Autosomal STRs Provide Genetic Evidence for the Hypothesis That Tai People Originate from Southern China

et al. (2013) Autosomal STRs Provide Genetic Evidence for the Hypothesis That Tai People Originate from Southern China. PLoS ONE 8(4): e60822. doi:10.1371/journal.pone.0060822 Autosomal STRs Provide Genetic Evidence for the Hypothesis That Tai People Originate from Southern China Zhaoqing Yang 0 Hao Sun 0 Chi Zhou 0 Xiaoqin Huang 0 Keqin Lin 0 Lei Shi 0 Liang Yu 0 Shuyuan Liu 0 Jiayou Chu 0 David Caramelli, University of Florence, Italy 0 The Department of Medical Genetics, Institute of Medical Biology, Chinese Academy of Medical Sciences & Peking Union Medical College , Yunnan , China Tai people are widely distributed in Thailand, Laos and southwestern China and are a large population of Southeast Asia. Although most anthropologists and historians agree that modern Tai people are from southwestern China and northern Thailand, the place from which they historically migrated remains controversial. Three popular hypotheses have been proposed: northern origin hypothesis, southern origin hypothesis or an indigenous origin. We compared the genetic relationships between the Tai in China and their ''siblings'' to test different hypotheses by analyzing 10 autosomal microsatellites. The genetic data of 916 samples from 19 populations were analyzed in this survey. The autosomal STR data from 15 of the 19 populations came from our previous study (Lin et al., 2010). 194 samples from four additional populations were genotyped in this study: Han (Yunnan), Dai (Dehong), Dai (Yuxi) and Mongolian. The results of genetic distance comparisons, genetic structure analyses and admixture analyses all indicate that populations from northern origin hypothesis have large genetic distances and are clearly differentiated from the Tai. The simulation-based ABC analysis also indicates this. The posterior probability of the northern origin hypothesis is just 0.04 [95%CI: (0.01-0.06)]. Conversely, genetic relationships were very close between the Tai and populations from southern origin or an indigenous origin hypothesis. Simulation-based ABC analyses were also used to distinguish the southern origin hypothesis from the indigenous origin hypothesis. The results indicate that the posterior probability of the southern origin hypothesis [0.640, 95%CI: (0.524-0.757)] is greater than that of the indigenous origin hypothesis [0.324, 95%CI: (0.211-0.438)]. Therefore, we propose that the genetic evidence does not support the hypothesis of northern origin. Our genetic data indicate that the southern origin hypothesis has higher probability than the other two hypotheses statistically, suggesting that the Tai people most likely originated from southern China. - Tai people are a subgroup of Tai language speakers who are widely distributed in Southeast Asia and the Yunnan Province of Southwest China. Tai people are the largest ethnic group in Thailand, but this ethnic group is called different names in other countries. They are called Dai in China, Shan in Burma and Lao in Laos. Although different names are used in different countries or in different literature, most researchers agree that these Tai speakers share a recent common origin [1,2,3,4,5,6]. For clarity, in this paper, we use Tai to represent the Tai speakers of Southeast Asia and Southwest China. Even though most researchers agree that Tai people share a recent common origin, the source of the Tai migration remains controversial. There are several popular hypotheses for the place from which the Tai people came, and these hypotheses can generally be summarized into two types: an indigenous origin hypothesis [3,7,8,9] and a migration hypothesis [1,2,5,6,10,11,12,13]. The migration hypothesis can be further divided into migration from northern China (northern origin hypothesis) [1,2,10,11] and migration from southern China (southern origin hypothesis) [5,6,12,13]. The theory that the Tai originated from northern China was introduced in the late 19th and early 20th centuries [1,2,10,11,14]. The most important proponent was W. C. Dodd, and his theory was widely accepted by scholars of Thailand and Burma. He believed that Tai people originated from the temperate grasslands in northern China, where they lived until Chinese Han people drove them south approximately 3,000 years ago. According to this theory, Tai people were first driven to central China from the north by the Han, and then they gradually moved to parts of southwestern China, such as Yunnan and other countries in Southeast Asia, after the 6th century B. C. Dodd also suggested that Tai people and Mongolians share a recent common origin [1]. The southern origin hypothesis was proposed in the early 20th century by Davies [12] and has been systematically expounded by Chinese scholars, such as Fan [13] and Huang [6]. These researchers believe that Tai people came from southern China and that their ancestors are the Yue people who were indigenous people in the south of ancient China. According to their theory, Tai people and the other Tai-Kadai-speaking ethnic groups in southern China, such as the Zhuang and the Mulao, have a recent common ancestor. Consistent with this hypothesis, todays Chinese Dai and other Tai-speaking people in other countries migrated from southern China approximately 1,000 or 2,000 years ago. In 1900, the British scholar Scott suggested that Tai people were indigenous people of southwestern China and have evolved into an independent ethnic group [7]. Some Chinese scholars have attempted to prove the theory of indigenous origin using historical records [15] and archaeological evidence [9]. These scholars proposed that Tai people should be indigenous people of southwestern China, such as the Austro-Asiatic speakers (the Wa and the Bulang in China). The supporters of the indigenous theory believe that Tai people originated from the Yunnan Province of China and north of Indochina. In addition to archeological, linguistic and historical investigations, genetic methods are also very useful for inferring some demographic events, such as population migrations, admixture and the relationships of different populations. The various theories of the origin of the Tai people were mostly derived from historical, cultural and archeological evidence but lack biological support. In this study, we use genetic methods to explore which hypothesis about the origin of the Tai is most likely correct. Nineteen ethnic groups were analyzed. Three Dai populations (Dai_Dehong, Dai_Yuxi and Dai_Xishuangbanna in Figure 1), which come from the main branches of Tai people in China, were used to represent the genetic structure of the Tai. To test the hypothesis that the Tai came from northern China, a Mongolian population was chosen. Some northern Altaic speakers (Sala and Dongxiang), who have close relationships with Mongolian people, were also chosen. We refer to the Mongolian, Sala and Dongxiang as the northern origin of the Tai. In the southern origin hypothesis, many Chinese ethnologists [5,6,13] (...truncated)