Mesowear study of ungulates from the early Pleistocene site of ‘Ubeidiya (Israel) and the implications for early Homo dispersal from Africa

Abstract

An ongoing question in Anthropology and Archaeology focuses on the role of climate change in human evolution and particularly in the dispersal of hominins out of Africa. One of the main hypothesis posits that early Pleistocene sites were open grassland habitats and that early Homo differentially inhabited such environments. Testing the environmental hypothesis requires robust paleoecological reconstructions of early Pleistocene ‘Out of Africa' sites. The early Pleistocene site of ‘Ubeidiya, central Jordan Valley, Israel, provides an excellent case study to test hypotheses regarding the role of climate in the dispersal of early Homo from Africa to Eurasia.Mesowear is a paleo-dietary proxy that measures facet development on selenodont ungulate molars. We analyzed the mesowear of five ‘Ubeidiya ungulate taxa averaged over all strata, then we analyzed the two ungulate taxa that had a large enough sample size for diachronic analysis: Equus tabeti and Dama sp. In both analyses, we used mesowear scores to predict percent grass in diet and precipitation in the habitat across a suite of modern taxa. We then use a phylogenetic generalized least squares (PGLS) framework to estimate these variables from the mesowear scores of the fossil taxa in ‘Ubeidiya. Phylogenetically-informed discriminant analysis (pFDA) was utilized to test the dietary categorical group identities of fossil specimens.Results suggests that percent graze in diet was lower in fossil taxa than in their modern counterparts while average precipitation was higher in the early Pleistocene than in the modern day locality of ‘Ubeidiya suggesting that overall ‘Ubeidiya was more humid with a close woodland forest that today.Results do not support the notion that ‘Ubeidiya was an open grassland habitat during the early Pleistocene and hominins did not preferentially occupy such environments. Thus it the adaptability of Homo to novel habitats out of Africa lend support to the climate variability hypothesis.