R haplogroup is believed to have arisen around 26,800 years ago, somewhere in Central Asia or South Asia, where its ancestor Haplogroup P is most often found at polymorphic frequencies. Cambridge University geneticist Kivisild et al. (2003) suggests that southern and western Asia might be the source of this haplogroup:
Given the geographic spread and STR diversities of sister clades R1 and R2, the latter of which is restricted to India, Pakistan, Iran, and southern central Asia, it is possible that southern and western Asia were the source for R1 and R1a differentiation.
The R haplogroup is common throughout Europe and western Asia and the Indian sub-continent, and in those whose ancestry is from within these regions. It also occurs in North and Sub-Saharan Africa. The distribution is markedly different for the two major subclades R1a and R1b.
Haplogroup R1a is typical in populations of Eastern Europe and parts of Central Europe, especially in Slavic speakers. R1a has a significant presence in Northern Europe, South and Central Asia (including Iran), Siberia, as well as India. R1a can be found in low frequencies in the Middle East, mostly in Indo-European speakers or their descendants. 
Haplogroup R1b predominates in Western Europe. R1b can be found at high frequency in Bashkortostan (Russia). R1b can be found at low frequency in Central Asia and in the Middle East, as well as North Africa. There is an isolated pocket of R1b in Sub Saharan Africa. In Europe, R1b is indicative of Celtic influence.