Progress Daily

A study published in the Royal Society Journal Biology Letters suggests that brain size evolution may be driven by predator-prey relationships.

While there has been a consistent increase in relative brain size, and therefore intelligence, over most mammal groups throughout evolutionary time, predator-prey relationships have led to an intelligence divide, said lead researcher Susanne Shultz.

Shultz and colleague R.I.M. Dunbar studied data on animals from five forest communities in two continents. The animals came from Taï National Park in West Africa, the Ituri forest in the Republic of Congo, Mahale National Park in Tanzania, Kibale National Park in Uganda and Manu National Park in Peru.

The predators, which included leopards, chimpanzees, jaguars, pumas and other animals, were found to most often go for tinier brained prey, such as the small antelope, mongooses and the red river hog.

When the scientists ran all of the data through several statistical tests, they determined relative brain size was the most important predictor of biases in predator diets. Body size and prey group size were two other contributing factors, but nothing trumped brain size in predicting what a predator would choose for its dinner.

Shultz even believes humans may have been prey for so long that it added to our brainpower.

“As far as human evolution, coming out of the trees and onto the savannah entails high predation risk,” she explained. “It is possible that both living in large groups and living in risky environments both contributed to the increase in brain size seen in our ancestors.”

There are drawbacks to having a big brain.

“Large brains are extremely costly to both develop and maintain,” Shultz said. “They have high caloric demands.”

Larger-brained animals also tend to have slower development trajectories than smaller-brained critters, due to low reproductive rates, higher energy requirements and other factors.

Pea-Brains Make Best Prey, Study Finds,” by Jennifer Viegas

This entry was posted on Tuesday, August 22nd, 2006 at 4:59 pm and is filed under Cognition. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.