Dietary quality and encephalization in platyrrhine primates

Kari L. Allen, Richard F. Kay

Research output: Contribution to journalArticlepeer-review

36 Scopus citations


The high energetic costs of building and maintaining large brains are thought to constrain encephalization. The 'expensive-tissue hypothesis' (ETH) proposes that primates (especially humans) overcame this constraint through reduction of another metabolically expensive tissue, the gastrointestinal tract. Small guts characterize animals specializing on easily digestible diets. Thus, the hypothesis may be tested via the relationship between brain size and diet quality. Platyrrhine primates present an interesting test case, as they are more variably encephalized than other extant primate clades (excluding Hominoidea). We find a high degree of phylogenetic signal in the data for diet quality, endocranial volume and body size. Controlling for phylogenetic effects, we find no significant correlation between relative diet quality and relative endocranial volume. Thus, diet quality fails to account for differences in platyrrhine encephalization. One taxon, in particular, Brachyteles, violates predictions made by ETH in having a large brain and low-quality diet. Dietary reconstructions of stem platyrrhines further indicate that a relatively high-quality diet was probably in place prior to increases in encephalization. Therefore, it is unlikely that a shift in diet quality was a primary constraint release for encephalization in platyrrhines and, by extrapolation, humans.

Original languageEnglish
Pages (from-to)715-721
Number of pages7
JournalProceedings of the Royal Society B: Biological Sciences
Issue number1729
StatePublished - 2012


  • Expensive tissue
  • Human brain size evolution
  • New World monkeys
  • Phylogenetic comparative methods


Dive into the research topics of 'Dietary quality and encephalization in platyrrhine primates'. Together they form a unique fingerprint.

Cite this