A Cranial Nonmetric Trait Investigation of Chalcolithic-Bronze Age Era Interactions across the Iranian Plateau

Methodological Protocols and Interaction Scenarios

Abstract

A battery of 32 cranial nonmetric traits were assessed among 436 adult individuals recovered
from nine Chalcolithic and Bronze Age archaeological contexts from the western, northern and southeastern peripheries of the Iranian Plateau. Three archaeologically based theoretical models of interactions across the plateau—the Neolithic food prodfuction, the Namazga expansion, and Bronze Age interregional interaction—were evaluated with four analytical models. In the first model all 32 traits were included. In the second model only those traits that differ across all nine samples at α< 0.05 were retained. In the third
model only those that met the alpha threshold with Bonferroni’s adjustment for multiple comparisons were included. In the fourth model, samples found not to differ from one another with the first three models were pooled and only those traits that met Holm’s (1979) nested rejective modification of Bonferroni’s adjustment were employed. Retained traits were assessed with correspondence analysis, neighbour-joining cluster analysis, and multidimensional scaling. Results indicate that the fourth method yielded the most
robust and non-volatile patterns of intersample affinities. None of the three reconstructions were supported in their entirety by the pattern of biodistance affinities obtained from cranial nonmetric trait frequencies. However, the biodistance patterns are most congruent with those expected with a population expansion across the Iranian Plateau during Neolithic era fueled by food production and animal husbandry that resulted in a pattern of interregional biological affinities dominated by long-standing bouts of in situ continuity. Some support is found for an overlay on this general pattern laid down in the Neolithic due to population growth and dispersal during the subsequent Namazga expansion, especially in southern Central Asia. In contrast, no support is provided forsignificant impacts due to Bronze Age interregional interactionps.