Early hominins and paleoenvironments: an integrated approach to exploring evolutionary processes

Zeresenay Alaemseged  - Max Planck Institute for Evolutionary Anthropology   

Abstract: Our understanding of the origin, diversification, and evolution of early hominin species is tightly linked to our knowledge of their paleobiology and the paleoecological context in which these processes took place. Addressing major issues related to the anatomy, behavior, diet and environments of these extinct taxa relies largely on the fossil evidence.  In this presentation I will explore how combining recently acquired field data with existing databases sheds fresh light on major questions in early hominin evolution.  First, I will show how a detailed analysis of data from the chronologically well-controlled Shungura Formation, in southwest Ethiopia, suggests that Australopithecus aethiopicus and Australopithecus boisei belong to a single evolving lineage.  This example of anagenic speciation is related to an important local environmental change at around 2.3 Ma. Second, I will show how integrating field data with techniques such as CT scanning helps to unravel questions pertaining to behavior, ontogeny, locomotor repertoire and paleoecology of early hominin species. Based on new fossil evidence some important questions related to the paleobiology of Australopithecus afarensis will be explored and put within the context of early hominin evolutionary scenarios. Finally, I will discuss how future research can help resolve the following questions: 1) Is there evidence of stasis in Australopithecus afarensis, or does the species show significant trends through time? 2) Is there evidence of geographic variation in A. afarensis as we compare the sample from Laetoli with contemporaneous intervals at Dikika? 3) Is there evidence of major environmental and faunal change during the 0.5 Ma that A. afarensis occurs in the Dikika-Hadar areas? 4) Did A. afarensis display a human or ape like juvenile body proportion, life history, brain growth rate and general ontogenetic trajectory? 5) Is the emergence of the genus Homo associated with directional environmental changes (e.g., the spread of grasslands), with periods of environmental variability, or with relatively stable habitats? 6) Finally, how can discoveries from Asbole contribute to a better understanding of the transition from H. erectus to H. sapiens and illuminate changes in the technological complex associated with this transition.