Postdoctoral Fellowship: EAR-PF: A seasonal-scale approach to African megafaunal extinction

Norwood, Alexandra Lynn, Ann Arbor MI

Investigators

Abstract

Over the last 50,000 years, many large mammals (over 45 kg) have gone extinct, which has greatly changed the Earth’s ecosystems. However, the causes of these losses in Africa have not been studied as much as extinctions in other parts of the world. Southern Africa has the best fossil record of these extinctions on the continent. Changes there in the timing and amount of rainfall during the year (rainfall seasonality) are thought to have contributed to the disappearance of several large plant-eating animals ~12,000 years ago. Because seasonality is difficult to figure out from the fossil record, these ideas have also been difficult to test. To address this problem, this project develops methods for studying seasonality in detail in the past. It then applies them to reconstruct changes in seasonality in southern Africa that happened around 12,000 years ago. Finding direct evidence of local seasonality will help us understand differences in seasonality across southern Africa at this time. That information will also give us environmental context for African extinctions at this time. This project will also support education and diversity in the geosciences by providing training and mentorship to underrepresented undergraduates and by engaging the public with paleobiology both in the USA and internationally. This project will test the hypothesis that late Quaternary extinctions in southern Africa are linked to increases in seasonality by (1) developing enamel serial sampling methodology for tracking seasonality in fossil ungulate teeth and (2) generating enamel isotope data to reconstruct changes in seasonality across the Pleistocene-Holocene transition in southern Africa. First, models of tooth development will be generated through histological analysis of molar growth in several ungulate taxa and serial enamel isotope analysis of modern teeth from those taxa will provide ground truthing for fossil applications. Then, following developed methods, fossil teeth will be serial sampled. The periodicities of their enamel isotope profiles will elucidate potentially shifting timing and intensity of precipitation across southern Africa from the terminal Pleistocene to early Holocene. This research addresses a high-profile question of global significance: what are the drivers of late Quaternary megafaunal extinctions? By addressing this question through a southern African case study, this project will amplify the presently understudied African record in global discussions and debates about the most dramatic extinction event of the Cenozoic. Additionally, the development of a more robust toolkit for measuring paleo-seasonality will be of broad interest to the geoscience community, with application to a broad range of questions and geographic 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.