In a previous experiment, I showed that ADMIXTURE at K=4 tracks the same signal of Amerindian-like admixture detected with f-statistics. I encapsulated that analysis in the globe4 calculator over at the Dodecad Project blog, and decided to use it to assess a few ancient European autosomal samples:
Please note that a very variable number of SNPs was extracted from these various samples. These results should be viewed as indicative of possible patterns that might be confirmed by a more thorough analysis. Also, please consult the globe4 post for more details on the methodology behind it, and the interpretation of the 4 components.
With these various caveats, I would say that these results seem to make some sense and to be fairly consistent with the scenario of Patterson et al. (2012):
- Oetzi and Gok4, the "farmers" seem to lack the Amerindian component
- Ajv52, and Ajv70, the northern hunter-gatherers seem to possess it
- Bra1, the Mesolithic Iberian seems to lack it as well
A broader context
The absence of the Amerindian-like admixture in South Indian Brahmins and Armenians, and its paucity Kurds and Iranians might indicate that this type of ancestry was not represented in ancient Armenians and Indo-Iranians. Indeed, all these populations possess less of this admixture than those of the North Caucasus. Cypriots possess none of it as well, where the Greek_D sample, a small 2.5% portion. In a previous analysis, I estimated a historical-era estimate of North European admixture in Greeks, and this admixture presumably incorporates the signal of Amerindian-like admixture. Additionally, an Iron Age individual from Bulgaria will soon be announced as being Sardinian-like.
The sum of these factors leads me to believe that the signal of Amerindian-like admixture did not play an important role in the formation of the Graeco-Phrygians (and their Armenian relatives) and the Indo-Iranians, or at least did so to an insignificant degree. As the former expanded westward from the PIE homeland, and the latter eastward, they would have had little opportunity to encounter this type of admixture; rather, they would have admixed with Sardinian-like individuals in the west, and Ancestral South Indian (ASI)-like or East Asian individuals in the east.
On the other hand, as Indo-European groups expanded into eastern Europe, setting off a chain of events that would eventually transform most of the northern part of the continent, and, in historical times, much of the rest of it, they would have met with Ajv-like individuals carrying the signal of Amerindian-like admixture, as well as the Oetzi/Sardinian-like farmers that had spread all the way to Scandinavia by the late Neolithic. The population formed by this mixture would have carried with it the signal of Amerindian-like ancestry, and would then transpose it across the continent. The signal would become increasingly muted westward and southward, and indeed this is what we observe.
UPDATE: It is interesting to see that South Indian Brahmins (both the Metspalu et al. sample, and my Iyer_D and Iyengar_D samples) lack this admixture, while Uttar Pradesh Brahmins do not, given the rolloff evidence for a more recent admixture of the latter. This is consistent with a historical admixture event, after the migration of Brahmin groups southwards, as described in that post.