Active Low-Carber Forums - View Single Post - Has eating carbs decreased human brain-size?

Altari, interesting comparison with domesticated animals. One of the theories outlined in McAuliffe's Discover piece is "selection against aggression," a view promoted by Richard Wrangham:

Quote:

"Over the last 100,000 years language became sufficiently sophisticated that when you had some bully was a repeat offender, people got together and said, 'We've got to do something about Joe.' And they would make a calm, deliberate decision to kill Joe or expel him from the group -- the functional equivalent of executing him. [...] The story written in our bones is that we look more and more peaceful over the last 50,000 years."

Wrangham specifically points to the process of animal domestication, and the various phenotypic changes that occur during that process: more gracile features and a smaller cranial cavity, among other things.

To the point of the original post, however -- did agriculture shrink our brains? -- skeptics point out that neither Australians nor southern Africans experienced an agricultural revolution until quite recently, yet their brain size has been declining since the Stone Age as well.

To Martin's theory, minus the agriculture bit, David Geary (a cognitive scientist at the University of Missouri) says:

Quote:

"You may not want to hear this, but I think the best explanation for the decline in our brain size is the idiocracy theory." Geary is referring to the eponymous 2006 film by fMike Judge about an ordinary guy who becomes involved in a hibernation experiment at the dawn of the 21st century. When he wakes up 500 years later, he is easily the smartest person on the dumbed-down planet. "I think something a little bit like that happened to us," Geary says.

[...]

A recent study he conducted with a colleague, Drew Bailey, led Geary to his epiphany [...] Bailey and Geary found population density did indeed track closely with brain size, but in a surprising way. When population numbers were low, as was the case for most of our evolution, the cranium kept getting bigger. But as population went from sparse to dense in a given area, cranial size declined [...] The observation led the researchers to a radical conclusion: As complex societies emerged, the brain became smaller because people did not have to be as smart to stay alive. As Geary explains, individuals who would not have been able to survive by their wits alone could scrape by with the help of others -- supported, as it were, by the first safety nets.

So maybe you're onto something, Martin (although I think the large group theory may suffer from the same flaws as the agriculture theory -- does it explain universal brain shrinkage?).

On the other hand, University of Wisconsin anthropologist John Hawks thinks our shrinking brains may be a sign that we're getting smarter. Although streamlining the brain probably required some pretty rare mutations, he thinks that as human populations grew (and therefore the gene pool), the chances for such mutations to arise grew as well.