title: Larger brain size indirectly increases vulnerability to extinction in mammals.
abstract: Although previous studies have addressed the question of why large brains evolved, we have limited understanding of potential beneficial or detrimental effects of enlarged brain size in the face of current threats. Using novel phylogenetic path analysis, we evaluated how brain size directly and indirectly, via its effects on life history and ecology, influences vulnerability to extinction across 474 mammalian species. We found that larger brains, controlling for body size, indirectly increase vulnerability to extinction by extending the gestation period, increasing weaning age, and limiting litter sizes. However, we found no evidence of direct, beneficial, or detrimental effects of brain size on vulnerability to extinction, even when we explicitly considered the different types of threats that lead to vulnerability. Order-specific analyses revealed qualitatively similar patterns for Carnivora and Artiodactyla. Interestingly, for Primates, we found that larger brain size was directly (and indirectly) associated with increased vulnerability to extinction. Our results indicate that under current conditions, the constraints on life history imposed by large brains outweigh the potential benefits, undermining the resilience of the studied mammals. Contrary to the selective forces that have favored increased brain size throughout evolutionary history, at present, larger brains have become a burden for mammals.
authors.affiliation: Conservation and Evolutionary Genetics Group, Department of Integrative Ecology, Estación Biológica de Doñana (EBD-CSIC), c/Américo Vespucio s/n, 41092, Sevilla, Spain. alejandro.gonzalez@iecologia.unam.mx.|Department of Zoology/Ethology, Stockholm University, Svante Arrheniusväg 18 B, SE-10691 Stockholm, Sweden. alejandro.gonzalez@iecologia.unam.mx.|Laboratorio de Conducta Animal, Instituto de Ecología, Circuito Exterior S/N, Universidad Nacional Autónoma de México, México, D. F., 04510, México. alejandro.gonzalez@iecologia.unam.mx.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Gonzalez-Voyer
authors.affiliation: Department of Conservation Biology, Estación Biológica de Doñana (EBD-CSIC), c/Américo Vespucio s/n, 41092 Sevilla, Spain. manuela.gonzalez@reading.ac.uk.|Ecology and Evolutionary Biology, School of Biological Sciences, University of Reading, Whiteknights, Reading, RG6 6AS, United Kingdom. manuela.gonzalez@reading.ac.uk.
authors.forename: Manuela
authors.initials: M
authors.lastname: González-Suárez
authors.affiliation: Conservation and Evolutionary Genetics Group, Department of Integrative Ecology, Estación Biológica de Doñana (EBD-CSIC), c/Américo Vespucio s/n, 41092, Sevilla, Spain.
authors.forename: Carles
authors.initials: C
authors.lastname: Vilà
authors.affiliation: Department of Conservation Biology, Estación Biológica de Doñana (EBD-CSIC), c/Américo Vespucio s/n, 41092 Sevilla, Spain.
authors.forename: Eloy
authors.initials: E
authors.lastname: Revilla
mesh_terms: D000818:Animals; D005075:Biological Evolution; D049628:Body Size; D001921:Brain / Q000033:anatomy & histology*; D053476:Extinction, Biological; D008322:Mammals / Q000033:anatomy & histology* / Q000502:physiology*; D009929:Organ Size
keywords: Body size allometry; IUCN Red List; extinction risk; life-history traits; phylogenetic path analysis