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Review
. 2022 Dec;338(8):460-483.
doi: 10.1002/jez.b.23105. Epub 2021 Nov 23.

The mammalian brain under domestication: Discovering patterns after a century of old and new analyses

A M Balcarcel  1 , M Geiger  1 , M Clauss  2 , M R Sánchez-Villagra  1
Affiliations
Review

The mammalian brain under domestication: Discovering patterns after a century of old and new analyses

A M Balcarcel et al. J Exp Zool B Mol Dev Evol. 2022 Dec.

Abstract

Comparisons of wild and domestic populations have established brain reduction as one of the most consistent patterns correlated with domestication. Over a century of scholarly work has been devoted to this subject, and yet, new data continue to foster its debate. Current arguments, both for and against the validity of brain reduction occurring in domestic taxa, have repeatedly cited a small set of reviews on this subject. The original works, their sampling, methodological details, and nuances of results that would be key to establishing validity, particularly in light of new data, have not been investigated. To facilitate and encourage a more informed discussion, we present a comprehensive review of original brain reduction literature for four mammalian clades: Artiodactyla, Perissodactyla, Carnivora, and Glires. Among these are studies that generated the most cited brain reduction values in modern domestication literature. In doing so, we provide a fairer stage for the critique of traits associated with domestication. We conclude that while brain reduction magnitudes may contain error, empirical data collectively support the reduction in brain size and cranial capacity for domestic forms.

Keywords: Artiodactyla; allometry; encephalization; skull.

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Conflict of interest statement

The authors declare that there are no conflict of interests.

Figures

Figure 1
Figure 1
Graphical summary of brain size change between wild and domestic taxa here reviewed, and results of and newly analyzed data. For details and references see text and Table 1. Values should be interpreted while considering all caveats discussed in the main text for that group. Results of new analyses are in bold. Tree topology is based on Flynn et al. (2005) and Hassanin et al. (2012). Silhouettes credited to: phylopic.org; (aurochs) DFoidl (modified by T. Michael Keesey), (horse) Mercedes Yrayzoz (vectorized by T. Michael Keesey), (rat) Maija Karala, (gerbil) Flappiefh, and (rabbit) Anthony Caravaggi, https://creativecommons.org/licenses/by-sa/3.0/,https://creativecommons.org/licenses/by-nc-sa/3.0/,https://creativecommons.org/licenses/by/3.0/deed.de
Figure 2
Figure 2
Regressions of endocranial volume (EV) versus foramen magnum breadth (FM, as a proxy for body size) for the newly gathered data of wild and domestic (a, b)) South American camelids, (c) pigs, and (d) goats. EV estimated with “All‐Artiodactyla” formula from Finarelli (2011) based on cranial height, width, and length. Full analyses in Supporting Information file SD3. p‐values are for y‐intercept differences between wild and domestic regressions
See this image and copyright information in PMC

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