The quantitative genetic analysis of craniometric phenotype of Yinxu population, Anyang

Abstract

Yin Ruins was the capital of the last phase of the Shang Dynasty (3250–2996 BP), which was located in the northwest of Anyang city in Henan Province, China. It is one of largest archeological sites in China famous for containing some of the earliest Chinese writing inscribed on oracle bones. A large number of human skeletons excavated from this site have also played an important role for understanding population structure and population history of the Yin Ruins and northern China. Previous researchers focused on the population structure of the Yin Ruins from the perspective of ethnology, and suggest that some skulls presented obvious differences in craniofacial morphology compared with the local population derived from the medium and small tombs (ZXM) and sacrifice pits (JSK). Yang stated that the JSK samples consisted of 5 different racial groups, such as Mongoloid, Caucasoid, Australoid and so forth. However, some scholars hold different views. This study analyzes the craniofacial shape variation of ZXM and JSK samples to explore their population history and population structure. A total of 212 adult skulls belonging to these 2 groups are analyzed in this article. The comparative data include 414 skulls from 9 sites in northern China whose absolute chronologies are close to that of Yin Ruins (4800–2000 BP). Multivariate exploratory (PCA) and evolutionary quantitative genetic method (R-matrix analysis) are used to study variance among populations, as well as population structure and population history. The result shows that: (1) Most of ZXM specimens have closer genetic distance with the late Neolithic population in local region, and there is a very frequent gene flow between the ZXM population and the residents of middle and lower reaches of the Yellow River. (2) The craniofacial morphological variation of JSK group is higher, and most of the JSK individuals have a closer genetic distance with the residents of middle and lower reaches of the Yellow River during the Xia and Shang Dynasty. In addition, this group also contained some individuals coming from the Inner Mongolia-Great Wall region, Ganqing region and regions outside this analysis. However, they do not have evidence of gene flow from Europe or Oceania. (3) In northern China, gene flow among populations is likely to be limited by geography during the Bronze Age, and there are also some differences in the level of gene flow among populations of different geographic units. Based on above results, the author suggest that the phenotypic variation among different populations is so large that the reliability of the ″use of racial classification to explore the extent of outside gene flow″ needs further confirmation.