Function, Evolution and Anatomy Research Lab, Zoology Division, School of Environmental and Rural Science, University of New England, NSW 2351, Armidale, Australia.
Department of Neuroscience, Washington University School of Medicine in St Louis, MO, USA.
Proc Biol Sci. 2020 Jul 8;287(1930):20200807. doi: 10.1098/rspb.2020.0807.
Large brains are a defining feature of primates, as is a clear allometric trend between body mass and brain size. However, important questions on the macroevolution of brain shape in primates remain unanswered. Here we address two: (i), does the relationship between the brain size and its shape follow allometric trends and (ii), is this relationship consistent over evolutionary time? We employ three-dimensional geometric morphometrics and phylogenetic comparative methods to answer these questions, based on a large sample representing 151 species and most primate families. We found two distinct trends regarding the relationship between brain shape and brain size. Hominoidea and Cercopithecinae showed significant evolutionary allometry, whereas no allometric trends were discernible for Strepsirrhini, Colobinae or Platyrrhini. Furthermore, we found that in the taxa characterized by significant allometry, brain shape evolution accelerated, whereas for taxa in which such allometry was absent, the evolution of brain shape decelerated. We conclude that although primates in general are typically described as large-brained, strong allometric effects on brain shape are largely confined to the order's representatives that display more complex behavioural repertoires.
大脑体积较大是灵长类动物的一个显著特征，其身体质量与大脑体积之间也存在明显的异速生长趋势。然而，灵长类动物大脑形状的宏观进化仍存在一些重要问题尚未得到解答。在此，我们通过三维几何形态测量学和系统发育比较方法，基于代表 151 个物种和大多数灵长类科的大型样本，来回答以下两个问题：（i）大脑大小与形状之间的关系是否遵循异速生长趋势？（ii）这种关系是否在进化过程中保持一致？我们发现，大脑形状与大脑大小之间的关系存在两种截然不同的趋势。人科和长尾猴亚科表现出显著的进化异速生长，而在原猴亚目、丛猴科或阔鼻猴下目则没有发现这种趋势。此外，我们发现，在具有显著异速生长的分类单元中，大脑形状的进化速度加快，而在没有这种异速生长的分类单元中，大脑形状的进化速度则减慢。我们得出的结论是，尽管一般来说灵长类动物被描述为大脑较大，但强烈的异速生长效应对大脑形状的影响在很大程度上仅限于那些表现出更复杂行为组合的灵长类动物目代表。
