Dental microwear of bovids from the Pliocene-Pleistocene transition in the lower Awash Valley, Ethiopia

Abstract

Ethiopian fossil sites in the Lee Adoyta basin at Ledi-Geraru and the Maka'amitalu basin at Hadar straddle the Pliocene-Pleistocene transition and have both yielded fossil hominins attributed to early Homo. Faunal remains at these sites hold potential for providing insights into the ecological backdrop of the transition between these epochs in the lower Awash Valley and, by extension, the environments associated with the first appearance of Homo in the fossil record. Herbivore guild composition, ecomorphological study, and isotope analyses suggest that compared with paleoenvironments at earlier sites in the lower Awash, those in the Lee Adoyta basin and at Maka'amitalu had higher abundances of tropical grasses and sedges relative to browse plants. Here we bring another proxy to bear on the environments of the Lee Adoyta basin and Maka'amitalu associated with early Homo, dental microwear texture analysis. Dental microwear has been shown to separate grazing from browsing bovids and, because food choice reflects availability, can by extension provide insights into habitat. We employ texture analysis to infer the diets of bovid individuals from the Lee Adoyta basin (n = 13) and Maka'amitalu (n = 6) that preserve antemortem microwear. High-resolution replicas were scanned with a white-light confocal profiler and texture complexity and anisotropy were calculated for each surface and compared with baseline data for an extant sample of grazers, browsers, and mixed feeders. Values for bovids from the two sites do not differ from one another. Both samples have high anisotropy and low complexity, suggesting a graze-dominated diet and wide availability of grasses at both sites. These results are consistent with conclusions derived from other proxies.