Origin and Dispersal
R1b is a sub-clade within the much larger Eurasian MNOPS "macro-haplogroup", which is one of the predominant groupings of all the rest of human male lines outside of Africa, and this whole group, along indeed with all of macro-haplogroup F, is believed to have originated in Asia.
Early research focused upon Europe. In 2000 Ornella Semino and colleagues argued that R1b had been in Europe before the end of Ice Age, and had spread north from an Iberian refuge after the Last Glacial Maximum. Age estimates of R1b in Europe have steadily decreased in more recent studies, at least concerning the majority of R1b, with more recent studies suggesting a Neolithic age or younger. Only Morelli et al. have recently attempted to defend a Palaeolithic origin for R1b1b2. Irrespective of STR coalescence calculations, Chikhi et al. pointed out that the timing of molecular divergences does not coincide with population splits; the TMRCA of haplogroup R1b (whether in the Palaeolithic or Neolithic) dates to its point of origin somewhere in Eurasia, and not its arrival in western Europe.
Barbara Arredi and colleagues were the first to point out that the distribution of R1b STR variance in Europe forms a cline from east to west, which is more consistent with an entry into Europe from Western Asia with the spread of farming. A 2009 paper by Chiaroni et al. added to this perspective by using R1b as an example of a wave haplogroup distribution, in this case from east to west. The proposal of a southeastern origin of R1b were supported by three detailed studies based on large datasets published in 2010. These detected that the earliest subclades of R1b are found in western Asia and the most recent in western Europe. While age estimates in these articles are all more recent than the Last Glacial Maximum, all mention the Neolithic, when farming was introduced to Europe from the Middle East as a possible candidate period. Myres et al. (August 2010), and Cruciani et al. (August 2010) both remained undecided on the exact dating of the migration or migrations responsible for this distribution, not ruling out migrations as early as the Mesolithic or as late as Hallstatt but more probably Late Neolithic. They noted that direct evidence from ancient DNA may be needed to resolve these gene flows. Lee et al. (May 2012) analysed the ancient DNA of human remains from the Late Neolithic Bell Beaker site of Kromsdorf, Germany identifying two males as belonging to the Y haplogroup R1b. Analysis of ancient Y DNA from the remains of populations derived from early Neolithic settlements such as the Mediterranean Cardium and Central and North European LBK settlements have found an absence of males belonging to haplogroup R1b.
European R1b is now known to be dominated by R-M269, and the origins of this branch are discussed further in more detail below.
Read more about this topic: Haplogroup R1b (Y-DNA)
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