1Department of Anthropology, Indiana University, 2The Stone Age Institute, 3Department of Anthropology, Columbia University, 4Department of Anthropology/Archaeology and Applied Forensic Sciences, Mercyhurst University, 5Science and Engineering Library, Columbia University, 6Department of Anthropology, University of Wisconsin-Madison, 7Evolutionary Studies Institute and Centre of Excellence in PalaeoSciences, University of the Witwatersrand
April 21, 2017 9:30, Bissonet
There is no greater difference in frontal lobe morphology between apes and Homo sapiens than in the inferior frontal gyrus. The degree to which this evolutionary change is due to increase in brain size versus brain reorganization has long been in dispute. Here we show the Homo naledi DH3 fossil skull fragment, recently discovered in the Dinaledi chamber of the Rising Star cave system, South Africa, provides an endocast with an unusual degree of detailed cortical morphology that is essential to answering this question. In the ancestral morphology seen in apes and Australopithecus, the fronto-orbital sulcus forms the anterior boundary of the orbital cap, whereas the homologous sulcus in modern Homo has moved posteriorly and been draped over by the formation of the frontal opercula associated with Broca’s language area in humans. Despite an overall brain size similar to those of apes and australopithecines, H. naledi exhibits the modern condition of the orbital cap, bound anteriorly by an extended inferior frontal sulcus. In addition, a clear vertical ramus of the lateral fissure and its horizontal branch permits easy identification of a modern configuration of the frontal opercula. DH3 thus shows a modern Homo-like frontal brain organization despite its small size, which separates it from endocasts of A. africanus, A. afarensis, A. sediba, and H. floresiensis.
Funding for excavation and analysis was provided by the National Geographic Society, National Research Foundation of South Africa, and the Lyda Hill Foundation.