The 84th Annual Meeting of the American Association of Physical Anthropologists (2015)

The relative importance of adaptation versus genetic drift in driving diversification in Homo


Department of Archaeology, University of Cape Town

March 27, 2015 1:00, Grand Ballroom E/F/G Add to calendar

New fossil finds have fuelled the ongoing phylogenetic debate surrounding the evolution of early Homo, and highlight the remarkable variation and diversity present at the time of emergence of our genus. Previous interpretations of this diversity have focused on scenarios of adaptation, rarely considering the contributions of gene flow and genetic drift, or the possible roles of vicariance and dispersal. Understanding the action of these underlying processes on our lineage is an essential step in identifying probable evolutionary scenarios, and provides further evidence informing possible relationships between species. Here, we use statistical tests developed from quantitative genetic theory to test whether genetic drift (as opposed to selection) could be responsible for the cranial and mandibular variation observed in Homo. Analyses are performed on 3D scan data collected from early and later Homo specimens from eastern and southern Africa, Dmanisi, Georgia, as well as Java, Indonesia. Results indicate that in 90% of cases the cranial and mandibular phenotypic diversity seen between these geographical and spatially separated Homo groups is consistent with genetic drift. Rejections of drift, signifying possible selective forces, are associated with the Dmanisi hominins, as well as southern African early Homo, suggesting that these hominins at the latitudinal extremes of the early Homo range are adapting biologically to these different environments. This indicates that adaptation was important in the early migration of Homo out of Africa, and that geographically separate populations of Homo marshalled different responses (i.e. biological versus cultural) to environmental pressures.

This study was funded by the L.S.B. Leakey Foundation (Franklin Mosher Baldwin Fellowship), Palaeontological Scientific Trust (PAST), and South African National Research Foundation (NRF).