Evidence page · ancient DNA
This page was going to be an animation. It is a static chart instead, and the reason is the argument: an animated migration draws a moving arrow, and an arrow asserts a continuous directed flow that a few dozen dated genomes cannot support.
Horizons and dating intervals as spans. Steppe-ancestry percentages where measured, approximate.
| Continuity | An animated line implies an unbroken population moving. The evidence is individuals, from scattered sites, radiocarbon-dated separately with error bars of a century or more |
| Direction | An arrow has a head. Ancestry proportions establish that populations mixed, not which way anyone walked. Direction is inferred from dates and distributions, and the inference is weaker than the animation would look |
| Rate | Animation speed reads as migration speed. Nothing in the data constrains rate |
| Route | A path across a map asserts a corridor. Sampling is sparse and heavily biased toward where excavation has happened |
A chart of ranges says what is known. An animation of arrows says what would be exciting.
1 · A major ancestry component associated with the Pontic-Caspian steppe spread into central and northern Europe in the third millennium BCE, and is strongly represented in Corded Ware individuals. This is well sampled and robust.
2 · A related component is present in South Asian samples, and admixture dating places the mixing broadly in the second millennium BCE. The proportion varies substantially between populations and correlates with region, language and social group.
3 · BMAC individuals carry little of it. Which is why the Dāsa-forts-are-BMAC proposal sits uneasily with the genetics, as the forts page sets out.
Admixture dating estimates when populations mixed, not when they arrived. A group that arrived and remained endogamous for several generations before intermarrying produces an admixture date that postdates its arrival.
So the second-millennium figure is a lower bound on arrival, not the arrival date — and it is habitually reported as though it were the latter. Set beside the Mitanni attestation, which requires Indo-Aryan to have differentiated and travelled west well before 1400 BCE, the case for an earlier arrival is stronger than the admixture number alone suggests.
It does not support a conquest. Ancestry proportions do not distinguish invasion from migration, from gradual infiltration, from elite dominance without population replacement. Mitanni is the documented case of the last of these: Indo-Aryan names, gods and horse vocabulary over a Hurrian-speaking population, with no demographic replacement at all.
It does not support an indigenous origin either. The component is present, it is not local in origin, and it enters within a datable window. Out-of-India requires the flow to run the other way, and the ancestry distributions across Eurasia do not fit that.
What it supports is movement, mixing, and a date range with real uncertainty in it — which is less satisfying than either story and is what the evidence says.