Biological affinities and adaptations of Bronze Age Bactrians: IV. A craniometric investigation of Bactrian origins.

Discovery of a previously unknown Bronze Age civilization (Oxus civilization) centered on the oases of Central Asia revealed the presence of large, preplanned urban centers immediately above sterile soil. Given the absence of local antecedents, the sudden appearance and proliferation of these Oxus civilization urban centers in the oases of Bactria and Margiana immediately raised the issue of where the inhabitants of these urban centers came from. Three hypotheses have been offered by archaeologists to account for the origins of Oxus civilization populations. These include the early influence model, the late colonization model, and the trichotomy model. Eleven craniometric variables from 12 Aeneolithic and Bronze Age samples, encompassing 657 adults from Central Asia, Iran, and the Indus Valley, are compared to test which if any of these hypotheses are supported by the pattern of phenetic affinities possessed by the Oxus civilization inhabitants of the north Bactrian oasis. Craniometric differences between samples are compared with Mahalanobis generalized distance (d2), and patterns of phenetic affinity are assessed with two types of cluster analysis (WPGMA, neighbor-joining method), multidimensional scaling, and principal coordinates analysis. Results of this analysis provide no support for either the late colonization model or the trichotomy model but do offer some support for the early influence model. Nevertheless, it is clear that the early influence model fails to account for a shift in interregional contacts, perhaps from western China to the north around 2000 BC, that appears to have played a major role in the origins of the Oxus civilization inhabitants of the north Bactrian oasis.