The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)

Endocranial shape in early modern humans


Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology

Saturday 10:00-10:15, Grand Ballroom II Add to calendar

Humans have more globular brains and therefore endocasts than our extant and extinct relatives: chimpanzees and Neanderthals both have anterioposteriorly elongated endocasts. Based on an ontogenetic series of recent modern humans, we have previously shown that this modern human globular shape develops directly after birth during an ontogenetic phase that is absent in chimpanzees and Neanderthals. However, it is unclear at which point in the evolution of our species this unique pattern of brain development appeared.

Here, we aim to trace its evolutionary origin. Based on the shape of fossil adult humans, we investigate the morphological evolution of Homo sapiens endocasts using geometric morphometrics. Investigating representatives of H. sapiens from different time periods (comprising samples from Jebel Irhoud, Qafzeh, Skhul, Mladec, Cro Magnon) makes it possible to assess when and how (gradually or rapidly) this developmental phase appeared in the course of recent human evolution. As several relevant fossils are fragmentary and partly deformed, they require reconstruction before they can be analyzed. To this end, we generate and reconstruct virtual endocasts based on CT scans. We first use mirror-imaging and segmentation techniques, and then the thin-plate-spline interpolation function for reference-based reconstruction. Generating multiple reconstructions based on landmarks of 60 recent human endocasts, we keep track of the reconstruction uncertainty throughout the shape analysis. We document temporal trends of endocranial shape within anatomically modern humans during the Late Pleistocene and discuss potential implications for the evolution of the modern human brain.

Supported by EU FP6 Marie Curie Actions grant MRTN-CT-2005-019564 "EVAN" and by the Max Planck Society.

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