Doctoral Dissertation Improvement: Brain Size and Shape in Early Anthropoids

现存的类人灵长类动物--猴子、猿和人类--的大脑比狐猴和懒猴(Strepsirrhini)的大脑要大。大小的差异集中在大脑的某些区域，包括嗅球、新皮质和小脑。在讨论类人猿和链鼻龙对社会和环境压力的适应反应的差异时，经常会强调这些大小和比例的变化。大脑大小和形状的变化也可以用来解释现存灵长类动物头骨形状的一些差异。然而，这些比较分析中的大多数只基于对现存灵长类动物大脑的研究。化石证据表明，类人型分支之间的大脑大小平行增加，这为从比较和历史角度测试大脑大小和颅骨组织的发育和空间限制提供了宝贵的机会。灭绝的灵长类动物的脑大小和比例的许多细节可以从内隐形细胞的大小和比例中估计出来。通过对颅骨的微型CT扫描，虚拟地呈现了内播送。这项研究由杜克大学的博士生卡里·艾伦在理查德·凯博士的指导下进行，通过研究现存和灭绝的类人猿的虚拟内播来确定不同灵长类动物随着地质时间的变化趋势，探索了大脑大小、形状和比例的演变及其与颅骨形状的关系。三维几何技术被用来表征全球和区域内播形状的差异，这些差异可能携带功能或系统发育信号。重建的内胚层区域的大小和形状被用来评估小脑、大脑和额叶扩张的时机及其与颅形的关系。古生物数据集包括来自非洲和南美洲的早期类人猿化石，以及欧洲始新世的基础灵长类动物。这些新数据为检验大脑进化的适应性解释提供了有用的信息，这些解释是从对现存灵长类动物的比较研究中发展出来的。本科生培训将纳入研究活动，存档的、免费提供的灵长类活体显微CT扫描将作为教材。

Living anthropoid primates - monkeys, apes and humans - have proportionally larger brains than lemurs and lorises (Strepsirrhini). The size differences are concentrated in certain brain regions, including the olfactory bulb, neocortex, and cerebellum. These shifts in size and proportions are often highlighted in discussions of differences in adaptive responses to social and environmental pressures between anthropoids and strepsirrhines. Shifts in brain size and shape also are used to explain some differences in cranial shape among living primates. Most of these comparative analyses, however, are based only on studies of the brain of living primates. Fossil evidence for parallel brain size increase between anthropoid clades provides a valuable opportunity to test developmental and spatial constraints on brain size and cranial organization from both a comparative and historical perspective.Many details of brain size and proportions in extinct primates can be estimated from the size and proportions of endocasts, a cast of the internal braincase. Endocasts are virtually rendered using micro-CT scans of crania. This research, conducted by doctoral student Kari Allen, under supervision by Dr. Richard Kay at Duke University, explores the evolution of brain size, shape, and proportion, and its relationship to cranial form, by examining virtual endocasts of both living and extinct anthropoids to identify trends through geologic time in various primate groups. Three-dimensional geometric techniques are used to characterize global and regional differences in endocast shape that may carry a functional or phylogenetic signal. The reconstructed size and shape of selected regions of the endocasts are used to evaluate the timing of cerebellar, cerebral and frontal lobe expansion and their relationship to aspects of cranial form. The paleontological dataset includes early fossil anthropoids from Africa and South America, and European Eocene basal primates. These new data provide useful information to test adaptive explanations about brain evolution that were developed from comparative studies of living primates. Undergraduate student training will be incorporated into the research activities, and the archived, freely-available micro-CT scans of living primates will serve as teaching materials.