I was just reading a new study in PLoS One about Y-DNA in Afghanistan, and stopped when I saw this idiotic paragraph...
R1a1a-M17 diversity declines toward the Pontic-Caspian steppe where the mid-Holocene R1a1a7-M458 sublineage is dominant . R1a1a7-M458 was absent in Afghanistan, suggesting that R1a1a-M17 does not support, as previously thought , expansions from the Pontic Steppe , bringing the Indo-European languages to Central Asia and India.
OK, first of all, the authors made a glaring error in claiming that R1a1a7-M458 dominates the Pontic-Caspian Steppe. It most certainly does not, and this information is available in the report they referenced (Underhill et al. 2010). Secondly, who cares about R1a1a STR diversity? It's not relevant, because it tells us nothing about the origins of R1a1a. In fact, there's no way anyone can accurately estimate the ages/expansion times of Y-chromosome haplogroups. Scientists have attempted such feats on many occasions in recent years, and often came up with ridiculous results. So perhaps it's now time to admit there's a problem and move on?
I'd say there's no reason why R1a1a7-M458 should be present in Central Asia and India. Simply by looking at its modern distribution and frequencies, without even attempting any complex calculations, it seems to have expanded around East Central Europe well after the early Indo-European dispersals (see here). The most sensible claim anyone can make about R1a1a7-M458 is that it's a Slavic, or even West Slavic marker, that probably originated in the people who would become Slavs in or near modern-day Poland.
The European-specific R1a1a SNP that scientists should be looking for in Central Asia, in order to track the movements of the early Indo-Europeans, is Z280. This marker has a much wider distribution in Central and Eastern Europe than M458, and perhaps that was also the case during the relevant time frames - the Chalcolithic and early Bronze Age? Indeed, it has already been found in native Central Asian samples, both in private and academic tests, and the latter results will hopefully be published soon.
To widen the net, they should also test for Z283, which is upstream to both M458 and Z280. Its present distribution hints that it might have been a common marker within the late Neolithic Corded Ware cultural horizon of the North European Plain, which is usually thought of as an early Indo-European culture. If that was the case, then in theory, based on archeological data, it might have traveled with representatives of the Eastern Corded Ware, the Abashevo culture, past the Urals and as far as East Central Asia.
Haber M, Platt DE, Ashrafian Bonab M, Youhanna SC, Soria-Hernanz DF, et al., (2012) Afghanistan's Ethnic Groups Share a Y-Chromosomal Heritage Structured by Historical Events. PLoS ONE 7(3):e34288. doi:10.1371/journal.pone.0034288
First official attempt to divide R1a1 into multiple subclades since the discovery of R-M458