Re-thinking the effects of body size on the study of brain size evolution

Font, E., García-Roa, R., Pincheira-Donoso, D. ORCID: 0000-0002-0050-6410 and Carazo, P., 2019. Re-thinking the effects of body size on the study of brain size evolution. Brain, Behavior and Evolution, 93 (4), pp. 182-195. ISSN 0006-8977

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Body size correlates with most structural and functional components of an organism’s phenotype – brain size being a prime example of allometric scaling with animal size. Therefore, comparative studies of brain evolution in vertebrates rely on controlling for the scaling effects of body size variation on brain size variation by calculating brain weight/body weight ratios. Differences in the brain size-body size relationship between taxa are usually interpreted as differences in selection acting on the brain or its components, while selection pressures acting on body size, which are among the most prevalent in nature, are rarely acknowledged, leading to conflicting and confusing conclusions. We address these problems by comparing brain-body relationships from across >1,000 species of birds and non-avian reptiles. Relative brain size in birds is often assumed to be 10 times larger than in reptiles of similar body size. We examine how differences in the specific gravity of body tissues and in body design (e.g. presence/absence of a tail or a dense shell) between these two groups can affect estimates of relative brain size. Using phylogenetic comparative analyses, we show that the gap in relative brain size between birds and reptiles has been grossly exaggerated. Our results highlight the need to take into account differences between taxa arising from selection pressures affecting body size and design, and call into the question the widespread misconception that reptile brains are small and incapable of supporting sophisticated behavior and cognition.

Item Type: Journal article
Publication Title: Brain, Behavior and Evolution
Creators: Font, E., García-Roa, R., Pincheira-Donoso, D. and Carazo, P.
Publisher: Karger
Date: November 2019
Volume: 93
Number: 4
ISSN: 0006-8977
Divisions: Schools > School of Science and Technology
Record created by: Jonathan Gallacher
Date Added: 20 Jun 2019 13:33
Last Modified: 06 Jul 2022 15:17

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