Cox, Katherine, 2009. Human migration in prehistoric Northeast Thailand.

The aim of this thesis is to examine the scale of human migration in three prehistoric settlements in the Upper Mun River Valley (UMRV) Northeast Thailand, from c. 1700BC - AD500. Archaeological data implies migration may have had a central role in the development of agriculture and later metal technology in the region, which is suggested to show increased social complexity over this important stage in the development of states in mainland SoutheastAsia. The scale of these migrations, however, are not known and based on archaeological evidence it is unclear whether there were large numbers of individuals migrating into the region in order to bring about the changes seen in the archaeological record.

Two potentially complementary-methods are used to identify the extent of migration in the UMRV in this thesis. The first method, the study of dental morphological traits, is used as an indication of genotype of 78 prehistoric individuals. The second method is isotope analysis of the dental enamel of 74 individuals, used as indicators of childhood residence and diet. Strontium (Sr), Carbon (C) and Oxygen (O) isotopes are analysed. The first method reflects an individual's genetic heritage through inherited traits, while the second method is an indication of an individual's migration during their lifetime. Together, these methods may provide a powerful means to assess the scale of migration over an extended period of time in this region.

As it has been posited that the introduction of agriculture is related to migration of people into the region, the current study hypothesises that while immigrants would be identified from outside the UMRV during all phases of occupation at the sites, this would be particularly so during the earlier phases. It is also hypothesised through analysis of the morphological traits that genetic relationships at each site could be suggested. Finally, it is also hypothesised that individuals with evidence for infectious diseases, which are otherwise rare in the region, would be immigrants.

The frequencies of the dental morphological traits at each site are calculated, and a local pattern for each site developed. The results from the morphological traits suggest low levels of migration into the UMRV, and overall group homogeneity. Despite this homogeneity, it is suggested that several individuals may have been from a different genetic pool to others at the sites, reflected in a different combination of dental traits. There is also some evidence for genetic relationships between individuals, and over time, possibly indicating familial relationships at the sites.
Stability in the Sr isotopes over time suggest a local signature for the UMRV. Sr isotopes did not support a hypothesis of large-scale immigration into the UMRV, as there were few isotopic outliers identified. Those individuals with clear outlier Sr results, and therefore probable immigrants, were predominately female. All phases of occupation of the UMRV attracted some long-range inward movement of people, although the data suggests long-range migration diminished over time.
[delta]¹³C values show no significant change over time, possibly supporting the Sr data of limited migration into the region. While the interpretation of this isotope is primarily from a perspective of migration it is recognised that this may be limited to understanding variation in diet in the individuals.

[delta]¹O values show significant change over time (p = 0.00, ANOVA), perhaps consistent with previous research which suggested increased aridity in the UMRV. An alternative explanation of the [delta]¹O data is that migration increased with time, with people who were differentiated by their O isotopes but not their Sr, however the increased aridity hypothesis is favoured here.

The hypothesis that individuals with evidence for infectious disease would be long-range immigrants into the region is rejected. None of the individuals who had physical evidence for infectious disease had chemical data to support their being immigrants.

The putative migrants to the UMRV are presented as case studies, assessing the complementarity of the methods used. It is argued that given the changes in the environment over time in the UMRV the area may have become less attractive to immigrants and as a result the communities may have become more insular. The data yielded from the two methods have demonstrated the value of using inherited dental traits together with isotopic data of individual migration for investigating human mobility in the past. Using these methods, this study shows that there were low levels of migration into the UMRV and that long-range migration was more frequent in the earliest phases of occupation in the region.