Comparative analysis of encephalization in mammals reveals relaxed constraints on anthropoid primate and cetacean brain scaling

Bibliographic Collection: 
CARTA-Inspired Publication
Publication Type: Journal Article
Authors: Boddy, AM; McGowen, MR; Sherwood, CC; Grossman, LI; Goodman, M; Wildman, DE
Year of Publication: 2012
Journal: J Evol Biol
Volume: 25
Edition: 2012/03/23
Number: 5
Pagination: 981-94
Date Published: May
Publication Language: eng
ISBN Number: 1420-9101 (Electronic)10
Keywords: &, *Biological Evolution, *Phylogeny, Animals, Brain/anatomy, Cetacea/classification/*physiology, Cognition, Databases, Factual, Haplorhini/classification/*physiology, histology/*physiology, Organ Size/physiology, Species Specificity, Time Factors

There is a well-established allometric relationship between brain and body mass in mammals. Deviation of relatively increased brain size from this pattern appears to coincide with enhanced cognitive abilities. To examine whether there is a phylogenetic structure to such episodes of changes in encephalization across mammals, we used phylogenetic techniques to analyse brain mass, body mass and encephalization quotient (EQ) among 630 extant mammalian species. Among all mammals, anthropoid primates and odontocete cetaceans have significantly greater variance in EQ, suggesting that evolutionary constraints that result in a strict correlation between brain and body mass have independently become relaxed. Moreover, ancestral state reconstructions of absolute brain mass, body mass and EQ revealed patterns of increase and decrease in EQ within anthropoid primates and cetaceans. We propose both neutral drift and selective factors may have played a role in the evolution of brain-body allometry.


J Evol Biol. 2012 May;25(5):981-94. doi: 10.1111/j.1420-9101.2012.02491.x. Epub 2012 Mar 21.

Alternate Journal: Journal of evolutionary biology