How primates got big brains

March 29, 2017 12:00 am | Updated 04:12 am IST - New York

Fruit eating may be key to evolution of more grey matter, says study

Urban adventurer:A monkey feasts on figs in a leafy neighbourhood of New Delhi.V.V. KrishnanV_V_Krishnan

Urban adventurer:A monkey feasts on figs in a leafy neighbourhood of New Delhi.V.V. KrishnanV_V_Krishnan

Large brain sizes in primates may have been a result of their diverse diet, which included fruits and vegetables, rather than living complex social lives, scientists have found.

These results call into question “the social brain hypothesis,” which has posited that humans and primates are big-brained due to factors pertaining to social living.

The findings reinforce the notion that human and primate brain evolution may be driven by differences in feeding rather than in socialisation.

“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?” asked James Higham, an assistant professor at New York University (NYU).

“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,” he said.

“Complex foraging strategies, social structures, and cognitive abilities, are likely to have co-evolved throughout primate evolution,” said Alex DeCasien, an NYU doctoral candidate.

Diet may be key factor

“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,” he said.

Researchers, including Scott Williams, assistant professor of anthropology at NYU, examined more than 140 primate species — or more than three times as many as previous studies — and incorporated more recent evolutionary trees, or phylogenies.

They took into account food consumption across the studied species — folivores (leaves), frugivores (fruit), frugivores/folivores, and omnivores (addition of animal protein) — as well as several measures of sociality, such as group size, social system, and mating system.

Tougher to find

Results showed that brain size is predicted by diet rather than by the various measures of sociality — after controlling for body size and phylogeny.

Notably, frugivores and frugivore/folivores exhibit larger brains than folivores and, to a lesser extent, omnivores show significantly larger brains than folivores.

“Fruit is patchier in space and time in the environment, and the consumption of it often involves extraction from difficult-to-reach-places or protective skins,” said Mr. DeCasien.

“Together, these factors may lead to the need for relatively greater cognitive complexity and flexibility in frugivorous species,” he said.

The research was published in the journal Nature Ecology and Evolution .

Top News Today

Sign in to unlock member-only benefits!
  • Access 10 free stories every month
  • Save stories to read later
  • Access to comment on every story
  • Sign-up/manage your newsletter subscriptions with a single click
  • Get notified by email for early access to discounts & offers on our products
Sign in


Comments have to be in English, and in full sentences. They cannot be abusive or personal. Please abide by our community guidelines for posting your comments.

We have migrated to a new commenting platform. If you are already a registered user of The Hindu and logged in, you may continue to engage with our articles. If you do not have an account please register and login to post comments. Users can access their older comments by logging into their accounts on Vuukle.