Abstract
BackgroundThe demographic history of South and Southeast Asia (S&SEA) is complex and contentious, with multiple waves of human migration. Some of the earliest footfalls were of the ancestors of modern Austroasiatic (AA) language speakers. Understanding the history of the AA language family, comprising of over 150 languages and their speakers distributed across broad geographical region in isolated small populations of various sizes, can help shed light on the peopling of S&SEA. Here we investigated the genetic relatedness of two AA groups, their relationship with other ethno-linguistically distinct populations, and the relationship of these groups with ancient genomes of individuals living in S&SEA at different time periods, to infer about the demographic history of this region.ResultsWe analyzed 1451 extant genomes, 189 AAs from India and Malaysia, and 43 ancient genomes from S&SEA. Population structure analysis reveals neither language nor geography appropriately correlates with genetic diversity. The inconsistency between “language and genetics” or “geography and genetics” can largely be attributed to ancient admixture with East Asian populations. We estimated a pre-Neolithic origin of AA language speakers, with shared ancestry between Indian and Malaysian populations until about 470 generations ago, contesting the existing model of Neolithic expansion of the AA culture. We observed a spatio-temporal transition in the genetic ancestry of SEA with genetic contribution from East Asia significantly increasing in the post-Neolithic period.ConclusionOur study shows that contrary to assumptions in many previous studies and despite having linguistic commonality, Indian AAs have a distinct genomic structure compared to Malaysian AAs. This linguistic-genetic discordance is reflective of the complex history of population migration and admixture shaping the genomic landscape of S&SEA. We postulate that pre-Neolithic ancestors of today’s AAs were widespread in S&SEA, and the fragmentation and dissipation of the population have largely been a resultant of multiple migrations of East Asian farmers during the Neolithic period. It also highlights the resilience of AAs in continuing to speak their language in spite of checkered population distribution and possible dominance from other linguistic groups.
Highlights
The demographic history of South and Southeast Asia (S&SEA) is complex and contentious, with multiple waves of human migration
We performed a principal components analysis (PCA), as implemented in EIGENSOFT [31], on 939 individuals’ genomes, 92 of which belonged to AAs of India (AAI), 97 to AAs of Malaysia (AAM), and 750 individuals from the neighboring Indian, Malaysian, and other Eurasian populations
On the other extreme of the PC1-axis are individuals belonging to AAM, Austronesians (ANS), some Tibeto-Burman speaking (ATB) subgroups, and most East Asian (EA) groups
Summary
The demographic history of South and Southeast Asia (S&SEA) is complex and contentious, with multiple waves of human migration. Occupying about 5% of the total landmass, S&SEA is home to over 26% of the world population [1] of diverse ethnolinguistic groups This region has witnessed multiple waves of anatomically modern human (AMH) migration [2, 3]; the earliest footfalls, as estimated from uniparental genetic data, are as ancient as the first wave of AMH migration out of Africa, ~ 60,000 years ago (60 KYA) [4,5,6]. AAs are geographically widespread and their language is spoken throughout mainland Southeast Asia (MSEA), central, northeastern and eastern parts of the Indian peninsula as well as the Nicobar Islands [13]. To date, almost all AAs across S&SEA, such as Malaysian Negritos, Mlabri of Thailand, Nicobarese from the Nicobar Islands, and Munda speakers from India remain predominantly hunter-gatherers or partial and primitive agriculturists who hardly depend on agriculture for sustenance [10, 19, 20, 27, 28]
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