Doctoral Dissertation Research: Postcranial Proportional Variation in Australopithecus

这项拟议研究的具体目标是使用一种新的方法评估原始人属南方古猿的物种边界。这将通过评估在Hadar、Sterkfontein和Makapansgat发现的化石组合中无关联个体的颅后骨骼比例的变化，并将其与所有现存的大型类人猿分类群进行比较来实现。由于物种是生物学和系统发育研究中最基本的单位，因此确定早期原始人化石记录中的物种边界对于所有其他涉及原始人生物学、进化和行为的分析至关重要。最近的发现和分析增加了原始人的变异量，其中一些被解释为表明不同物种之间存在不同的运动行为。对物种边界的准确评估比以往任何时候都更加重要，以便批判性地评估这些主张，追踪早期原始人的形态和行为变化的轨迹，并准确地估计选择作用于产生我们的人属的变异性。以前确定物种边界的尝试主要依赖于对头齿类遗骸的评估，往往产生相互矛盾的结果。然而，最近已经证明，颅后数据有效地反映了现存灵长类的分子系统学。不幸的是，早期的原始人化石记录主要是由许多个体的孤立骨骼元素组成的。通过组合可能来自不同个体的这些元素对，可以使用非参数密度估计来评估身体比例的变化。这种方法在其他领域得到了很好的应用，但从未被应用于古人类学问题。这将允许对后脑化石组合的彻底开发，并将对南方古猿的分类学和系统发育问题提供重要的启示。此外，这项研究不仅有望帮助厘清这些早期原始人的物种界限，还将显著有助于理解人类和类人猿颅后比例骨骼的变化。这项研究将产生几个广泛的影响。首先，它将促进学生的研究生培养。它还将开发一种研究变异性的新方法。第三，它将建立一种方法，为人类学的其他领域带来巨大的希望，在这些领域，人们希望从混合的骨骼组合中识别出单独的骨骼，例如在法医学和生物考古学中。

The specific objective of the proposed research is to evaluate species boundaries in the hominid genus Australopithecus using a novel method. This will be achieved by evaluating variation in postcranial skeletal proportions of unassociated individuals from the fossil assemblages recovered at Hadar, Sterkfontein, and Makapansgat, and comparing it to that seen in all extant large hominoid taxa. Because the species is the most fundamental unit in biological and phylogenetic studies, determining species boundaries in the early hominid fossil record is imperative to all other analyses involving hominid biology, evolution, and behavior. Recent discoveries and analyses have increased the perceived amount of variation in hominids, some of which has been interpreted as indicating divergent locomotor behaviors among species. Accurate assessment of species boundaries is more important than ever in order to critically evaluate these claims, to trace the trajectory of morphological and behavioral change among early hominids, and to accurately estimate the variability upon which selection acted to produce our genus, Homo. Previous attempts to determine species boundaries have relied primarily on the assessment of craniodental remains and have often produced conflicting results. Recently, however, it has been demonstrated that postcranial data validly reflect the molecular phylogeny of extant primates. Unfortunately, the early hominid fossil record is composed primarily of isolated skeletal elements from numerous individuals. By combining pairs of these elements from presumably different individuals, variation in body proportions can be assessed using nonparametric density estimation. This method is well established in other fields, but has never been applied to paleoanthropological problems. It will allow the thorough exploitation of the postcranial fossil assemblages and will shed significant light on questions of taxonomy and phylogeny in Australopithecus. Additionally, not only is this research expected to help clarify species boundaries in these early hominids, it will also significantly contribute to the understanding of both human and ape postcranial proportional skeletal variation.This research will have several broad impacts. First, it will advance the graduate training of the student. It will also develop a novel approach to studying variability. Third, it will establish a method that holds great promise for other areas of anthropology in which the recognition of individual skeletons from commingled skeletal assemblages is desired, such as in forensics and bioarchaeology.