Why are primates big-brained? Researchers' answer is food for thought

March 27, 2017

Brain size in primates is predicted by diet, an analysis by a team of New York University anthropologists indicates. These results call into question "the social brain hypothesis," which has posited that humans and other primates are big-brained due to factors pertaining to sociality.

The findings, which appear in the journal Nature Ecology and Evolution, reinforce the notion that both human and non-human primate brain evolution may be driven by differences in feeding rather than in socialization.

"Are humans and other primates big-brained because of social pressures and the need to think about and track our social relationships, as some have argued?" asks James Higham, an assistant professor in NYU's Department of Anthropology and a co-author of the new analysis. "This has come to be the prevailing view, but our findings do not support it—in fact, our research points to other factors, namely diet."

"Complex foraging strategies, social structures, and cognitive abilities, are likely to have co-evolved throughout primate evolution," adds Alex DeCasien, an NYU doctoral candidate and lead author of the study. "However, if the question is: 'Which factor, diet or sociality, is more important when it comes to determining the brain size of primate species?' then our new examination suggests that factor is diet."

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Big Brains Are Pricey, Guppy Study Shows

Jan. 3, 2013 — Bigger brains can make animals, well, brainier, but that boost in brain size and ability comes at a price. That's according to new evidence reported on January 3rd in Current Biology, a Cell Press publication, in which researchers artificially selected guppies for large and small brain sizes.

The findings lend support to the notion that bigger brains and increased cognitive ability do go together, a topic that has been a matter of considerable debate in recent years, said Niclas Kolm of Uppsala University in Sweden. They also represent some of the first convincing evidence that large brains are expensive, evolutionarily speaking.

"We provide the first experimental evidence that evolving a larger brain really is costly in terms of both gut investment and, more importantly, reproductive output," Kolm said.

Together, the findings strongly support the idea that relative brain sizes among species are shaped through a balance between selection for increased cognitive ability and the costs of a big brain.

The results in guppies have important implications for us humans. After all, one of the most distinctive features of the human brain is its large size relative to the rest of the body.

"The human brain only makes up 2 percent of our total body mass but stands for 20 percent of our total energy demand," Kolm said. "It is a remarkably costly organ energetically."

Continued:  http://www.sciencedaily.com/releases/2013/01/130103131110.htm