Hominids, geology, geochronology, and isotope ecology in the Omo-Turkana Basin, East Africa

人类的进化史引起了广泛的学术和公众的兴趣。东非的奥莫-图尔卡纳盆地包含了最连续的古人类地层序列，因此对古人类学具有特殊的重要性。这个盆地蕴藏着许多关于人类进化的基本问题的答案，但要把这些答案拼凑在一起，往往需要精确确定化石的年代和我们祖先的其他痕迹。该盆地记录了东非裂谷的火山喷发序列；这些灰烬的地球化学“指纹”可以识别出许多时间线，钾-氩定年法被用来确定许多这些灰烬的年龄，从而确定人类化石的年龄。盆地中广泛的暴露使得这些喷发的顺序得以确定；反过来，这些可以与东非的其他化石遗址相关联，并允许在特定的时间间隔内对遥远的遗址进行详细的比较。这项研究将对大量的骨灰进行排序，从而确定人类进化的详细历史。与这些灰烬一起的是记录气候和生态信息的土壤层；土壤碳酸盐的稳定同位素研究将允许对东非稀树草原生态系统的发展进行全面研究，并且可以在人类进化的背景下进行解释。奥莫-图尔卡纳盆地和埃塞俄比亚阿瓦什盆地的火山灰之间的详细相关性将允许对这两个地区的生态系统进行比较，以回答这两个地区的行为是否相同。对哺乳动物化石牙釉质的稳定同位素研究显示了饮食选择和某些食物的可用性；综合起来，它们可以用来确定过去400万年或更长时间内该地区的古干旱程度。因此，这项研究将使用火山灰的相关性，这些灰烬的年代测定和同位素研究来了解伴随人类进化的气候和生态变化。比较奥莫-图尔卡纳和阿瓦什地区的气候和生态事件将解决环境变化与人类进化之间关系的问题。人类进化的环境背景将被牢牢地置于适当的位置。该项目将为美国、肯尼亚和埃塞俄比亚的学生和科学家提供培训。将为至少8名研究生和16名本科生提供研究机会；这些本科生中的许多人将参加国际实地考察。未来教师的培训将从年度实地课程中进行；这些学生将来自美国各地的几所大学以及选定的外国机构。这个由美国、肯尼亚和埃塞俄比亚科学家参与的多国团队将加深他们之间的理解，并将提供一个未来科学家可以与之合作的骨干队伍。重要的是，只能在该领域有效传播的知识将被传递给至少三个不同国家的年轻科学家。最后，该项目将为非洲古生态学研究提供一个重要的同位素框架，并为420万年前至0.01万年前广泛分布的火山灰层提供一个数据库。

The evolutionary history of humans is of broad academic and public interest. The Omo-Turkana Basin in East Africa contains the most continuous sequence of hominin-bearing strata and is therefore of special importance to paleoanthropology. Within this basin lie many answers to fundamental questions about human evolution, but piecing together the answers often requires precise determination of dates of fossils and other traces of our ancestry.The basin has recorded the succession of volcanic eruptions in the East African Rift; geochemical "fingerprinting" of these ashes allows many time lines to be identified and potassium-argon dating is used to determine the ages of many of these ashes and hence of hominin fossils. The extensive exposures in the basin allows the order of these eruptions to be determined; in turn these can be correlated to other fossil sites in East Africa and allows distant sites to be compared in detail at certain time intervals. This study will then put in order the multitude of ashes that allow detailed histories of human evolution to be determined. Along with these ashes are soil horizons that record climate and ecological information; stable isotope studies of soil carbonates will allow a comprehensive study of the development of savanna ecosystems in East Africa and can be interpreted in the context of human evolution. The detailed correlations of volcanic ashes between sites in the Omo-Turkana Basin and the Awash Basin in Ethiopia will allow comparison of the ecosystems in the two regions to answer whether or not both regions were behaving in the same way. Stable isotopes studies of tooth enamel from fossil mammals shows the diet choices and availabilities of certain foods; taken together, they can be used to determine the paleo-aridity of the region over the last 4 million years or more. Thus, this study will use correlation of volcanic ashes, dating of those ashes, and isotope studies to understand the changes in climate and ecology that accompany human evolution. Comparison of climatic and ecologic events in the Omo-Turkana and Awash regions will address the problem of the relationship between environmental change and human evolution. The environmental context of human evolution will be put firmly in place.This project will provide training for American, Kenyan, and Ethiopian students and scientists. It will provide research opportunities for at least 8 graduate and 16 undergraduate students; many of these undergraduates will participate in international fieldwork. Training of future teachers will come about from the annual field course; these students will be from several universities from across the USA as well as from selected foreign institutions. This multi-national teamwork with participation of American, Kenyan, and Ethiopian scientists will deepen understanding between them, and will provide a cadre of individuals with whom future scientists can work. Importantly, knowledge that can only be effectively transmitted in the field will be passed on to younger scientists of at least three different nations. Finally, this project will provide an important isotopic framework for African studies of paleoecology, and a database of widespread volcanic ash layers over the time period from 4.2 to 0.01 million years ago.