230Th/U Dating of Megafaunal Remains

长期以来，人们一直对人类在许多大洲的大型动物灭绝中所扮演的角色感兴趣，但如果没有精确的早期人类存在和大型动物灭绝前最后出现的证据，要解决这个问题往往是具有挑战性的。研究人员将致力于弄清人类最早到达一个大陆的时间和大型动物灭绝的时间。以前关于人类到达时间的学术研究使用了其他的年代测定技术，这些技术要么不适合我们感兴趣的时间间隔，要么需要难以验证的假设。这一研究主题也与过去人类对环境影响的一般问题有关：动物灭绝是否与自然气候变化或人类驱动的环境变化（如景观改造）及时相关？研究人员将进一步开发一种有前途的新方法，对大型鸟类蛋壳进行铀钍（U-Th）测年。在考古和古生物遗址中发现了已灭绝的不会飞的大型鸟类的化石和蛋壳。这种提出的新测年方法可能适用于过去50万年的历史，对于确定人类首次到达非洲大陆的考古遗址的年代尤其有用。利用U-Th测年，该项目旨在澄清早期人类到达和大型不会飞的鸟类灭绝的时间和速度，这些鸟类可能受到人类到达的影响，通过捕食和环境改变导致食物来源和/或栖息地的丧失。此外，这项工作的结果将与以前发表的其他环境变化记录相结合，从而可以更严格地评估人类到达与环境变化的关系。这些研究目标将整合本科生和研究生的训练。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

While there has been longstanding interest in the role humans play in large-bodied animal extinctions across many continents, it is often challenging to settle without precisely dated evidence of both early human presence and the last appearances of large animals prior to extinction. Researchers will undertake to clarify the earliest arrival of humans and the timing of extinctions of large animals on one continent. Previous scholarship on the timing of human arrival has utilized other dating techniques that are either poorly suited for the time interval of interest, or they require difficult-to-verify assumptions. This topic of research also relates to the general question of human impact on the environment in the past: do animal extinctions correlate in time with natural climatic changes, or human-driven environmental changes, such as landscape modification? Researchers will further develop a promising new approach to uranium-thorium (U-Th) dating of large avian eggshells. Fossils and eggshells of large extinct flightless birds, are found in archaeological and paleontological sites. The proposed new dating approach is potentially applicable over the past 500 thousand years and will be especially useful to date archaeological sites representing the time when humans first arrived on the continent. Using U-Th dating the project aims to clarify the timing and tempo of both early human arrival and the extinction of a large flightless bird, which may have been impacted by human arrival via predation and environmental modifications leading to loss of food sources and/or habitats. In addition, the results of this work will anchor other previously published records of environmental changes in time, allowing a more rigorous assessment of the relationship of human arrival to environmental changes. These research goals will integrate training of undergraduate and graduate students.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.