DDI--Postcranial Variation in Plio-Pleistocene Hominins of Africa

NSF的支持将允许Melissa Tallman女士进行她的论文研究，研究人类起源研究中最有趣的问题之一：两足姿势的获得。人类进化的这一重要步骤可能发生在400万年前(Ma)，但化石证据直到更晚的时候才被很好地记录下来。大多数腿部和手臂的实际化石年代在3.5-1.5 Ma之间，是孤立的骨骼，与命名和识别灭绝物种的头骨和牙齿没有直接联系。塔尔曼女士将进行一项全面的分析，包括不相关的和相关的颅后化石遗骸，旨在解决关于非洲早期人类进化的一系列重要问题：1)特定的更新世人类物种是否具有颅后特征？2)颅后特征的模式是否支持基于颅骨遗骸的一个或多个现有分类？3)关于更新世人类的运动能力，以及它们可能居住的生态位类型，颅后遗骸意味着什么？这些问题将通过使用三维几何形态测量学(3D-GM)收集的数据来解决。在3D-GM中，数据以一组x、y、z坐标点(地标)的形式收集。与传统的线性测量相比，3D-GM的最大优点是保留了三维空间中测量之间的关系，并且可以将形状变化可视化为从参考样本到目标样本的变形。将收集距今3.5-1.5 Ma的所有肱骨、桡骨、尺骨、股骨、胫骨、距骨和跟骨化石的数据。这些数据将与一些现存的样本进行比较，包括：现代智人(七个不同种群)、大猩猩、侏儒大猩猩、轮叶大猩猩(两个亚种--P.T.schweinFurthii和P.T.、黑斑潜蝇(P.paniscus)。数据将首先逐个元素进行分析，以寻找单个元素中的特定形态模式。接下来，来自不同元素的数据将在更全面的分析中一起分析，该分析着眼于整个身体的形态模式，例如，功能性关节复合体以及前后肢形态的协变。在这两种情况下，首先将通过使用最大数量的样本和减少的地标集来执行单独的分析，然后通过在较少的个体中集中于特定的解剖区域来执行单独的分析，但使用更全面的地标集。这些数据将使用主成分分析和最小生成树进行探索。化石标本的数据可以与现存的样本进行比较，以寻找差异程度和模式的相似之处。判别函数分析将被用来更好地评估出租车之间的差异。最后，将使用两块偏最小二乘分析来检验不同骨骼元素之间的协变。这个项目的智力价值有三个方面。首先，有大量未归属的颅后标本尚未得到很好的研究。该项目试图在相关的颅后遗骸和孤立的元素之间建立联系，以增加样本规模，进行更有力的统计分析，并更深入地了解颅后遗骸中存在的差异。其次，许多其他研究集中于对后颅骨的元素进行分析；该项目将把这些数据纳入分析，考虑到颅后骨骼在运动过程中协同工作的方式。最后，目前对后脑人类的研究在很大程度上使用了传统的线性方法来收集数据。这项研究将使用几何形态计量学作为描述和量化样本之间形状差异的一种方法。这个项目的更广泛影响主要是方法论上的。除了澄清早期原始人的识别和适应方面的问题外，该项目还将提供适用于脊椎动物古生物学更广泛学科中问题的方法论范例，并在国际上传播这一方法。这项研究促进了古人类学研究中的国际联系和合作，古人类学研究越来越多地由多国团队进行。NYCEP几何形态计量学小组将小组成员收集的所有数据建立数据库，以供今后重新分析和研究；本研究收集的数据将被添加到该数据库中，并最终提供给同事使用。人类古生物学的工作成果引起了公众的广泛关注，并将在技术出版物和大众出版物中广泛传播。此外，对女性博士生的支持将增加女性在科学界的代表性。

NSF support will allow Ms. Melissa Tallman to undertake her dissertation research on one of the most interesting problems in the study of human origins: the acquisition of bipedal posture. This important step in human evolution probably occurred by 4 million years ago (Ma), but fossil evidence for it is not well-documented until somewhat later in time. Most of the actual fossils of the legs and arms dated between 3.5-1.5 Ma are isolated bones not directly associated with the skulls and teeth upon which extinct species are named and identified. Ms. Tallman will perform a comprehensive analysis including both unassociated and associated fossil postcranial remains designed to address a series of important questions regarding early human evolution in Africa: 1) Are there postcranial features that are characteristic of specific Plio-Pleistocene hominin species? 2) Does the pattern of postcranial traits support one or more of the current taxonomies based on cranial remains? 3) What do postcranial remains imply about the locomotor repertoires of Plio-Pleistocene hominins, and about the types of ecological niches they would have inhabited? These questions will be addressed with data collected using three-dimensional geometric morphometrics (3D-GM). In 3D-GM, data are collected as a group of x,y,z coordinate points (landmarks). The greatest advantages of 3D-GM as opposed to traditional linear measurements are that the relationships among measurements in three-dimensional space are retained, and shape changes can be visualized as deformations from a reference to a target specimen. Data will be collected on all fossil humeri, radii, ulnae, femora, tibiae, tali and calcanei dating from 3.5 - 1.5 Ma. These data will be compared to a number of extant samples, including: modern H. sapiens (seven different populations), G. gorilla, P. pygmaeus, P. troglodytes (two subspecies - P. t. schweinfurthii and P.t. troglodytes), and P. paniscus. Data will be analyzed first element by element, to look for specific morphological patterns in single elements. Next, data from different elements will be analyzed together in a more holistic analysis that looks at patterns of morphology across the entire body, e.g., covariation in functional joint complexes and in fore- and hind-limb morphology. In both cases, separate analyses will be performed first by using the maximum number of specimens and a reduced landmark set, and second by concentrating on specific anatomical areas in fewer individuals, but with a more comprehensive landmark set. The data will be explored using principal components analyses and minimum spanning trees. Data from the fossil specimens can be compared with the extant samples to look for similarities in the degree and patterning of differences. Discriminant function analyses will be used to better assess inter-taxic differences. Finally, two-block partial least squares analysis will be utilized to examine covariation between different skeletal elements. The intellectual merit in this project is threefold. First, there is a large number of unattributed postcranial specimens that have not been well studied. This project seeks to create linkages between associated postcranial remains and isolated elements, in order to increase the sample size and allow for more robust statistical analyses, as well as give greater insight into the variation present in postcrania. Second, many other studies have concentrated on element by element analyses of the postcranial skeleton; this project will incorporate these data into analyses that take into account the ways that the bones of the postcranium work together during locomotion. Finally, current studies of hominin postcrania have largely used traditional linear measures for data collection. This study will use geometric morphometrics as a way to describe and quantify shape differences between specimens. The broader impact of this project is mainly methodological. In addition to clarifying aspects of the identification and adaptation of early hominins, this project will provide an example of a methodology applicable to problems in the wider discipline of vertebrate paleontology and disseminate that method internationally. This study promotes international ties and collaboration in paleoanthropological research, which is increasingly conducted by multi-national teams. The NYCEP Geometric Morphometrics group databases all data collected by members of the group for future re-analysis and study; the data collected in this study will be added to that database and eventually made available for use by colleagues. The results of work in human paleontology are of broad public interest and will be widely disseminated in both technical and popular publications. Moreover, support of a female doctoral student will increase representation of women in science.