Indo-Aryan Admixture: What qpAdm, f-Statistics, IBD, and Y-DNA Can Actually Resolve

The Answer We Can Defend

The strongest current model is deliberately broader than the cultural labels used in the original 2024 article. A Steppe-related population interacted with southern Central Asian farmer-related populations during the first half of the second millennium BCE, probably around the Turan periphery. Descendants of that already-mixed population then contributed ancestry to northern South Asia, where it combined with an AASI-rich substrate.

This is a route class, not a recovered itinerary. Sintashta, Alakul, Srubnaya, Czech Corded Ware, Sappali, Shahr-i-Sokhta, and Uzbekistan Bronze Age groups are sampled proxies. A proxy can fit because it occupies the right ancestry geometry without being the literal historical population.

What the Genetic Evidence Shows

The refreshed analysis uses the AADR v66.0 reference panel and a deterministic battery of qpAdm, f3, f4, chronology, ancient-IBD, and Y-chromosome checks. The semantic baseline remained stable after re-verification: 72 qpAdm fits, 22 focused f4 contrasts, 1,516 ancient-IBD pairs, and 6 confirmed personal Y markers.

The older article’s approximately 35% Steppe estimate remains useful as a description of particular fitted proxy models. It should not be read as proof that ancestry stayed historically constant from Corded Ware through Andronovo, or that those archaeological cultures were successive ancestors of the target.

Which Steppe Culture?

No exact Steppe culture is identified. Samara Srubnaya is the highest chronology-weighted operational proxy in the finite refinement screen, but Czech Corded Ware passes more panels. Removing the chronology component ties their leading configurations. That is a warning against translating “best score” into “the ancestors were Srubnaya.”

Which Farmer Culture?

The broad Central Asian farmer-related requirement is supported, but Sappali, Shahr-i-Sokhta BA1, and cleaned Uzbekistan Bronze Age cohorts remain competing proxies. In 24 focused farmer f4 contrasts, none crossed the project’s resolution threshold. The original statement “no direct BMAC contribution” therefore exceeded the test: the tested Gonur configurations failed, but that does not eliminate every BMAC-related or unsampled Turan population.

“Farmer-related” is an ancestry label, not proof that the contributing individuals belonged to one archaeological culture or practiced a particular subsistence economy. The historically relevant population may be absent from the ancient-DNA record.

When Did Contact Occur?

The best-supported synthesis is a broad 1900–1500 BCE interval. A local DATES run centers near 1743 BCE, but its 68% interval spans approximately 2608–878 BCE. The point estimate is not precise enough to name a single event.

What Ancient IBD Adds

The ancient network was built backward from public ancient individuals using imported ancIBD result tables. At an 8 cM threshold, Steppe–Swat pairs show 143 observed edges against 73.7 under a degree-preserving graph null—an approximate 1.94× excess.

The DA9 consumer match that initiated the search is approximately 5.4 cM, below the ancient-network 8 cM floor, and is not a CasperHub/ancIBD edge. DA9 is female, so it cannot support a paternal-line claim. “Alakul–Maitan” is shorthand for an IBD-generated, multi-label candidate set—not one archaeological population or a reverse genealogy into this genome.

What Y-DNA Adds

Big-Y evidence securely places the personal paternal line at R-L657 > R-FTF40903. Bronze Age Steppe samples provide an R-Z94 sibling-branch transect compatible with the broader chronology. Y-DNA does not estimate autosomal mixture proportions, and the current ancient audit contains no exact R-L657 or R-FTF40903 carrier.

Method and Claim Limits

qpAdm asks whether a proposed target-as-mixture model is rejected relative to specified reference populations. A high p-value does not prove the sources are true, and the highest p-value is not automatically the best historical model. The search therefore freezes candidate sets, rotates sources and references, applies coefficient and chronology gates, checks source-order symmetry, and reports the surviving model class rather than a single winner.

The deterministic Lean checks used by the research pipeline verify declared implications and reporting honesty. They do not prove ancestry or historical reality. The publishable claim ceiling is: Compatibility among tested proxies, not unique population identity, direct descent, or a literal migration chain.

Conclusion

The older “35% Steppe, no BMAC, Andronovo vector” headline was too sharp. The updated evidence supports a strong Steppe-related signal, a real southern Central Asian farmer-related signal, and a broad 1900–1500 BCE contact window. It does not yet tell us whether the decisive historical community called itself Sintashta, Alakul, Srubnaya, BMAC, or anything preserved in modern archaeological labels.

That uncertainty is not a failure of the analysis. It is the result: this consumer-array target robustly separates broad ancestry axes while resolving cultures within those axes only weakly.

Primary references

• Allen Ancient DNA Resource, version 66.0.
• Narasimhan et al. 2019, South and Central Asian population formation.
• Ringbauer et al. 2024, ancient IBD and mobility.
• Harney et al. 2021, qpAdm performance and best practices.
• Yüncü et al. 2024, qpAdm under recent and complex demographies.