This haplogroup is quite controversial today with opposing views on it's origin(s). One side sees it as Central Asia and another sees it as India. There is quite the debate in the scientific community. There are also few subclades of this group, which is a stark contrast to many in R1b.
R1a1 (now R1a1a) is supposedly the haplogroup that domesticated the horse and spread the Indo-European languages. This may be contested as new subclades and ancient DNA information is being revealed.
I myself have ancestry from Poland (a stronghold of R1a's) but my closest match on Ysearch.org at 67 markers is from India with a Genetic Distance (GD) of 14. Despite the distant timeframe for Most Recent Common Ancestor (MRCA), I contacted this person and found out that he was confused about having his closest match from Poland. Since then and we have become great friends - very very distant cousins - that both live in the US.
I originally didn't think too much about a distant connection to India, until I was in a Polish deli and as I started speaking Polish to the clerk, when a lady nearby looked at me and told the clerk that I didn't LOOK Polish. I told her that I was indeed Polish. Or was I? My genealogical research has only gotten me back to my great grand father in Poland, but I don't know much about him but his name.
My lower resolution 12 marker matches are all over Europe -England, Germany, Poland, Greece, Italy, Denmark, Norway and France and there may be what could be a remnant migration route. But what about India? The highest percentages of matches or near matches at low resolution are from Pakistan, Tajikistan and India. But low resolution may be well outside of a genealogical timeframe and maybe just hints at the past (See map image above).
I invite anyone to provide comments and especially wish to hear from other R1a1's. My journey so far into genetic genealogy takes up a good portion of my spare time as a biologist, but has made me feel more confident, outgoing and outreaching than ever before. I've enjoyed the GG presentations I've given at conferences and hope that more people will test to discover their ancient past and potential lost relatives.