Modern human origins in Australasia: Testing the predictions of competing models

The evolutionary background to the emergence of modern humans remains controversial. Four models have been proposed to explain this process and each has clearly definable and testable predictions about the geographical origins of early Australians and their possible biological interaction with other Pleistocene populations. The present study considers the phenetic affinities of early Australians from Kow Swamp (KS 1 and KS 5) and Keilor to Pleistocene Africans and Asians from calvarial dimensions. The study includes analyses employing log-transformed and size-corrected (Mosimann variables) data. The strongest signals to emerge are as follows: (1) a phenetic pattern in which Australians are most like each other, (2) all three crania possess a mosaic of archaic and modern features, (3) Kow Swamp crania also show strong affinities to archaic remains, (4) Keilor is more modern than KS 1 and KS 5 and (5) Keilor shows affinities to Pleistocene East Asian modern crania (Liujiang and Upper Cave 101) providing evidence for a broad regional morphology. The results refute the predictions of multi-species replacement models for early Australians but are consistent with single-species models. Combined with published evidence from DNA, the present study indicates that the Assimilation model presently offers the best explanation for the origins of Pleistocene Australians.