Southeast Asian Genetics: The Complex Roots Behind Us

Key Takeaways

• Southeast Asian (MSEA) populations are genetically very diverse, shaped by multiple ancient migration waves.
• Thai people aren't a single uniform group — research finds several genetic subgroups that differ by region and language.
• Our genomes carry traces of southern Chinese, South Asian (Indian), and indigenous ancestry.
• But ancestry results are a statistical estimate, still limited by reference databases that under-represent SEA.

Southeast Asia has one of the most complex migration histories on Earth. As a physician interested in population genetics, I want to explore why the "roots" of people here — Thais included — are more fascinating than you might think.

Why Is MSEA Genetics So Diverse?

The region has been a migration crossroads since prehistory: indigenous hunter-gatherers, early farmers from southern China, and maritime trade with India. The result is layered admixture stacked over millennia.

Thai People Have Multiple Genetic Groups

A study using hundreds of thousands of SNPs from nearly a thousand Thai individuals found that Thais can be resolved into genetically distinct subgroups by region and language family — not one homogeneous population. Some carry a high proportion of southern-Chinese ancestry; others show a clear South Asian component.

Traces of India and the Maternal Line

Recent work finds South Asian (Indian)-related ancestry across several Thai groups, consistent with ancient maritime trade, and mitochondrial DNA studies point to a maternal-line influence in those connections. These are the same tools used in ancestry DNA analysis.

What to Understand About Ancestry Results

Ancestry percentages are a statistical inference, not a fixed number, and accuracy depends on the size and diversity of the reference database — and SEA populations remain far less sampled than European ones. Results may therefore keep gaining detail as databases grow.

Author's Final Note

The more we decode this region's genetics, the clearer it becomes that being "Thai" and "Southeast Asian" is the product of many peoples meeting across thousands of years. Understanding your own roots can start with a DNA test.

References

1. Insight into the Peopling of Mainland Southeast Asia from Thai Population Genetic Structure. PubMed
2. Reconstructing the Human Genetic History of Mainland Southeast Asia: Genome-Wide Data from Thailand and Laos. Mol Biol Evol. 2021. PubMed
3. Indian Genetic Heritage in Southeast Asian Populations. PLoS Genet. 2022. PubMed
4. Unraveling the Mitochondrial Phylogenetic Landscape of Thailand. Sci Rep. 2023. Nature
5. Genetic Diversity and Ancestry of the Khmuic-Speaking Ethnic Groups in Thailand. Sci Rep. 2023. Nature
6. Insight into the Peopling of Mainland Southeast Asia (open-access full text). PMC. NCBI