Collaborative Research: Hominin diversity, paleobiology, and behavior at the terminal Pliocene

250万年前到300万年前（Ma）这段时间一直被认为是人类进化中最关键的时期之一。在3.0 Ma，南方古猿的多个物种在非洲东部和南部的化石记录中得到了代表。到2.5 Ma，南方古猿大部分灭绝，取而代之的是进化出两个不同的谱系，对环境的适应性非常不同。一个谱系是我们自己的人属，其特征是大脑体积增大，并依赖于过去几百万年来持续存在的物质文化。另一个谱系，傍人，持续了超过100万年，并以三个物种为代表，具有独特的牙齿和面部适应性，可能会吃坚韧或坚硬的食物。尽管这段时间的重要性显而易见，但它在化石记录中的代表性很差，很少有化石标本被发现可以揭示这些谱系起源的原因和模式。Ledi-Geraru研究项目在一个包含这一重要时间间隔的多产地区开展工作，旨在阐明与南方古猿灭绝以及人属和傍人属出现有关的问题。研究人员将利用这项工作的结果，在公共科学宣传有关人类谱系，包括环境变化和人类适应之间的关键关系。该项目还将促进国际合作和学生培训。 在过去的十年中，研究人员已经确定了埃塞俄比亚阿法尔地区的含矿沉积物，其范围为2.9至2.4 Ma。从这些沉积物中发现的化石包括一个280万年前的下颌骨，这是已知的最早的人属代表，以及其他化石，表明该地区大约在同一时间存在多个人类物种。此外，Ledi-Geraru研究项目地区的几个地点显示，有证据表明古人类使用石器工具来获取动物组织和资源。在Ledi-Geraru项目现场将继续进行古人类学研究，以恢复更多的化石和考古材料，并更好地了解人类行为和环境背景之间的关系。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

The period of time between 2.5 to 3.0 million years ago (Ma) has long been considered one of the most critical in hominin evolution. At 3.0 Ma, multiple species of Australopithecus are represented in the fossil record across eastern and southern Africa. By 2.5 Ma, Australopithecus mostly died out, and in its place evolved two separate lineages with very different adaptations to the environment. One lineage is our own, Homo, characterized by a pattern of increased brain size and dependence on material culture that has persisted over the last several million years. The other lineage, Paranthropus, lasted over 1 million years, and was represented by three species with unique dental and facial adaptations for potentially eating tough or hard foods. Despite the obvious importance of this interval, it is poorly represented in the fossil record and few fossil specimens have been found that can shed light on the causes and patterns of the origins of these lineages. The Ledi-Geraru Research Project works in a fossiliferous region that includes this important time interval and aims to illuminate the issues relevant to the extinction of Australopithecus and the emergence of Homo and Paranthropus. The investigators will use the results of this work in public science outreach about the hominin lineage, including the critical relationship between environmental variance and hominin adaptations. The project also will foster international collaborations and student training. In the last decade, the investigators have identified fossiliferous sediments in the Afar region of Ethiopia that range from 2.9 to 2.4 Ma before present. Finds from these sediments include a 2.8 million year old mandible that is the earliest known representative of the genus Homo, and additional fossils suggesting that there were multiple hominin species existing at roughly the same time in the region. In addition, several localities in the Ledi-Geraru Research Project area show evidence that hominins were using stone tools to gain access to animal tissues and resources. Continued paleoanthropological research will be conducted at Ledi-Geraru Project sites to recover additional fossil and archaeological materials and better understand relationships between hominin behaviors and environmental contexts.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.