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.
Highlights
Thailand and Laos are regarded as the geographical heart of Mainland Southeast Asia (MSEA) (Fig. 1)
Archaeological evidence suggests a long history of human occupation of the area, with the oldest human remains dated to 46–63 thousand years ago from Tam Pa Ling Cave (Demeter et al 2012), and cultural remains dating to 35–40 kya (Anderson 1990; Shoocondej 2006)
Both nucleotide diversity (π) and mean number of pairwise differences (MPD) are the lowest in the TN1 group (0.0013 and 21.41, respectively), while the largest values are observed in the MO2 group (0.0026 and 42.6, respectively)
Summary
Thailand and Laos are regarded as the geographical heart of Mainland Southeast Asia (MSEA) (Fig. 1). A potential role for Thailand/Laos as a corridor between southern China and Island Southeast Asia (ISEA) is further indicated by archaeological evidence for agricultural communities that may have expanded from the center of the Yangtze valley during the Neolithic period (Higham and Higham 2009; Higham 2014). Most people speak TK languages (94.40%, in Thailand and 69.60% in Laos), while AA is the second most common language family (4.10% in Thailand and 22.70% in Laos) (Lewis et al 2016). The AA family is more diverse (27 languages in Thailand and 47 languages in Laos) than TK (16 languages in Thailand and 21 languages in Laos). The AN family is restricted to southern Thailand with just six languages (Lewis et al 2016). Both major families (AA and TK) are
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
