Journal
EVOLUTION
Volume 67, Issue 11, Pages 3339-3353Publisher
WILEY
DOI: 10.1111/evo.12197
Keywords
Brain size; body size; cetaceans; dolphins; encephalization; evolution; macroevolution; whales
Categories
Funding
- Biotechnology and Biological Sciences Research Council
- Royal Commission for the Exhibition of 1851
- National Science Foundation (NSF) [DEB 1025260]
- [NSF DEB 0640313]
- [NSF DEB 0743724]
- Direct For Biological Sciences [0743724] Funding Source: National Science Foundation
- Division Of Environmental Biology [0743724] Funding Source: National Science Foundation
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Cetaceans rival primates in brain size relative to body size and include species with the largest brains and biggest bodies to have ever evolved. Cetaceans are remarkably diverse, varying in both phenotypes by several orders of magnitude, with notable differences between the two extant suborders, Mysticeti and Odontoceti. We analyzed the evolutionary history of brain and body mass, and relative brain size measured by the encephalization quotient (EQ), using a data set of extinct and extant taxa to capture temporal variation in the mode and direction of evolution. Our results suggest that cetacean brain and body mass evolved under strong directional trends to increase through time, but decreases in EQ were widespread. Mysticetes have significantly lower EQs than odontocetes due to a shift in brain:body allometry following the divergence of the suborders, caused by rapid increases in body mass in Mysticeti and a period of body mass reduction in Odontoceti. The pattern in Cetacea contrasts with that in primates, which experienced strong trends to increase brain mass and relative brain size, but not body mass. We discuss what these analyses reveal about the convergent evolution of large brains, and highlight that until recently the most encephalized mammals were odontocetes, not primates.
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