Dissertation Reseach: Determinants of Form in the Pubis of Middle/Late Pleistocene Anatomically Modern Humans and Neandertals

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The front portion of the birth canal (the superior ramus, or SPR) of the Neandertal pelvis differs from the modern human SPR in three ways: it is much longer, it is much thinner, and Neandertal males (not females) possess the longest SPR. These differences run contrary to what is expected, based on overall patterns of bony differences between Neandertals and modern humans. Many hypotheses accounting for the shape of the Neandertal SPR have been offered, but the biomechanical data needed to test them have been lacking. Four questions will be addressed by this study: 1) do the reported patterns of shape differences hold true in light of a fuller sampling of SPR of later hominids [Neandertals + modern humans]? 2) how much does the SPR vary in recent humans? 3) can any of the existing hypotheses for SPR vari-ation in later hominids be rejected or supported? 4) can the trunk torsion hypothesis, the only hypothesis to address all of the observed shape differences seen in the SPR of later hominids, be rejected or supported? Recent fossil discoveries have greatly increased the available number of SPR of later hominids, while the increased availability of CT scanners allows a more thorough analysis of internal SPR anatomy. This project will use CT scanners to gather the cross-sectional data needed for testing hypotheses of SPR function and variation. Nearly every pre-Holocene (older than 8,000 BC) Eurasian later hominid SPR will be examined, as will a large and diverse sample of recent humans in order to assess the modern range of SPR variation. The SPR plays a role in childbirth, locomotion, posture, and muscular force transmission between ab-domen and thigh. This project will help clarify the biomechanical role of the SPR in Neandertals, as well as the extent to which SPR differences between Neandertals and modern humans may be indicative of functional and behavioral differences.