In a nutshell, it appears that R1b-S116 expands into three different daughter clades in three directions from somewhere in the vicinity of central France, one to Normandy and the British Isles, one to Central Europe and the Alps, and one to the Southeast (especially Iberia).
R1b-S116, in turn, could have origins in Iberia via Southern Italy, or in Central Europe, or both in parellel routes to central France. These way stations could in turn come from R1b-M269 in the Balkans or Highlands West Asia (e.g. including Iran). The answer to this question (when and where this happened) is one of the hottest questions in European archaeogenetics, because it is in furtherance of the goal of determining the archaeological culture(s) which were involved in this massive genetic transmission of the dominant Y-DNA clade today in Western Europe to its current location. To answer this question is to unveil the face of the patrilineal ancestors of most Western European men.
Maju figures that from where ever the launching point might be that the most basal R1b would have its ultimate origins in West Asia. This seems plausible enough, with R2 centered in South Asia and Western Iran, particularly in the Indus River Valley which is mostly Pakistan today, and R1 found in Iran and much of Europe and Central Asia, as well as appearing in South Asia in close correlation with hypothetical Indo-Aryan invaders (particularly R1a).
But, the fact that R1a and R1b were both present and bifurcated on the Russian steppe in the Mesolithic era, along with ancient DNA that seems to point to the Altai is the deeper place of origin for the entire Y-DNA R clade, suggests that West Asia may have received R2 from the steppe, during the Paleolithic era, rather than the other way around, with R1a and R1b arriving later in the Copper Age or early Bronze Age by different routes. It is hard to distinguish between the scenarios given the available data.
Recent ancient Y-DNA studies put examples of Y-DNA R1b and R1a on the European Steppe by the early Bronze Age or even a few centuries earlier.
In particular, European hunter-gatherer populations in Russian have ancestral Y-DNA R1 to the herders and farmers who subsequently live there, suggesting that the spread of R1 to the Russian steppe was
Corded Ware people, as expected, are predominantly R1a and have origins to the North of the Yamnaya people. The story of R1a in Europe, to quote Eurogenes, can be summed up as follows:
- Mesolithic Hunter-Gatherer from Karelia: R1a (xM198)The Corded Ware people and their successors were almost surely Indo-Europeans.
- Late Neolithic Corded Ware pastoralist from Germany: R1a (M198, M417, xZ282)
- Late Bronze Age Urnfielder from Germany: R1a (M198, M417, Z282, Z280).
The story of R1b is complicated, however, and the question of how R1b got to Western Europe remains more cryptic.
For example, Tarim Basin mummies are R1a, but the Yamnaya people, the hunter-gatherers from the area where the Yamnaya culture emerged (the Samara Valley), and the Afansievo people are R1b. This means that the Yamnaya and Afansievo people are unlikely direct ancestors for the Tarim Basin mummies, despite the fact that the Afansievo people arrived nearby before the Tarim Basin culture arose. It suggests a more Northerly route of arrival for the Tarim Basin people, or a later one, as the Indo-Iranians are predominantly R1a.
All ancient Bell Beaker Y-DNA to date are R1b, but the sample to date isn't very representative and is limited largely to Germany, while missing core areas where the Bell Beaker culture was found,
The modern distribution of R1b in Europe, however, is a decent fit to the range of the Bell Beaker culture (with declining frequencies in places where it was more marginal).
Importantly, as well, the Basque are very high in R1b, suggesting strongly that R1b was brought to Western Europe by people who were not Indo-European linguistically and that Indo-European languages only arrived in Western Europe with the Celts or realistically, with their predecessor Urnfield people whose language was probably the source of both the Italic and Celtic languages. In other words, Indo-European languages arrived in Western Europe only around the time of Bronze Age collapse. (A similar argument for an origin of Germanic languages in Northwestern Europe around the time of Bronze Age collapse is also consistent with the evidence.)
Taken to its logical conclusion, if the Yamnaya people are the forebears of the Bell Beaker and other Western European Y-DNA R1b peoples, and while the Corded Ware people are the forebears of the European R1a people, the Yamnaya people may not have been Indo-Europeans after all. Instead, they could very well have been linguistically Vasconic (i.e. linguistically in the same family as the Basque language).
As Dienekes notes, the data tend to show that "the later steppe cultures of the Sintashta and Andronovo (putative Indo-Iranians according to some), were not a continuation of the Yamnaya-Afanasievo people," as had been widely assumed before the ancient DNA data was available. Dienekes also notes genetic continuity between modern Armenians and those of the early Bronze Age.
As Maju notes, it isn't clear if R1b took a continental route, Mediterranean route, or both, to Western Europe from an origin in Southeast Europe and/or West Asia.
Maju demurs on the timing of R1b's arrival, but suggests that Atlantic Megalithic as well as Bell Beaker were likely involved, rather than a later arrival with Bell Beaker people alone.