I will start by defining a term which will be used throughout this post; that term is "Early Western Steppe People" (EWSP). It is a shorthand, descriptive, term refering to a subset of peoples who had lived in the Pontiac Caspian Steppe (or very near) some time between the V and early III millennium BC and spoke Proto Indo-European (PIE). They can be credited with the initial expansions of the Eurasian "Steppe Belt", as described by Chernykh , eastwards from the Pontic Caspian (PC) Steppe, which involved demic movements too. They can also be credited with early westward movements roughly parallel to the Danube that carried both culture and people, the descendants of whom would eventually settle Western Europe. Note that EWSP does not necessarily designate a monolithic people or culture; that's actually the beauty of the term. The term only references those living in a certain region, at a certain time, speaking a certain language (family), and then
expanding from said region. EWSP is a funtional term and the purpose of this post is not to elaborate on the nature of the EWSP, but to examine the current distribution of certain genetic makers and elucidate their relation to ancient IE expansions.
The SNP markers R-M269 and R-M73 were dominant amongst the PIE populations of the steppes along with the earliest, major, migrations of IE people out of the PC steppe. One such migration travelled eastward to the Altai region, and beyond, while another migration went westward roughly parallel to the Danube and arrived at Hungary. Complementary to the movements of R-M269 and R-M73 out of the PC steppe, the SNP marker R-M417 moved into the PC steppe, which were mostly R-M417 deprived, after many of the EWSP had vacated the PC steppe. The most likely source the of R-M417 entering the PC steppes around the middle of the 3rd millennium BC, was the Corded Ware Culture or some closely related people around Eastern Central Europe.
Most linguists agree that the PC steppe was the seat of PIE and the source of IE language expansion around the late neolithic and early metal ages. Many of these IE expansions were accompanied by a demic spread. The evidence for a large scale demic spread being tied to the spread of IE lies in the close association of R-M417, R-M269, and R-M73 to regions that have traditionally spoken IE. There are also corresponding shifts of mtdna  and autosomal dna  which are documented to have happened around the metal ages and fit nicely with migrations originating in the PC steppe along with some if its' diluted offshoots. By the time of the common era, IE had already spread westward to Atlantic Europe and eastward to China.
A natural way of conceptualizing these early IE demic advances and their relation to modern populations (~1,500 AD), is by means of the wave model. That is to say, a model which loosely likens, ancient IE migrations spreading east and west of the PC steppes, to an expanding ripple. Adding to this analogy, regions of the Eurasian steppes which had been passed by an early IE "wave" had a good chance of experiencing additional population replacements, or later ripples, especially from people heavy in R-M417. There are, however, unique regions along the path of these waves which were far more likely to retain the genetic markers of these EWSP. These areas will be explored in detail over the course of this post. The wave model is an appropriate match for the spread of IE given the ease of travel in the Eurasian steppes along with the higher probabilities of population replacement. According to the wave model, we should expect to find the earliest remnants of
the IE migrations at opposite ends of the IE world. As an appeal to intuition, one can imagine a rock falling into a pond whereby the ripples that formed earliest will have travelled the furthest distance from the origin in a given time period.
Upon inspection of the western edge of the traditional IE world, Western Europe, and the eastern edge, China and the Altai region, we do indeed find a unique genetic link between the two distant regions. That genetic link is the concentrated levels of R-M269 and R-M73. The near absence of R-M269 and R-M73 in between Western Europe and Central Asia  fits with the idea that the Western Eurasian steppes were unstable enough to have experienced population replacement since the time of the earliest IE migrations. In fact, if the polarized distributions of R-M269 and R-M73 were the only problem we cared to solve, the steppes would still be good candidate for the starting point of where the two haplotypes started to (rapidly) move away from each other. If that starting point was instead the Middle East or Medieval Europe, whereby some combination of R-M269 and R-M73 people moved away from each other to eventually settle opposite poles of the IE world we
would still have to explain the lack of R1b along the trail of their divergent migrations, and on top of that we would have to deal with the population continuity that existed in the Middle East or Medieval Europe.
Evidence that early IE migrations from the PC steppes were heavy in r1b comes from the striking correlation between R-M269 and R-M73, and the regions which had been settled by the earliest IE migrants. Some of the most well established early IE settlements outside the Black Sea region include the southern Urals and the Altai region . Both regions are "hotspots", local peaks, for the frequency of r1b   . The story of r1b's expansion with EWSP is then cooberated in some manner by ancient ydna, mtdna, the linguistic structure within IE, and the archeological evidence for migration.
