UC Berkeley

The timing, location, and circumstances of the origin of anatomically modern humans has long been of interest, and ongoing studies continue to refine our understanding of early modern human evolution. However, research efforts are constrained by the available fossil evidence, which is predominantly comprised of geographically and chronologically disparate craniodental remains. Considering these limitations, new fossil evidence, particularly associated skeletons, is critically important to the study of modern human origins.

The Middle Awash research project has recovered a relatively complete early Homo sapiens partial skeleton (HAL-VP-9/1) from a Middle Stone Age archaeological context in the Halibee region of the Middle Awash study area of Ethiopia, preliminarily dated to ca. 54-106 ka. This dissertation includes the original description of the skeletal anatomy of this partial skeleton, as well as additional, more fragmentary hominid postcranial fossil material recovered from the same stratigraphic interval.

Understanding how Middle and Late Pleistocene hominid fossils relate to one another and to recent modern humans has been hindered by the sparseness of the Pleistocene fossil record, and by the variable combinations of plesiomorphic and derived traits displayed by the known fossil specimens. The chronological and geographic position of the Halibee fossils places them within a population ancestral or closely related to anatomically modern humans. These fossils therefore provide a lens through which we can examine the evolution of modern human anatomy.

The specific objectives of this dissertation include the qualitative and quantitative characterization of the skeletal anatomy of the Halibee fossils, via an assessment of the fossil morphologies relative to recent modern humans and our closest fossil relatives (particularly the Neanderthal lineage and other premodern sets of fossils). Accordingly, the Halibee fossils are described with reference to five recent modern human comparative samples and are systematically compared with fossils of Pleistocene Homo.

The morphologies exhibited by the Halibee fossils fall within the range of recent modern human variation in nearly all respects, albeit often near the margins of the range, but they do exceed the sampled range in a few features. The HAL-VP-9/1 partial skeleton, in particular, exceeds the sampled recent modern range in the absolute size of some elements, the sizes of articular surfaces, and the unusual proportions between the long bone ends and shaft cross- sectional sizes. Relative to other fossils of Pleistocene Homo, the Halibee fossils are similar to other early modern humans (i.e., Omo I, Skhul, and Qafzeh) in most respects, but exhibit several anatomical features that are more similar to the conditions described for Neanderthals.

The results of this dissertation contribute to our understanding of how early modern human anatomy varied and evolved. The anatomies preserved by the Halibee fossils reinforce previous calls to reconsider the polarity and dichotomy of traits historically treated as diagnostically modern human or Neanderthal. The results of this study also reinforce the need for better sampling of the Late and Middle Pleistocene African fossil record to better characterize the morphology ancestral to the modern human and Neanderthal lineages.

Given the relative scarcity of associated postcranial material in the African Pleistocene fossil record, the HAL-VP-9/1 partial skeleton constitutes a notable addition to the sample available for study. The Halibee fossils contribute to an emerging image of a morphologically heterogeneous segment of the modern human lineage in the Middle and Late Pleistocene of Africa. These fossils increase the available sample size for frequency-based anatomical studies that will be important for interpreting variation in the postcranial skeleton during the Middle Pleistocene, and consequently, for clearer insight into the evolution of modern humans.