Collaborative Research: Comparative morphological analysis of the hand and wrist in Ardipithecus ramidus and Miocene hominoids

有440万年历史的化石物种Ardipithecus ramidus可能代表了人类最古老的祖先之一，它可能对人类和黑猩猩与他们最后的共同祖先的最初进化分化具有关键的洞察力。建立这种差异的原始条件(或“起点”)将对人类起源和进化生物学研究的几乎每一个方面产生变革性的影响。出乎意料的是，阿尔的骨架。拉米德斯被描述为与现存的类人猿的差异比预测的要大得多-相反，它与中新世早期更原始的类人猿相似。特别是，一些人认为，手和手腕保留了与谨慎攀登和手掌痉挛有关的特征(使用延长的手腕和承重的手掌，适合在树枝上方移动)。然而，许多解剖学还没有在严格的、定量的背景下进行检查，与中新世类人猿的比较也是有限的。该项目将对AR进行分析。Rmidus和现存灵长类和化石物种的广泛比较样本，使用三维(3D)形态计量学来验证以下假设：1)Ar。雷米德斯的手的使用方式与现存类人猿使用的高级垂直攀爬、悬挂和/或指关节行走的方式不一致；以及2)AR。拉米德斯是一种原始人(即与人类的关系比黑猩猩更近)。如果这些假设得到支持，那么原始人起源的模型就不能假设一个高度悬垂或关节行走的祖先，或者一个从事剧烈垂直攀登的祖先。因此，对许多人类适应的解释将不得不进行重大修改。大多数标本的所有度量数据和生成的3D数字模型将通过公共在线数据库获得，或提供给存放原始材料的博物馆。重要的是，3D模型记录了来自几个国内和国际机构的不可替代的化石和骨骼材料。该奖项支持职业生涯早期的科学家，包括一名亚裔美国人首席研究员(PI)，其中一名联合PI将促进美国和西班牙研究人员之间的合作。最后，该项目为学生提供了学习解剖成像和计算机建模技能的重要机会，这些技能在基础科学和生物医学中是不可或缺的。

The 4.4 million year old fossil species Ardipithecus ramidus may represent one of the oldest human ancestors, and it holds potentially critical insights into the initial evolutionary divergence of humans and chimpanzees from their last common ancestor. Establishing the primitive condition (or 'starting point') for that divergence would have transformative implications for nearly every aspect of research on human origins and evolutionary biology. Unexpectedly, the skeleton of Ar. ramidus has been described as differing from that of the living apes more than had been predicted - instead resembling that of more primitive apes from the early Miocene epoch. In particular, some have argued that the hand and wrist retain features related to cautious climbing and palmigrady (use of an extended wrist and weight-bearing palm, adapted for moving above branches). Much of the anatomy, however, has not been examined in a rigorous, quantitative context, and comparisons with Miocene apes have been limited. The project will analyze Ar. ramidus and a broad comparative sample of extant primates and fossil species using three- dimensional (3D) morphometrics to test the hypotheses that: 1) Ar. ramidus used its hands in a manner inconsistent with advanced vertical climbing, suspension, and/or knuckle-walking as used by living apes; and 2) Ar. ramidus is a hominin (i.e., more closely related to humans than chimpanzees). If these hypotheses are upheld, then models of hominin origins cannot assume a highly suspensory or knuckle- walking ancestor, or one that engaged in vigorous vertical climbing. Consequently, explanations for many human adaptations would have to be drastically modified. All metric data and the generated 3D digital models of most specimens will be available via a public online database or provided to museums housing the original material. Importantly, the 3D models constitute a record of irreplaceable fossils and skeletal material from several domestic and international institutions. This award supports early-career scientists, including one Asian American principal investigator (PI), and one of the co-PIs will foster collaboration between American and Spanish researchers. Finally, the project provides vital opportunities for students to learn skills in anatomical imaging and computer modeling, which are indispensable in the basic sciences and biomedicine.