnivores have comparatively short digestive systems (that are not required to break down cellulose found in plants), and digest meat much more efficiently, and at a faster rate (24-48 hours) than humans who may take weeks to fully digest meat.

And since human teeth, saliva, stomach acid, and intestines are more akin to other plant-eaters than carnivores, digesting meat is that much more taxing and energy intensive on the human body than nuts, leaves and berries.

Humans have up to twice the length of intestinal tracts than carnivores, so digested food must travel longer and further in the body. Meat passes quickly through a carnivore’s bowels which are smooth, and shaped like a pipe. Humans bowels, on the other hand, are bumpy, curvy and pouch-like. And since carnivores’ stomachs are roughly twenty times more acidic than human stomachs, it takes longer for meat to be broken down.

Humans “require dietary fiber to move food through their long and bumpy digestive tracts, to prevent the bowels from becoming clogged with rotting food”. Carnivores require no fiber.

Thus, for Aiello to conclude that our ancestors’ switch to meat allowed the body to devote less energy to digestion and permit growth in the brain, is a tenuous argument. Our ancestors didn’t switch to meat, our ancestors included meat as a dietary supplement in order to maximize and ensure survival. Granted, meat consumption may have afforded our ancestors more free time since meat is more satiating, but more energy is involved in digesting meat which can even temporarily deplete energy reserves in the short term. Think about how you felt the last time you ate a hearty steak dinner.

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