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

国家科学基金会的支持将允许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：双足姿势的获得。人类进化的这一重要步骤可能发生在400万年前，但化石证据直到后来才被充分记录下来。大多数距今3.5-1.5万年的腿和手臂化石都是孤立的骨头，与被命名和鉴定灭绝物种的头骨和牙齿没有直接关系。塔尔曼女士将进行全面的分析，包括非相关的和相关的化石后颅骨遗骸，旨在解决关于非洲早期人类进化的一系列重要问题：1)是否存在特定的上新世-更新世人类物种的后颅骨特征？2)颅后特征的模式是否支持一种或多种基于颅骨遗骸的现有分类？3)关于上新世-更新世人族的运动能力，以及他们可能居住的生态位类型，颅后遗骸暗示了什么？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到目标样品的变形。将收集3.5 - 1.5 Ma期间的所有肱骨、桡骨、尺骨、股骨、胫骨、tali和跟骨化石的数据。这些数据将与许多现存的样本进行比较，包括：现代智人（7个不同的种群）、大猩猩、pygmaeus、类人猿（两个亚种-类人猿schweinfurthii和类人猿猿）和paniscus类人猿。首先将逐个元素分析数据，以在单个元素中寻找特定的形态模式。接下来，来自不同元素的数据将在一个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，功能性关节复合物和前肢和后肢形态的共变。在这两种情况下，将首先通过使用最大数量的标本和减少的里程碑集来进行单独的分析，其次通过集中在较少个体的特定解剖区域，但使用更全面的里程碑集来进行分析。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样本进行比较，以寻找差异程度和模式的相似性。判别函数分析将用于更好地评估种间差异。最后，将利用双块偏最小二乘分析来检查不同骨架元素之间的协变。这个项目的智力价值是三重的。首先，有大量未归属的颅后标本没有得到很好的研究。该项目旨在建立相关的颅后遗骸和分离元素之间的联系，以增加样本量，允许更可靠的统计分析，并对颅后存在的变异有更深入的了解。其次，许多其他研究都集中在对颅后骨骼的逐元素分析上；这个项目将把这些数据纳入分析，考虑到头盖骨在运动过程中协同工作的方式。最后，目前对人类颅骨后的研究大多使用传统的线性测量来收集数据。本研究将使用几何形态计量学作为描述和量化标本之间形状差异的方法。这个项目更广泛的影响主要是方法论上的。除了澄清早期人类的鉴定和适应的各个方面外，这个项目将提供一个适用于脊椎动物古生物学这一更广泛学科问题的方法的例子，并在国际上传播这种方法。这项研究促进了古人类学研究的国际联系和合作，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存入数据库，以便将来重新分析和研究；在这项研究中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。人类古生物学方面的工作成果具有广泛的公众利益，并将在技术和大众出版物中广泛传播。此外，对女博士生的支持将增加女性在科学领域的代表性。

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.