Dispersal of Homo sapiens around the Indian Ocean rim: a geometric morphometric study of craniofacial diversity.

Abstract

This thesis explores craniofacial diversity found in Homo sapiens around the Indian Ocean rim. Three dimensional landmark data, taken directly from the craniofacial skeleton, are examined in relation to the hypothesised southern dispersal route taken by Homo sapiens out of Africa during the Late Pleistocene. The thesis explores whether traces of this dispersal event are evident in the craniofacial morphology of modern human populations. It also explores further causes of morphological diversity between the populations. The first part of the thesis examines the patterns of craniofacial diversity found in samples from around the Indian Ocean rim. Biological and geographical distances are correlated and the results show that geography plays an important role in determining observed patterns of diversity. Distance from Africa is found to be statistically significant, suggesting that traces of the original Late Pleistocene dispersal remain today. Having determined geography as important in creating craniofacial diversity, the thesis additionally explores other potential causes of morphological variation. The results find that environmental conditions, including temperature and rainfall, are correlated with craniofacial shape. One finding of this initial section of the study is that there is considerable regional clustering of morphology in the samples from around the Indian Ocean rim. The second part of the thesis therefore examines dispersals within the identified regional clusters, including South and Southeast Asia, Melanesia and Australia. Craniofacial morphology is discussed in relation to proposed models of origin and evolution within these regions. Additionally, craniofacial variation within Polynesia is explored to provide a comparison of how diversity can develop over a relatively short period of time. The thesis concludes with a discussion of how craniofacial diversity is the result of a combination of multiple small founder effects and adaptation to local environmental conditions.