Not only do we find r1b concentrated at the western and eastern poles of the IE world, we selectively find r1b concentrated at the edges of the IE world where deeper continuity can be expected! The kind of continuity required to retain the uniparental markers of EWSP exists for the populations at the eastern and western edge of the traditional IE world for which r1b has a local frequency peak. Starting with the eastern end of the IE world we have greater concentrations of R-M269 and R-M73 in the southern Urals, among the Bakshirs, the Altai region, and, although minimal in an absolute sense, we still find a concentration of the two haplotypes in China along the steppe-agriculture border region.
The r1b hot spot in the southern Urals is represented by the Bashkirs  . The Bashkirs reside in an area that once formed the eastern extension of yamnaya culture and the location of communities that had formed an important economic link in Chernykh's "Steppe Belt" . East of the Urals, in the Altai mountains and the surrounding area, we observe another dramatic increase in the frequency of R-M269 plus R-M73 . This particular region corresponds to the location of the Afanasevo Culture which is believed to be one of the earliest offshoots of IE east of the Urals and is thought to have played a central role in the eastward expansion of the "Steppe Belt" . The ancient inhabitants of the Afanasevo Culture may have even spoken a Tocharian language. It is clear that the r1b pair has local peaks in some of the most important centers of the earliest IE expansions but the question remains as to who actually brought r1b to the aforementioned regions.
To shed some light on the timing of r1b's appearance in the southern Urals and the Altai region we can consider the relative amount of genetic continuity in the populations of those regions. There is actually a smaller genetic distance between the ancient Mesolithic Uznyi Oleni Ostrov/Popova along with the Bronze Age Bolshoy Oleni Ostrov and the modern Bashkirs along with the modern populations near the Altai Mountains as compared to the distance with other modern populations . In other words the Bashkirs of the southern Urals and the natives around the Altai Mountains share greater continuity with the Uznyi Oleni Ostrov/Popova and Bolshoy Oleni Ostrov like populations of ancient East Europe/Central Asia. Thus, r1b is simultaneously associated with the locations of the earliest centers for IE expansion and populations with the closest genetic ties to the older West Eurasian lineages of Eastern Europe and Central Asia. This indicates an earlier
presence of r1b in the southern Urals and the Altai area, consistent with an introduction by earliest IE expansions. Perhaps we should not be surprised that both the southern Urals and the Altai region display a higher degree of genetic continuity. According to a study on Southeast Asian populations, rates of endogamy are generally greater in the highlands . If this result can be generalized to Eurasia then we should have expected greater genetic continuity in mountainous regions such as the Urals and the Altai. Incidentally, the theory that populations of the highlands typically exhibit greater genetic continuity might help us to understand the reason for the higher frequencies of G2a in the mountainous regions of Europe.
Further east, along Chernykh's ancient "Steppe Belt", is Central and Northeastern China. Here, the absolute frequency of r1b is very small, which is what we would expect given the overall paucity of West Eurasian lineages in Central and Northeast China. However, it is worthwhile to note the increased frequency of R-M269 plus R-M73 along the steppe-agricultural border in China, as compared to the frequencies of the r1b pair in other parts of China along with the increased ratio of R-M269 plus R-M73 to R-M17 near the steppe-agricultural border . This small but observable concentration of r1b in the steppe-agricultural border lands of China reinforces the idea of a steppic introduction of the r1b pair to China. By contrast, R-M17 has a rather diffuse presence in China that would make it hard to distinguish demic diffusion via Chernykh's "Steppe Belt" versus demic diffusion by the Silk Road, for example. In the case of China, the earlier steppe
migrations, which had pushed the the "Steppe Belt" into China, would be better preserved from the latter steppe migrations, along the steppe-agricultural border. The reason for this is that shortly after the "Steppe Belt" had pushed into China, the agricultural based civilizations at the steppe border developed policies that discouraged further introgression of steppe peoples . Since R-M269 plus R-M73 concentrates at the Chinese steppe-agricultural border, while R-M17 does not, we have yet another indication that the r1b pair came alongside the eastward expansion of Chernykh's "Steppe Belt".
At the western end of the traditional IE world sits Western Europe. Western Europe is extremely rich in m269 . The demic and linguistic relation between modern Western Europeans and EWSP is largely defined by the following events. Around 3000–2800 BC, a migration originating in the PC steppes moved westward, roughly parallel to the Danube, and carried a branch of IE which would uniquely lead to the survived languages of Italic, Celtic, and perhaps Germanic . Isotopic evidence, cooberated with archeological, cultural, knowledge, indicates that a significant percentage of the people found in the kurgan graves of eastern Hungary had non-local origins, and most likely came from Romania or the PC steppes circa 2,900 BC . The descendants of these EWSP that had settled the Carpathian Basin would in turn spread to much of Western Europe as a significant component of the Eastern Bell Beaker expansion around the middle of the third millennium BC .
