I have perused through the data of the Dodecad Project v3 and something struck me when I saw the percentage of West European, East European, Mediterranean and West Asian admixtures among Siberian, Central Asian and South Asian peoples. Most Asian populations have more West European than East European admixture, even though R1a is far more common in North, Central and South Asia than R1b. It would make sense to deduce that most of the European admixture in Asia is East European. It doesn't seem to be the case at all. Only in some Siberian tribes is the East European component the higher than the West European (though not by much).
In addition, the West Asian component is found everywhere too, and typically exceeds both the East and West European percentages. This is to be expected in South Asia because of the proximity of West Asia, reinforced by the Demic diffusion of agriculture from West Asia towards India. A considerable amount of West Asian genes must consequently have been present in Iran, Afghanistan and Pakistan before the Indo-European invasions. This would also have included some Mediterranean admixture, which accounts for approximately 1/3 to 1/2 of of West Asian admixture in Turks, Assyrians, South Caucasians and Iranians. This explains why South Asians have more Mediterranean admixture than North-East Asians. West Asian and Mediterranean go hand in hand.
To assess the actual percentage that is pre-Indo-European, the best way is to compare the proportion of West Asian admixture found in Central and North Asians in relation to West European, East European and Mediterranean admixture. We see that Uzbeks have a considerable 25% of West Asian, but that is because they are still close to West Asia. Kyrgyzstani, on the edge of the Himalayas, only have 9.5%, the same proportion as West European. North-East Asians also have a comparable proportion of West Asian, West European and East European. Only the Mediterranean element is noticeably lower everywhere, but always present, even in northern Siberia.
The original Indo-European population that expanded from the Pontic-Caspian steppes to North and Central Asia must therefore have consisted of an admixture of people made up roughly of 30% West European, 30% East European, 30% West Asian and 10% Mediterranean. Unfortunately there doesn't seem to be any population left today with such proportion. The Balkan sample is close, but has too much Mediterranean (31%) and not enough West Asian (13%). All Caucasus populations as well as Turks have far too much West Asian (4% for Turks and over 55% for Caucasians). We could imagine that Caucasian populations got some extra West Asian admixture in the last 4000 years, for instance when Babylonians, Assyrians, Persians, then Arabs conquered the region. But cutting the percentage of West Asian doesn't solve the problem. South Caucasians (Georgians, Armenians, Turks) have too much Mediterranean in proportion to West and East European. North Caucasians (Lezgins, Agygei) have far too much West European admixture (a remarkable fact in itself considering the eastern position of the Caucasus).
In Europe itself, Germans and Poles have a reasonably well balanced proportion of all components, except the West Asian one which is too low (6% and 3% respectively). Russians are too East European (49%). However, if we assume that ancient North Caucasian people had less West Asian admixture, and we mix them with either the Poles or the Russians, the new admixture will have pretty much the right proportions of the four components. This would confirm my theory that Proto-Indo-Europeans are an admixture of R1b (West European), R1a (East European) and G2a (Caucasian) people. The lower proportion of West Asian Y-chromosomes compared to the autosomal admixture might be explained either by a genetic predisposition of haplogroup R (both R1a and R1b) to produce more sons, or by an early conquest of R1b people of Caucasian tribes, in which they men were killed or enslaved and the women taken as wives by R1b men. If R1b was originally identical to West Asian autosomes, then the percentage of West Asian autosomes would be much higher in Western Europe.
To make it easier to visualise the data I have colourised the percentages by region, using the colours of Y-DNA haplogroups used on this website that I associate most with each regional admixture, namely :
- the red of R1b for West Europeans
- the yellow of R1a for East Europeans
- the dark blue of I2a for Mediterraneans
- the grey of G2a for West Asians (could as well have been the green of J2 but I keep green for Southwest Asians)
West European / East European / Mediterranean / West Asian
Altai : 9.3 / 7.9 / 1.1 / 6.8
Dolgan : 7.1 / 8.6 / 3 / 3.2
Buryat : 1.7 / 3.5 / 1.3 / 4
Mongol : 4.9 / 4.9 / 2.8 / 5.7
Uzbek : 10.7 / 10.2 / 3.5 / 25.5
Kyrgyzstani : 9.1 / 7.2 / 2.4 / 9.5
Pathan : 12.5 / 7 / 7.8 / 25.6
Kalash : 12 / 3.8 / 0.4 / 42.9
Hazara : 8.1 /6.7 / 5.2 / 18.4
Balochi : 7.1 / 4.8 / 9.2 / 33.6
Indian_D : 9 / 5.4 / 4.1 / 12.1
AP Brahmin : 8.4 / 5 / 4.6 / 12
Tharu : 6.5 / 4.1 / 4.8 / 7.5
Vaish : 12.3 / 7.4 / 4.8 / 12.3
Lezgins : 24.3 / 3.8 / 1.1 / 64.6
Adygei : 15.7 / 6.5 / 8.3 / 62.9
Georgians : 5 / 4.1 / 17 / 72.3
Armenians : 2.1 / 0.8 / 29 / 54