CORE Metadata, citation and similar papers at core.ac.uk Provided by Springer - Publisher Connector Invited Article Geology January 2013 Vol.58 No.3: 299306 doi: 10.1007/s11434-012-5459-6 SPECIAL TOPICS: Craniometrical evidence for population admixture between Eastern and Western Eurasians in Bronze Age southwest Xinjiang TAN JingZe1,2, LI LiMing1, ZHANG JianBo1, FU WenQing1, GUAN HaiJuan2, AO Xue2, WANG LingE1, WU XinHua3, HAN KangXin3, JIN Li1,2 & LI Hui1,2* 1 Key Laboratory of Contemporary Anthropology (Ministry of Education), School of Life Sciences, Fudan University, Shanghai 200433, China; 2 Shanghai Society of Anthropology, Shanghai 200433, China; 3 Institute of Archaeology, Chinese Academy of Social Sciences, Beijing 100710, China Received March 23, 2012; accepted May 11, 2012; published online October 11, 2012 Xinjiang, the most northwest provincial administrative area of China, was the area where the oriental people met the occidental. The populations in Xinjiang exhibit very high genetic diversity. Previous study revealed that the eastern Xinjiang populations of the Bronze Age were mixed by the Eastern and the Western Eurasians. However, few studies have been performed to reveal when the population admixture started and how far to the west it reached. In this paper, we studied 148 craniofacial traits of 18 skulls from the Bronze Age Liushui graveyard in Khotan (Keriya County) in the southwest of Xinjiang. Seventeen craniometrical pa- rameters of the Khotan samples were then compared with those of other ancient samples from around Xinjiang using dendrogram cluster analysis, principal components analysis, and multidimensional scaling. The results indicated that population sample of Liushui graveyard was mixed by the Western and Eastern Eurasians with about 79% contribution from the east. Therefore, we demonstrated that population admixture between east and west Eurasia can be traced back to as early as 1000 BC in southwest Xinjiang. craniometry, morphology, population admixture, Khotan Kingdom, Bronze Age Citation: Tan J Z, Li L M, Zhang J B, et al. Craniometrical evidence for population admixture between Eastern and Western Eurasians in Bronze Age southwest Xinjiang. Chin Sci Bull, 2012, 57: 299306, doi: 10.1007/s11434-012-5459-6 Xinjiang is the most northwest provincial administrative tral population deriving into populations in both sides. Ac- area of China, locating between East Asia and Central Asia. cording to the genomic analyses, the Xinjiang populations The modern populations of Xinjiang were found to have are not ancestor of the other Eurasian populations, but ad- both characters of Eastern and Western Eurasians since the mixed populations [6]. Therefore, our question is how early very beginning of the relevant anthropological studies [1]. the admixture happened, and where. Both physical anthropology [2] and molecular anthropology The early Xinjiang people were regarded as a different [3–5] revealed that indigenous Xinjiang people exhibit in- “race” from the East Asians by most central China ancient tergradations between the oriental and occidental people. people [7]. Archaeological findings revealed that Bronze Most populations are more similar to the oriental people Age residents of Xinjiang were very similar to the western genetically. Even the Uyghur, a population with the lowest Eurasians [8]. Therefore, it was widely accepted that the proportion of oriental genetic contribution, has at least 60% East Asians did not influence the early Xinjiang people lineages from the orient [5]. The characters of intergrada- much during the Bronze Age. However, recent studies of tions might have come from either of two processes: (1) the DNA from the Bronze Age Xinjiang Mummies led to admixture between two different populations, or (2) ances- very different conclusions. DNA analyses revealed pro- nounced eastern proportions in the genetic structures of the *Corresponding author (email: [email protected]) ancient mummies from several important archaeological © The Author(s) 2012. This article is published with open access at Springerlink.com csb.scichina.com www.springer.com/scp 300 Tan J Z, et al. Chin Sci Bull January (2013) Vol.58 No.3 sites in eastern Xinjiang, including Qumul [9], Kroran [10], Japan [16], and did not find them different from the interna- Charchan [11], etc. These results proved that the East tional standard. Asians had at least arrived in eastern Xinjiang at the Bronze Age. However, archaeological studies suggested that the 1.2 Clustering analyses ancient people of the western Xinjiang, the Saka, were dif- ferent nation from the eastern Xinjiang Tocharians [8]. The craniometrical results (17 indices) of Khotan were Therefore, the genetic admixture in western Xinjiang of the compared with those data from the Bronze Age samples Bronze Age is necessary to investigate. Recently, we stud- from Northwestern Asia, Central Asia [17,18], Xinjiang ied the cranial characters of a population sample of Bronze [19–28], and Central China [29–32]. Multidimensional