230Th/U Dating of Megafaunal Remains

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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.