Daic

Daic (or Tai-Kadai) is a language family that is distributed in Thailand, China, Vietnam, Laos, Burma and India. Its major branches include Kam-Sui, Tai, Hlai and Kadai. Historical records indicate that the distribution of Daic speaking populations once extended to a much larger area including most part of southeast coast of China. In particular, the possible connection between the Yue peoples, the aborigines that once dominated the southern part of China has long been suggested by ethnologists and historians.

Origin and migrations

The study of over 100 East Asian populations including 30 Daic speaking ones had reached the following conclusions. First, the Daic-speaking populations show a great deal of genetic similarity although admixture with local populations did occur after its expansion.

Secondly, a significant proportion of southern Chinese populations carry a signature of Daic-speaking populations.

Thirdly, Taiwanese aborigines are more similar to Daic-speaking populations than they are to the other Austronesian populations, that is, the Malayo-Polynesians.

Fourthly, the clustering of subfamilies of Daic-speaking populations correlates well with that based on their genetic similarity indicating limited gene flow between them after their separation.

Daic-speaking populations originated in the southern part of East Asia and then migrated northwards and eastwards with Kam-Sui probably being the oldest.

Genetic structure of Daic as revealed by Y chromosomes

Y-chromosome polymorphisms are powerful tools in delineating the genetic structure of human populations. A large number of populations in China have been studied in the last severalyears and 17 Y-chromosome single nucleotide polymorphism (SNP) haplotypes have been found in them, some of which are specific to East Asians. Major ethnic groups tend to have their own characteristicprofiles reflected by their respective Y haplotype distribution. Daic, an ethnic group dispersing from Assam to Taiwan is a diverse group and yet its genetic structure shows a distinctive profile, different from those of the other groups in East and Southeast Asia, although some resemblance between Daic and Austronesian groups, especially Taiwanese aborigines, is noticeable.

The distribution of Y-chromosome SNP haplotypes in 30 Daic populations were studied.Among the 19 SNPs studied, M119, M110, M95, and M88 are most informative in delineating the genetic structure of Daic. Linguistic and cultural classification are in general concordance with thegenetic classification although it may be transgressed due to the apparent gene flow between the major branches of Daic. For example, some populations of Kadai, a major branch of Daic, are more similar to the populations Kam-Sui, another major branch. This phenomenon may be the result of the unitary self-identification and geographic assimilation of Daic system. The geographic distribution of the three principal components (PCs) were generated by superimposingthe loading coefficients of each population on to a map, respectively.

The distribution first PC suggested a possible single origin of all the Daic populations. The second PC indicated a deep division of the Daics into two: east group and west group. The center of the east group is in Zhejiang China, and that of the west one is on the border between China and Burma. The third PC implies the migration routes southern China towards northeast, northwest and southwestduring the relocation of Daic populations. The gene flow between Daic and populations of other ethnic groups are noticeable. Han Chinese in Zhejiang and Shanghai have the highest concentration of Daic types of Y haplotypes among all the Han populations in China, suggesting a possible expansion of Daic people from southern China to Zhejiang via Kiangsi. Daic in Zhejiang and Fujian might have come by different routes, as suggested by the difference of their profiles.A diphyletic genetic structure was found in Taiwan Aborigines. The West Daic, Tai, Thai, Ahom and so on emigrated from southern China rather late. It might have happened one to two thousand years ago.