A revision of the Border Cave 1 cranium.

DERRICO, F.; BACKWELL, L.; BEAUDET, A.; WADLEY, L.

Virtual

Conferencia; Human Evolution - From Fossils to Ancient and Modern Genomes; 2021

Wellcome Genome Campus

Besides providing a unique archaeological assemblage that documents the early emergence of complex behavior in the human lineage [1], Border Cave (South Africa) is noteworthy for having yielded hominin remains of at least nine individuals, including the partial cranium Border Cave 1. While the exact provenance of Border Cave 1 is unknown, sequence stratigraphy and ESR dating converge towards an age from about 82 to 170 ka [2]. Accordingly, Border Cave 1 has the potential to play a key role in our understanding of the evolution and behavior of Homo sapiens. Here we present unreported information about the brain and bony labyrinth endocasts of Border Cave 1 and discuss related evolutionary implications.The Border Cave cranium was scanned at the microfocus X-ray tomography facility of the Palaeosciences Center at the University of the Witwatersrand (South Africa) at a spatial resolution of 117.4 µm (isotropic voxel size). Our comparative sample incorporates specimens of Early and Middle Pleistocene Homo as well as fossil and extant Homo sapiens. Both manual and automatic segmentation techniques were used to virtually reconstruct the brain and bony labyrinth endocasts. We applied a semi-automatic technique for detecting and identifying the vascular and sulcal imprints preserved on the inner surface of the braincase and we calculated labyrinth canal measurements as defined by Spoor [3] and Spoor and Zonneveld [4]. The overall morphology of the brain endocast approximates the globular shape of the modern human brain and differs from the long and low brain endocasts seen in the Middle Pleistocene fossil hominin species. The vascular imprints preserved on the right hemisphere indicate that the middle branch derives from the anterior branch, which is a pattern shared with Neanderthals and modern humans. The relative size and curvature of the semi-circular canals of the bony labyrinth conform to the ancestral configuration shared between Early and Late Pleistocene fossil hominins from Africa and the Levant, as well as modern humans. Collectively, our data thus provide further evidence about the cranial anatomy of Middle/Late Pleistocene humans in South Africa that will help better understanding fossil Homo sapiens biogeography, evolution, and behaviour.