Genomic continuity of Tai-Kadai-speaking populations from Southern China to Northern Thailand

Migration is a microevolutionary process that shapes cultural, societal, and genetic diversity in human populations. While previous genetic studies have examined the effects of migrations in several key areas of the world, there is a paucity of such studies in the upper Greater Mekong Subregion (GMS). The upper GMS, encompassing northern Thailand, Laos, Myanmar, and southern China, has been a major corridor for human migration and interaction between East and Southeast Asian populations for thousands of years.

We generated new genome-wide data for Tai-Kadai (TK)-speaking ethnic groups, namely Lue and Yong, from northern Thailand and integrated them with data from the upper GMS and across Asia. Our results highlight the genetic diversity among ethnic groups in the GMS, particularly the genetic continuity of TK migration from southern China to northern Thailand. The TK speakers in Thailand predominantly exhibit multiple ancestries from East Asia and Southeast Asia, with regional differentiations. The TK groups in northern Thailand primarily derive their genetic contributions from Dai-related communities, while northeastern Thai populations show a higher proportion of Lao-related ancestry. Those in central and southern Thailand display additional ancestries from other groups, such as Austroasiatic and South Asian populations. The genetic history of TK-speaking Lue populations illustrates the role of TK migration, founder effects, and historical resettlements in shaping genetic diversity.

Overall, analyses of genome-wide data reveal that the genetic background of TK speakers in Thailand is predominantly of East Asian origin, with additional contribution from Southeast Asian populations. This pattern supports the idea of sustained migration from southern China into Thailand, particularly concentrated in the northern part. Our findings reinforce the historical continuity of TK movements across the upper GMS and provide new insights into the genetic and cultural transformations that have shaped present-day Thai populations.