Complete mitochondrial genomes of Thai and Lao populations indicate an ancient origin of Austroasiatic groups and demic diffusion in the spread of Tai–Kadai languages

Abstract

The Tai–Kadai (TK) language family is thought to have originated in southern China and spread to Thailand and Laos, but it is not clear if TK languages spread by demic diffusion (i.e., a migration of people from southern China) or by cultural diffusion, with native Austroasiatic (AA) speakers switching to TK languages. To address this and other questions, we obtained 1234 complete mtDNA genome sequences from 51 TK and AA groups from Thailand and Laos. We find high genetic heterogeneity across the region, with 212 different haplogroups, and significant genetic differentiation among different samples from the same ethnolinguistic group. TK groups are more genetically homogeneous than AA groups, with the latter exhibiting more ancient/basal mtDNA lineages, and showing more drift effects. Modeling of demic diffusion, cultural diffusion, and admixture scenarios consistently supports the spread of TK languages by demic diffusion.Electronic supplementary materialThe online version of this article (doi:10.1007/s00439-016-1742-y) contains supplementary material, which is available to authorized users.

The paternal and maternal genetic history of Vietnamese populations

“…MtDNA variation in Thailand supports a model of demic diffusion of TK speakers (12), while recent studies based on ancient DNA provide further evidence for Neolithic and Bronze age migrations from East Asia (13), and explain present-day SEA populations as the result of admixture of early mainland Hòabìnhian hunter-gatherers and several migrant groups from East Asia associated with speakers of the AN, AA and TK languages (14). ST languages are predicted to have diverged 5.9 kya in Northern China, and reached Vietnam around 0.5-0.15 kya (15).…”

Contrasting maternal and paternal genetic variation of hunter-gatherer groups in Thailand

“…With 5 haplotypes defined, the Maniq showed higher diversity values (h = 0.82 ± 0.08; MPD = 29.85 ± 14.16; π = 0.0018 ± 0.00097; S = 64) than the Mlabri. However, both of them have lower genetic diversity values than other populations from Thailand ( Figure S1) [31][32] .…”

“…By contrast, there are three basal haplogroups (M17a, M21a and R21) observed in the Maniq. When combined with sequences from other populations 11,[31][32] (Table S1) Figure S3).…”

Y chromosomal evidence on the origin of northern Thai people

“…We first constructed two competing models (Fig 1), which are admixture and tree-like models based on our previous results [21,22]. …”

“…On the other hand, a coalescent modelling using mtDNA genome data indicated southern China as the most probable origin of the KM, without admixture with LW groups in northern Thailand [22]. Y chromosomal data of KM and of their linguistic and geographic neighbours in northern Thailand have been reported, but they have been limited to STR markers [10,23].…”