Elephant Molars as Archives of Environmental Seasonality in Hominin Paleoenvironments

DR. KEVIN T. UNO, then a graduate student at Columbia University, New York, New York, was awarded funding in October 2013 to aid research on 'Elephant Molars as Archives of Environmental Seasonality in Hominin Paleoenvironments.' Present day rainfall patterns in tropical Africa are highly variable. Rainfall shapes the landscape and defines the amount and types of vegetation available to animals as food. Seasonality of rainfall, defined as the frequency and amount that falls throughout the year, is particularly important. High amounts or continuous rainfall results in forests, whereas lower amounts and seasonal rainfall leads to wooded savannas and grasslands. Longstanding questions about seasonality in Africa include how it may have changed through time and how those changes may have affected the evolution of hominins. This study reconstructs rainfall seasonality during major transitions in hominin evolution from 4 to 1 million years ago (Ma) in the Lower Omo Valley, Ethiopia. The goal is to evaluate whether changes in seasonality occurred in conjunction with evolutionary events. The study uses oxygen isotope profiles in fossil elephant tooth enamel to reconstruct rainfall seasonality. Isotope in elephant teeth suggest a single annual rainy season was present from about 4 to 3 Ma, followed by decreased seasonality and the possible advent of two rainy seasons-as observed today in the region-around 2 Ma. Future work will focus on increasing the number of records of seasonality from teeth.