Around the same time we see a large growth in the population of Germany , surely connected to the expansion of the Eastern Bell Beakers. It is important to note that the earliest finding of m269 in the western half of Europe comes from a Bell Beaker site in Germany around the same time period as the development and expansion of the Eastern Bell Beakers. Notice that the conclusion from Hyde  is consistent with the results from Desideri  which supports an expansion of Eastern Bell Beakers around the middle of the 3rd millennium BC, which included male lineages separate from the Western Bell Beakers. The models from Hyde and Desideri are also consistent with the paper from Grube  which puts forth evidence that a significant percentage of Bavarian Bell Beaker people had non-local origins, primarily pointing to an origin in the Northeast direction. The characterization of the Bavarian Bell Beakers as being a mobile people applies to men as
well, whereby 21% of the subjects determined to be male were considered as "mobile". The Eastern Bell Beaker expansion would come to dominate Western Europe in terms of linguistics. Based on the linguistic domination, demic spread and the resulting population distribution, the corresponding population growth, and the presence of R-M269 in the Eastern Bell Beakers  it is safe to suppose that Eastern Bell Beakers are responsible for much of the R-M269 in modern (circa 1,500 AD) Western Europe. Also, based on the linguistic and genetic heritage that Eastern Bell Beakers have with EWSP, along with the bronze age novelty of R-M269 in Germany, the R-M269 carried by the Eastern Bell Beakers is mostly derived from the EWSP. By connecting the dots we can say that most West European R-M269 is derived from the EWSP.
Consistent with the idea of an EWSP, dominated by R-M269 plus R-M73, migrating to Western Europe is the observation that the U2e found in the ancient Scythians of the PC steppe shares more matches with modern Western Europeans than it does with modern Eastern Europeans . Mtdna U2e in Europe is a likely marker of EWSP given long term presence of U2e in the Western Russia and the apparent metal age introduction of U2e in Western and Central Europe. From the same study we can see that ancient Scythian mtdna U5a, shares more matches with modern West Asians than modern Eastern Europeans . At the same time ancient Scythian mtdna haplogroups H2a1, I3, and T2 have more matches with modern Eastern Europeans than they do with modern Western Europeans or modern West Asians . Considering the uniparental genetic markers of modern West Eurasians and ancient Scythians from the PC steppes, we can conclude that R-M269 plus R-M73 is more closely associated with
the older, West Eurasian, mtdna lineages of the PC steppes (U2e and U5a) while R-M417 is more closely associated with the latter, West Eurasian, mtdna lineages of the PC steppes (H2a1, I3, and T2). This observation falls in line with the hypotheses that EWSP were dominated by the r1b pair while latter peoples of the PC steppes were dominated by R-M417.
Thus, a very clear pattern emerges; R-M269 plus R-M73 peaks locally, with significant frequencies, in the very regions where the more important settlements of the earliest IE migrations from the PC steppes were located. This includes the southern Urals (former mining settlements for early IE settlers), the Altai region (formerly the Afanasevo Culture), West Asia (formerly host to the speakers of the Anatolian languages), and the slightly controversial example of Western Europe (formerly home to the migratory Eastern Bell Beakers). What's more is that these same regions share stronger mtdna links to the more ancient populations of the PC steppes, and nearby, as revealed by ancient DNA. In the Urals and the land east of the Urals, mtdna relatedness to the ancient Uznyi Oleni Ostrov/Popova and Bolshoy Oleni Ostrov like populations, peaks in both the southern Urals and the general Altai region. In West Eurasia, the U2e of the ancient Scythians, and thus the
ancient PC steppes, shares the most matches with modern Western Europeans. Also in West Eurasia, the U5a of ancient Scythians, and thus the ancient PC steppes, shares the most matches with modern West Asians. Another emergent pattern, pointed out by David Anthony, are the three migrations from the PC steppes which can be derived independently from archeology and linguistics which appears to be some of the earliest, significant, IE migrations out of the PC steppe . This pattern provides strong support for the hypothesis that the EWSP were dominated by R-M269 plus R-M73, since each of the three migrations moved in the direction of a major settlement of the r1b pair and most major settlements of the r1b pair (Western Europe, West Asia, and the Altai region) were host to the three earliest branchings of Proto Indo-European (Anatolian, Tocharian, and Italo-Celtic). Thus, the archeological, linguistic, modern DNA, and ancient DNA all cooberate the claim
that the earliest IE migrations out of the PC steppes were dominated by R-M269 plus R-M73.
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Esther J. Lee 1 , Cheryl Makarewicz 2 , Rebecca Renneberg 1 , ... 2012