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

  title={Comparative analysis of encephalization in mammals reveals relaxed constraints on anthropoid primate and cetacean brain scaling},
  author={Amy M. Boddy and Michael R. McGowen and Chet C. Sherwood and Lawrence I. Grossman and Morris Goodman and Derek E. Wildman},
  journal={Journal of Evolutionary Biology},
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… 

Breakdown of brain–body allometry and the encephalization of birds and mammals

It is proposed that avian and mammalian encephalization has been contingent on increased variability in brain growth patterns, and an exceptional pattern of brain–body allometry among birds and mammals is revealed, consistent with the hypothesis that they have relaxed allometric constraints compared to other jawed vertebrates.


It is suggested that cetacean brain and body mass evolved under strong directional trends to increase through time, but decreases in EQ were widespread, and that until recently the most encephalized mammals were odontocetes, not primates.

Exceptionally Steep Brain-Body Evolutionary Allometry Underlies the Unique Encephalization of Osteoglossiformes

  • M. Tsuboi
  • Biology, Psychology
    Brain, Behavior and Evolution
  • 2021
Examination of the relationship between static allometric parameters (intercepts and slopes) and evolutionary allometry revealed that the dramatic steepening of the evolutionary allometric slope in Osteoglossiformes was a combined result of evolution in the slopes and intercepts of static allometry.

Brain reorganization, not relative brain size, primarily characterizes anthropoid brain evolution

  • J. SmaersC. Soligo
  • Biology, Psychology
    Proceedings of the Royal Society B: Biological Sciences
  • 2013
Patterns of mosaic change in brain evolution are identified that mirror brain systems previously identified by electrophysiological and anatomical tract-tracing studies in non-human primates and functional connectivity MRI studies in humans and demonstrate deep evolutionary roots for mosaic patterns associated with motor control and learning.

Multivariate Meta-Analysis of Brain-Mass Correlations in Eutherian Mammals

It is concluded that Eutheria with either high AB or high EQ occupy positions at the top of the network of food chains (high trophic levels) based on correlations between these traits and measures of brain size.

Craniofacial Allometry is a Rule in Evolutionary Radiations of Placentals

If found in even more lineages of non-placental mammals, confirmed in birds, and possibly discovered in other tetrapods, CREA could become one of the most general rules of morphological evolution in land vertebrates.

Craniofacial Allometry is a Rule in Evolutionary Radiations of Placentals

If found in even more lineages of non-placental mammals, confirmed in birds, and possibly discovered in other tetrapods, CREA could become one of the most general rules of morphological evolution in land vertebrates.

Bigger Brains Led to Bigger Bodies?: The Correlated Evolution of Human Brain and Body Size

Results suggest that strong selection to increase brain size alone played a large role in both brain and body size increases throughout human evolution and may have been solely responsible for the major increase in both traits that occurred during the transition to Homo erectus.

Encephalization and longevity evolved in a correlated fashion in Euarchontoglires but not in other mammals

Evidence is found for the correlated evolution of encephalization and longevity, but only in some mammalian orders, among primates and rodents and their parent clade Euarchontoglires.

The allometry of brain size in mammals

A brain size dataset compiled from the literature for 1552 species with representation from 28 extant taxonomic orders is presented, showing strong phylogenetic signal as expected due to shared evolutionary histories.



Encephalization is not a universal macroevolutionary phenomenon in mammals but is associated with sociality

It is shown that there is wide variation across groups in encephalization slopes across groups and that encephalizations is not universal in mammals, and it is found that temporal changes in brain size are not associated with allometric relationships between brain and body size.

Trajectories and Constraints in Brain Evolution in Primates and Cetaceans

The comparative study on the trajectories through which the encephalization process has independently evolved in primates and cetaceans allows a critical appraisal of the causes, the time and the mode of quantitative and qualitative development of the brain in the authors' species and in the hominid evolutionary lineage.

Reconstructing the ups and downs of primate brain evolution: implications for adaptive hypotheses and Homo floresiensis

It is confirmed that brain expansion began early in primate evolution and shows that increases occurred in all major clades, and it is concluded that, while selection has acted to enlarge primate brains, in some lineages this trend has been reversed.

A Comparison of Encephalization between Odontocete Cetaceans and Anthropoid Primates

  • L. Marino
  • Psychology, Biology
    Brain, Behavior and Evolution
  • 1998
Results show that the encephalization level of Homo sapiens is still extraordinary relative to that of nonhuman species, but a subset of delphinid odontocetes are significantly more highly encephalized than the most highlyEncephalized anthropoid primates and narrow the gap in encephalizations between humans and nonhumans substantially.

Relative brain size and basal metabolic rate in terrestrial vertebrates

Re-examination of brain–body size relationships for large samples of species from three major vertebrate groups now shows that there is no empirical foundation for the concept of scaling to body surface area, and it seems that brain size may be linked to maternal metabolic turnover.

Primate brain evolution: Integrating comparative, neurophysiological, and ethological data

Recent work demonstrates the value of examining how evolutionary changes at different anatomical levels interrelate, and takes great care in the use of comparative methods and in finding multiple converging strands of comparative evidence.

Elephant brain Part I: Gross morphology, functions, comparative anatomy, and evolution

Dietary quality and encephalization in platyrrhine primates

  • K. AllenR. Kay
  • Biology
    Proceedings of the Royal Society B: Biological Sciences
  • 2011
Diet quality fails to account for differences in platyrrhine encephalization, and one taxon, Brachyteles, violates predictions made by ETH in having a large brain and low-quality diet.

Origin and evolution of large brains in toothed whales.

  • L. MarinoD. McSheaM. Uhen
  • Biology, Environmental Science
    The anatomical record. Part A, Discoveries in molecular, cellular, and evolutionary biology
  • 2004
It is shown that brain size increased significantly in two critical phases in the evolution of odontocetes, and was accompanied by a decrease in body size in Delphinoidea only by 15 million years ago.

Convergence of Complex Cognitive Abilities in Cetaceans and Primates

  • L. Marino
  • Biology, Psychology
    Brain, Behavior and Evolution
  • 2002
Evidence that convergent intelligence has occurred in two distantly related mammalian taxa is provided and these findings have important implications for understanding the generality and specificity of those processes that underlie cognition in different species and the nature of the evolution of intelligence.