Origins and biological affinities of the modern Thai population: An osteological perspective

The work focuses on the assessment of population affinities based on craniofacial skeletal data. The main objective is to test the "immigrant" and "endogenous" hypotheses for the origin of the modern Thai. The former proposes that the ancestors of the modern Thai migrated from China during the early second millennium A.D., and the latter proposes that the modern Thai are descended from prehistoric inhabitants of present-day Thailand. Although there is a great deal of research on East and Southeast Asia using archaeological, linguistic, and genetic data, detailed analysis of skeletal morphology has not been attempted beyond a few preliminary studies.Morphological comparisons among adult Thai and Chinese males and females, from both recent and archaeological populations, are made to assess biological distance among these groups. Both metric and discrete craniofacial traits are used. The compared features include fourteen metric traits: maximum cranial length, maximum cranial breadth, bizygomatic breadth, facial height, facial breadth, nasal height, nasal breadth, orbital height, orbital breadth, biorbital breadth, interorbital breadth, and three malar bone measurements (frontomalare orbitale to superior zygomaxillare, frontomalare orbitale to inferior zygomaxillare, and superior zygomaxillare to inferior zygomaxillare). Ten discrete traits are used, including metopic suture, nasofrontal suture, Os japonica, infraorbital suture, infraorbital foramen, incisura malaris, subnasal character, shovel-shaped incisor, four-cusped molar, and rocker jaw.Results of principal components analyses indicate that the craniofacial skeletal pattern changed through time. The early populations display larger craniofacial features than the modern sample population. Metric traits suggest that modern Thai are more closely related to archaeological Thai than to archaeological Chinese. Analysis of discrete traits, however, indicate that modern Thai and Chinese populations are very similar. Results of principal analyses also demonstrate that interorbital breadth is the best measure for differentiating these populations. Lastly, path analyses indicate that the primary ancestral groups for the modern Thai are not included in this study.U of I OnlyETDs are only available to UIUC Users without author permissio