New insights from Thailand into the maternal genetic history of Mainland Southeast Asia

Wibhu Kutanan,Mark Stoneking,Alexander Hübner,Enrico Macholdt,Andrea Brunelli,Sukhum Ruangchai,Silvia Ghirotto,Daoroong Kangwanpong,Jatupol Kampuansai,Metawee Srikummool,Leonardo Arias,Roland Schröder,Pittayawat Pittayaporn

doi:10.1038/s41431-018-0113-7

Abstract

Tai-Kadai (TK) is one of the major language families in Mainland Southeast Asia (MSEA), with a concentration in the area of Thailand and Laos. Our previous study of 1234 mtDNA genome sequences supported a demic diffusion scenario in the spread of TK languages from southern China to Laos as well as northern and northeastern Thailand. Here we add an additional 560 mtDNA genomes from 22 groups, with a focus on the TK-speaking central Thai people and the Sino-Tibetan speaking Karen. We find extensive diversity, including 62 haplogroups not reported previously from this region. Demic diffusion is still a preferable scenario for central Thais, emphasizing the expansion of TK people through MSEA, although there is also some support for gene flow between central Thai and native Austroasiatic speaking Mon and Khmer. We also tested competing models concerning the genetic relationships of groups from the major MSEA languages, and found support for an ancestral relationship of TK and Austronesian-speaking groups.

Highlights

The geography of Thailand encompasses both upland and lowland areas, and Thailand is one of the most ethnolinguistically-diverse countries in Mainland Southeast Asia (MSEA)
Samples were analyzed from 560 individuals belonging to 22 populations classified into four groups: (1) the central Thais (CT); (2) the Mon; (3) the TK speaking groups from northern Thailand, including Yuan, Lue and Khuen (TKH); and (4) the ST speaking Karen (Table 1 and Fig. 1)
High genetic diversities were observed in CT populations (h = 1.00 ± 0.01 in CT2; haplogroup diversity = 0.99 ± 0.01 in CT2 and CT4; S = 346 in CT2) and Mon from central Thailand (MO7) (MPD = 39.32 ± 17.70 and π = 0.0024 ± 0.00119) (Table 1)

Summary

Introduction

The geography of Thailand encompasses both upland and lowland areas, and Thailand is one of the most ethnolinguistically-diverse countries in Mainland Southeast Asia (MSEA). The majority of the people (29.72%) are called Thai or Siamese and speak a central Thai (CT) language that belongs to the TK family. Since it is the country’s official language, the number of people speaking the CT language as their primary or secondary language is ~40 million [1], or ~68% of the population. Linguistic and archaeological evidence suggests that the prehistorical TK homeland was situated in the area of southeastern or southern China, and that they spread southward to MSEA around 1–2 kya [5, 6] This process could have occurred via demic diffusion

Methods

Results

Conclusion