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

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 and odontocete cetaceans have significantly greater variance in EQ, suggesting that evolutionary constraints that result in a strict correlation between brain and body mass have independently become relaxed. Moreover, ancestral state reconstructions of absolute brain mass, body mass and EQ revealed patterns of increase and decrease in EQ within anthropoid primates and cetaceans. We propose both neutral drift and selective factors may have played a role in the evolution of brain–body allometry.

哺乳动物的脑质量与体质量之间存在已被广泛证实的异速生长关系。相对脑尺寸偏离该模式的现象，往往与认知能力提升相伴出现。为探究跨哺乳动物类群的脑化程度变化事件是否存在系统发育结构，我们采用系统发育分析方法，对630种现存哺乳动物的脑质量、体质量以及脑化商数（encephalization quotient，EQ）开展了分析。在所有哺乳动物中，类人猿灵长类与齿鲸类（odontocete cetaceans）的脑化商数方差显著更高，这表明原本导致脑质量与体质量间严格相关性的进化约束已独立解除。此外，对绝对脑质量、体质量及脑化商数的祖先状态重建分析显示，类人猿灵长类与鲸类类群内部的脑化商数存在上升与下降的变化模式。我们提出，中性漂变与选择因素可能共同在脑-体异速生长的进化过程中发挥了作用。