BTW, I mentioned earlier that the fact that the Germanic lands, Croatia, and Tanais show high concentrations of male haplogroup I argued for a common origin (see maps in the file section); it turns out that the Ossetians are mainly male haplogroup G
http://en.wikipedia.org/wiki/Haplogroup_G_%28Y-DNA%29
http://en.wikipedia.org/wiki/Haplogroup_G_%28Y-DNA%29#Caucasus
http://www.members.cox.net/morebanks/MoreG2.html
which however is also a male Caucasus marker.
If I want to save a theory that Yazygi or Alans colonized large parts of Europe 'under cover' so to speak, I'd have to claim that the Alans/Ossetians received their high G percentage in the Caucasus. But that seems awkward (althouh since they have the highest G percentage of all groups there, plus that if I claim that the Alans were once haplogroup R
http://en.wikipedia.org/wiki/Haplogroup_R_%28Y-DNA%29
as the other Iranian steppe groups I would have no theory of cohesion with anyone in particular in Europe.
So I think I'll modify my conjecture to this: The Yazygi etc were mainly R with some G from early intermarriage (Vanir etc), but picked up someone else with haplogroup I in Tanais, which became dominant in their later travels.
Torsten