The Cossack skull and a dihybrid origin of the Australian Aborigines

Abstract

Recent surveys of Australian prehistory^1–4 reveal the interest and debate surrounding the evolutionary implications of the observed range in cranial morphology of modern Australian Aborigines and their predecessors. In spite of an earlier model postulating a trihybrid origin^5,6, a theory favouring a homogeneous colonising stock had gained some acceptance^7,8. Discoveries^9,10 of the past decade raised doubts about the validity of the homogeneity concept and suggested an alternative two-population—gracile and robust—model^11–13. However, as all the material described was derived from a restricted area of South-East Australia, the possibility existed that the apparent dichotomy might reflect isolate variation or local adaptation¹⁴. We discuss here recently described human skeletal material from Cossack, Western Australia¹⁵ which has a demonstrable affinity with the postulated South-East Australian robust group, making local adaptation/population isolate explanations unlikely. The Cossack skull supports arguments favouring an early dihybrid origin with substantial change in Australian Aboriginal cranial morphology since the Pleistocene.