Meeting Abstract

96.1  Wednesday, Jan. 7  Male-Male Competition’s Influence on Primate Brain Size CUNNINGHAM, C. B.*; CARRIER, D. R.; Universtiy of Utah; University of Utah c.cunningham@utah.edu

Primates have evolved large brains. We hypothesized that male-male competition has helped drive the enlargement of the primate brain because competition demands extensive cognitive and physical interactions between opponents. Both the cognitive and physical aspects of physical competition should drive increases in brain size more in highly competitive primates than in less competitive primates. To address this prediction, we examined the correlation between brain size and both mass- and canine height-dimorphism, reliable indicators of male-male competition, within primates. Analyses were conducted with species and phylogenetically independent contrast (PIC) values. Consistent with the prediction, brain size was always positively correlated with mass- and canine-dimorphism using species values. Mass dimorphism was positively correlated with brain size using PIC values. Canine dimorphism was not correlated with brain size across the order. Further analysis of both indicators was done by breaking the order into the sub-groups: Strepsirhini, Haplorhini, New World Monkeys, Old World Monkeys, and Gibbons & Apes. Results were not consistent, and contained both significant positive and negative correlations between brain size and competition, using PIC values. In conclusion, brain size is weakly positively correlated with male-male competition overall, but this correlation is highly variable within specific sub-groups. This correlation is suggestive that competition has partially driven the increased brain size in primates.