DURHAM, N.C. -- Some primates have evolved big brains because their extra brainpower helps them live and reproduce longer, an advantage that outweighs the demands of extra years of growth and development they spend reaching adulthood, anthropologists from Duke University and the University of Zurich have concluded in a new study.
The four investigators compared key benchmarks in the development of 28 different primate species, ranging from humans living free of modern trappings in South American jungles to lemurs living in wild settings in Madagascar.
"This research focused specifically on the balance between the costs and benefits of growing a large brain," said Nancy Barrickman, a graduate student in Duke's Department of Biological Anthropology and Anatomy, who is first and corresponding author of a report now posted online for a future print edition of the Journal of Human Evolution.
"Growth rates are much slower in large-brained organisms, and that causes a delay in reproduction," Barrickman said. "If individuals wait too long to reach maturity then they run the risk of dying before they've had the chance to reproduce. So there must be some benefit to large brain size at the same time these costs are incurred.
"Is larger brain size causing life histories to become extended and slowed down? We think so," Barrickman added. "That obviously fits in very well with humans, who take forever to grow up and live a really long time. So we have the opportunity to have lots of offspring over that long period."
Barrickman drew these conclusions working with Carel van Schaik, a Duke adjunct professor on her doctoral studies committee who directs the University of Zurich's Anthropological Institute and Museum. Other coauthors include Duke graduate student Meredith Bastian, and Karin Isler, a collaborator of van Schaik's in Switzerland.
"Our main finding is that brain size is a far better predictor of the duration of im
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