Genetic studies of present-day people in South Asia and nearby regions support a single major expansion of modern humans into Asia, followed by long local histories. These deep roots are important because later ancient-DNA work uses them to model early South Asian ancestry that is not closely related to West Eurasian (West Asian/European) groups.
Archaeology at Fa-Hien Lena in Sri Lanka documents Late Pleistocene human activity and specialized hunting in tropical rainforest settings. While this is not ancient DNA, it helps anchor the Upper Paleolithic time depth in South Asia that later genetic models aim to explain.
Ancient DNA from northern South Asia (including the Swat Valley region) showed that Steppe pastoralist-related ancestry becomes detectable in later individuals compared with earlier local profiles. This provided a time-structured genetic signal for post-urban Indus-era population changes in the northwest of the subcontinent.
Iron Age archaeological horizons (such as the Painted Grey Ware culture) provide the broader historical context for the period when multiple ancestry streams had already mixed in parts of South Asia. Ancient-DNA timelines are often compared to these archaeological sequences to understand how genetic change relates to shifts in settlement, technology, and social organization.
Genome-wide studies proposed that many South Asian groups can be described as mixtures of two broad ancestry components: Ancestral North Indians (ANI), related to West Eurasians, and Ancestral South Indians (ASI), more distinctive to the subcontinent. This model became a baseline for later ancient-DNA studies that sought to identify real prehistoric source populations behind these statistical components.
Using patterns in present-day genomes, researchers estimated that much ANI–ASI mixture occurred roughly 1,900–4,200 years before present. They also argued that India shifted from frequent inter-group mixing to much more endogamy (marriage within groups), which affects how later genetic patterns formed and persisted.
A genome from a burial at the Indus Valley Civilization site of Rakhigarhi provided the first widely discussed direct ancient-DNA evidence from an IVC context. The study reported ancestry related to ancient Iranian-lineage hunter-gatherers (before farming) and to South/East Eurasian hunter-gatherer lineages, and it reported no Steppe pastoralist ancestry in this individual.
A major ancient-DNA synthesis analyzed hundreds of ancient individuals across Central and South Asia to model South Asian population formation. It argued that a key ancestry gradient involved Iranian-related hunter-gatherer ancestry and ancestry related to deeply South/East Eurasian lineages (often modeled with proxies such as Andaman Islanders), and that Indus-Periphery-related groups were central to later South Asian ancestry formation.
Researchers introduced and popularized the term AASI (Ancient Ancestral South Indian) to refer to a major deep ancestry component in South Asia that is not closely related to West Eurasian groups. Because few (or no) confirmed AASI ancient genomes are available, studies often infer AASI using statistical modeling and imperfect present-day proxies, which is a key limitation of the field.
The large ancient-DNA study tested whether Bronze and Copper Age populations from Turan (including BMAC-related groups) could be major sources for the Iranian-related ancestry in South Asia. It rejected these as plausible major direct sources based on ancestry ratios, reshaping how researchers model gene flow between Central Asia and South Asia in the Bronze Age.
By combining Indus-Periphery-like ancestry, AASI-related ancestry, and Steppe pastoralist-related ancestry, researchers proposed a coherent model for how many present-day South Asian populations formed after the Indus Valley Civilization period. In this model, different regions and groups formed through varying mixtures of these sources, helping explain north–south genetic gradients seen today.
New radiocarbon dates from human tooth enamel at Mehrgarh suggest farming life in the Indus region began later than some earlier chronologies proposed. This matters for genetic interpretations because the timing of farming influences when and how gene flow between South Asia and neighboring regions could have occurred.
Ancient DNA evidence for South Asian population formation (Upper Paleolithic–Iron Age)