It looks like there is a need to remind about some basic facts.
1. Genetic studies used for describing population history are complementary to such sciences like History and archeology.
2. According to archeological evidence undeniably there was migration from Yamna culture to Central Asia, which formed Afanasevo culture(3000 - 1700 BC). Before that there is no sign of migration through Ural Mountains, and cultures on both sides of them are distinct in that period in western steppes there were herders while in Central Asia there ware horse hunters.
3. Anthropologically people from Afanasevo, Andronovo and BMAC ware similar to those from Europe.
4. Genetic study shows that R1a-M417 is about 5800 years old(coalescent time), that means it originated about 3800 BC which correspond to Yamna expansion 3400-2700BC. Other lineages of R1a are very rare, probably because R1a was rare haplogroup, but one family made success to go to the vast grass lands taking their wagons polled by horses, so they didn't need to have a camp on side of a river.
5. Ancient DNA reveals migration from Europe to Asia but not in opposite direction.
6. Goga has posted study which concludes that diversity of SNP's is higher in India then elsewhere. But in India there is lack of old subclades it is evident that there was migration from areas with older lineages.
Every single evidence shows that Indo-European movement was from Pontic Steppe to Central Asia but not in opposite direction.
In that case is totally irrelevant where R1a originated, because it is old Paleolithic haplogroup. It could have originated every ware from Atlantic coast to Altai Mountains 25 000 years ago.