Geometric morphometric study of temporal variations in human crania excavated from the Himrin Basin and neighboring areas, northern Iraq

We performed three-dimensional analysis of the morphology of adult crania excavated from the Himrin basin and neighboring areas, northern Iraq, to investigate possible temporal variations in craniofacial shape in this area from the Chalcolithic and Bronze Age to the Islamic period. The sample comprised 45 specimens excavated by the Kokushikan University archeological expedition in 1978-1980 and now housed at Kyoto University, Japan. Computed tomography images of the crania were created and virtual models generated. Variability in cranial shape was examined using a geometric morphometric technique based on landmark coordinates. Ten modern Japanese adult crania were also included in the analysis for comparison. The results show that cranial shape in the pre-Islamic period was relatively dolichocranic, whereas those in the Islamic period were more diverse with both dolichocranic and brachycranic populations present, as suggested previously. Furthermore, the dolichocranic population tended to display relatively lower orbits and broader noses, and vice versa in the brachycranic population. However, the principal component classifying dolichocranic and brachycranic populations accounted for only about 12% of total variance, indicating that morphological variability of the crania is actually large and cannot be simply classified into two groups. A certain tendency of craniofacial variability was also found along a specific direction independent of temporal change, such directional variability was actually larger than variations through time. The Mesopotamian crania were found to differ from modern Japanese in terms of relative orthognathism of the maxilla and declination of the forehead. The present accurate description of craniofacial variability serves as a basis for future comparative research with neighboring populations towards understanding the origin and history of Mesopotamian inhabitants.