Encephalization is not a universal macroevolutionary phenomenon in mammals but is associated with sociality
Open accessAbstract
Evolutionary encephalization, or increasing brain size relative to body size, is assumed to be a general phenomenon in mammals. However, despite extensive evidence for variation in both absolute and relative brain size in extant species, there have been no explicit tests of patterns of brain size change over evolutionary time. Instead, allometric relationships between brain size and body size have been used as a proxy for evolutionary change, despite the validity of this approach being widely questioned. Here we relate brain size to appearance time for 511 fossil and extant mammalian species to test for temporal changes in relative brain size over time. We show that there is wide variation across groups in encephalization slopes across groups and that encephalization is not universal in mammals. We also find that temporal changes in brain size are not associated with allometric relationships between brain and body size. Furthermore, encephalization trends are associated with sociality in extant species. These findings test a major underlying assumption about the pattern and process of mammalian brain evolution and highlight the role sociality may play in driving the evolution of large brains.
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The finding that mosaic changes contribute more to explaining neural system diversity across species than changes in relative brain size confirms that the traditional focus on relative brain size significantly underestimates the contribution of different neural pathways to primate neural system diversity.
“The finding that mosaic changes contribute more to explaining neural system diversity across species than changes in relative brain size confirms that the traditional focus on relative brain size [2,41–43] significantly underestimates the contribution of different neural pathways to primate neural system diversity.”
From Brain reorganization, not relative brain size, primarily characterizes anthropoid brain evolution (2013) · cites this paper as [41]
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- Authors
- Shultz, S., & Dunbar, R.
- Affiliations
- Kent State University (US)
- Corresponding author
- Shultz, Susanne
- Venue
- Proceedings of the National Academy of Sciences
- Publisher
- National Academy of Sciences
- Published
- 2010-11-22
- Volume
- 107
- Issue
- 50
- Pages
- 21582-21586
- ISSN
- 0027-8424 (ISSN-L)
- 1091-6490
- PMC
- PMC3003036
- OpenAlex
- W2169266697
- Cited by
- 238
- References
- 48
- Citations by year
- 2026: 6 · 2025: 8 · 2024: 10 · 2023: 9 · 2022: 21 · 2021: 12 · 2020: 5 · 2019: 8 · 2018: 17 · 2017: 19 · 2016: 16 · 2015: 19 · 2014: 22 · 2013: 15 · 2012: 40
- FWCI
- 14.83
- Type
- journal article
- Language
- en
- Open access
- green
- www.ncbi.nlm.nih.gov
- Locations
- Proceedings of the National Academy of Sciences (publishedVersion)
- Europe PMC (PubMed Central) (publishedVersion)
- PubMed Central (publishedVersion)
- PubMed (publishedVersion)
- Research Explorer (The University of Manchester) (submittedVersion)
- Funders
- British Academy
- Topics
- Physical Sciences › Earth and Planetary Sciences › Paleontology › Evolution and Paleontology Studies
- Social Sciences › Psychology › Social Psychology › Primate Behavior and Ecology
- Physical Sciences › Mathematics › Geometry and Topology › Morphological variations and asymmetry
- Keywords
- encephalization, brain size evolution, mammalian brain evolution, sociality, fossil mammals, social brain hypothesis, macroevolution
- MeSH terms
- Animals, Brain, Biological Evolution, Humans, Mammals, Organ Size, Phylogeny, Social Behavior, Body Size
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