Expanding our horizons in understanding brain and dietary evolution in Primates and their kin

饮食的进化是灵长类起源过程的核心。所有关于灵长类起源的相互竞争的情景都有一个饮食成分：视觉捕食，重点是适应食虫；末端树枝觅食，涉及扩大树栖动物的饮食生态位，以包括更多水果；以及抓住跳跃假说，该假说纳入了灵长类早期进化到更大食草性的转变。饮食对于理解扩大而复杂的灵长类动物大脑的进化尤为重要。建立这样的大脑需要获得高能量的食物，而检索这种广泛分布和不规则可用的食物(例如水果)需要更大程度的处理能力。尽管对现代灵长类动物的分析支持饮食在大脑进化中的重要作用，但它们必然会将灵长类动物的起源简化为单个节点。化石记录表明，有许多干灵长类动物的谱系，这清楚地表明，故事比这类研究所暗示的理想化版本复杂得多。尽管近年来已经有了很大的进展，但仍有几个早期灵长类的谱系还没有做过量化工作来估计饮食的各个方面。这种不足的一个关键因素是，早期灵长类具有在现存灵长类中找不到的适应模式，这意味着该目中的活着成员不足以在这些群体中重建饮食。目前的研究将试图通过考虑更广泛的模式分类群和使用尖端的牙齿地形方法来填补其中的一些空白，从而实现牙齿形状的精确量化。这项研究还将寻求扩大可以收集的信息类型，并与灵长类动物大脑的早期进化进行比较。灵长类动物大脑大小进化中平行现象猖獗的有力证据表明，仅限于活着的类群的研究将受到限制，无法在所有灵长类动物的共同祖先中重建大脑的大小和形状。这突显了化石对于理解灵长类大脑进化早期阶段的重要性。由于大脑不会石化，即使保存最完好的化石，可获得的数据也仅限于保存在头盖骨内表面上的大脑印记(即内铸件)。目前的研究将寻求使用几何、形态测量和DiceCT方法来扩展可以从这种内广播中提取的关于改变形状和功能的信息。最终，这项研究的目标将是积累一个数据集，利用一个包含灵长类动物化石和现存成员以及密切相关群体的系统发育框架，综合考虑饮食变化与大脑大小和形状的变化(或不)。

The evolution of the diet is central to the process of primate origins. All of the competing scenarios for primate origins have a dietary component: visual predation focusing on adaptations for insectivory; terminal branch feeding involving an expansion of the arboreal dietary niche to include more fruit; and the grasp-leaping hypothesis, which incorporates a shift to greater herbivory in early primate evolution. Diet is of particular importance in understanding the evolution of the enlarged and complex primate brain. Building such a brain requires access to high energy food, while retrieving such broadly dispersed and irregularly available foodstuffs (e.g., fruit) requires greater degrees of processing power. Although analyses of modern primates have supported the important role of diet in brain evolution, they necessarily simplify the origin of primates down to a single node. The fossil record demonstrates that there were many lineages of stem primates, making it clear that the story is much more complex than the idealized version implied by such studies. Although there have been strides in recent years, there are still several lineages of early primates for which no quantitative work has been done to estimate aspects of diet. A critical component of this shortfall is that early primates have patterns of adaptations not found among living primates, meaning that living members of the order are insufficient models for reconstructing diet in those groups. The current study will seek to fill some of these gaps by considering a much broader range of model taxa and by using cutting edge dental topographic methods to allow for precise quantification of dental form. This study will also seek to expand the types of information that can be collected and compared with respect to the early evolution of the brain in primates. The strong evidence for rampant parallelism in primate brain size evolution implies that studies that are limited to living taxa will be constrained in reconstructing the size and shape of the brain in the common ancestor of all primates. This underscores the importance of fossils to an understanding of the early stages of primate brain evolution. Since the brain does not fossilize, the data available from even the best-preserved fossils is limited to the imprint of the brain preserved on the internal surface of the cranium (i.e., the endocast). The current study will seek to use geometric morphometric and DiceCT methods to expand the information about changing shape and function that can be extracted from such endocasts. Ultimately, the goal of this study will be to amass a dataset that will allow for a synthetic consideration of how shifting diets are aligned (or not) with changes in brain size and shape, using a phylogenetic framework that incorporates both fossil and extant members of Primates, and of closely related groups.