Hominin Dietary Niche Breadth Expansion during Pliocene Environmental Change in Eastern Africa

What caused early human ancestors to expand their diet to include many different kinds of plants? 

Chalachew Seyoum, an evolutionary anthropology doctoral candidate in the School of Human Evolution and Social Change and the Institute of Human Origins, will defend his dissertation proposal, "Hominin Dietary Niche Breadth Expansion during Pliocene Environmental Change in Eastern Africa."

His committee members are Professor William Kimbel (chair), President's Professor Kaye Reed (chair), Zeresenay Alemseged and Associate Professor Christipher Campisano.

Abstract

Consuming a wide variety of food resources (i.e., dietary generalization) is a central component of more recent hominin adaptations. However, it is still unclear why a wide dietary niche emerged during an early phase of hominin evolution. Stable-carbon isotope data from early Pliocene hominins Ardipithecus ramidus and Australopithecus anamensis have narrow, C3-dominated isotopic signatures. Conversely, mid-Pliocene Au. afarensis has a much wider isotopic distribution and consumed both C3 and C4 plants, indicating a transition to a broader dietary niche by around 3.5 million years ago.

The goal of Seyoum's project is to test the hypothesis that a mid-Pliocene spread of patchier and drier environments drove hominin taxa to expand their isotopic dietary niche breadth to include more C4 resources. To test this hypothesis, he is aiming to collect quantitative hypsodonty and qualitative mesowear data, proxies for rainfall and temperature seasonality, on fossil ungulate taxa. He will also record linear craniodental measurements (e.g., relative size of upper molars M2 and M3, premolar and molar row length, and mandibular corpus depth below M2) using digital calipers. These data will be analyzed using ecometric and ecomorphological approaches to reconstruct paleoenvironments of the associated faunas, and the results will serve as proxies to explore shifts in seasonality and other environmental variables at these sites in the 5.5–3.0 million years ago interval.

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