Age Khotan Kingdom from Keriya County in southwest scaling analysis (MDS) and principal component analysis Xinjiang, and found apparent population admixture between (PCA) were used in population comparison. The first eight Eastern and Western Eurasians. principal components (94.2% of variance) were transformed This population sample was found in 2002 from a Bronze by Pearson’s r into genetic distances, and a dendrogram by Age graveyard near Liushui Villiage, Achan Township, Unweighted Pair Group Method with Arithmetic mean Keriya County, Hotan Prefecture, Xinjiang Uygur Autono- (UPGMA tree) was drawn based on these distances. As cra- mous Region, and was in the Silk Road (Figure 1). The ex- nial features show much more variations among male sam- cavation was finished in 2005. Fifty-two tombs were found. ples than among female samples, previous studies usually The human remains from the tombs were dated by 14C to only used data of males in clustering analyses. Our analyses 2950±50 year before present [12]. That is to say, this also compared males only. graveyard, the Liushui graveyard, is the oldest site found in southwest Xinjiang. 1.3 Admixture analysis We developed a method to explore the population structures 1 Materials and methods among our metric data. The method is to reveal the contri- bution rates of two presumed ancestral populations from 1.1 Samples and craniometrical standards Eastern and Western Eurasians to the Xinjiang populations We excavated 21 human skeletons from Liushui graveyard based on the mean values of 17 traits of each population. of Khotan in 2003. According to craniometrical standard, Eastern ancestral population is represented by ‘A1’ and they were 12 males, eight females, and one minor. Eighteen Western ‘A2’. Let Cit denote the mean values of the group i adults had intact skulls. We analyzed 31 observational fea- and the trait t in dataset, and i represent the contribution tures and 88 metrical items on these skulls, and calculated rate of A1 to group i as well as 1i to A2. The function of 29 morphologic indices (Table S1). We used the interna- residual error can be built tional standard of craniometry [13]. To compare our sample 30 17 to those from Central Asia and East Asia, we studied the 2 Residual error [CAit i 1 t 1i A 2 t ] , (1) craniometrical standards of Russia [14], China [15], and it11 Figure 1 Distribution of Khotan in Xinjiang and the archaeological cultures around. Tan J Z, et al. Chin Sci Bull January (2013) Vol.58 No.3 301 where A1t and A2t are the mean values of trait t of presumed ancestral populations A1 and A2, respectively. Note that both A1t and A2t are unknown and two group sets point to Eastern and Western Eurasians are distinct in our dataset, thus we let the mean of these two sets be the estimates of A1t and A2t, respectively. Our aim is that find the most possible set of i which minimize the function of residual error. Note that i is in- dependent to j for ij , the set of i has sole solution [(AC 2 ) ( AA 2 1 )] t titt t. (2) i (2AA 1)2 t tt The solution of the function above may be negative or greater than 1, and according to the property of the function, it should be corrected by letting negative value to be 0 and the value greater than 1 to be 1. The data standardized by original data was used in this analysis. 2 Results 2.1 Craniofacial features and ancestry identification for individuals In our samples, 11 males, seven females, and a child have intact skulls. We collected craniometrical data of these 19 skulls (Table S1). As features of children are not fully de- veloped, we excluded the data of the child skull from our Figure 2 Some of the Khotan skulls compared to the referential samples analyses hereafter. of Eastern and Western Eurasians. Sex information is marked by ♀ or ♂ Populations from different geographic regions of the under each skull. world have apparently different skull features [7,17,18], especially the shapes of orbital cavity and nasion. We ob- tional features of individual samples. served these features on our samples, and found that some samples were similar either to the Eastern Eurasians or to 2.2 Population comparison and ethnic classification the Western Eurasians, while some had characters of both sides, which suggested admixture between Eastern and It is imprecise to judge the origin of a population only by Western Eurasians (Figure 2). We calculated the allele fre- observing individual samples. Instead, many software pro- quencies of 32 features in our samples (Table S2), and grams can analyze the population data to assess the distanc- compared 12 features with ancestry identification characters es among populations. Here, we performed multiple meth- with the reference western and eastern populations. Among ods (MDS and PCA) to estimate the distances between the 12 features, seven features of most Khotan samples were Khotan and other neighboring populations and influences western types, two features were eastern types, and three fea- from the Eastern and Western Eurasians.