Originally Posted by
FrankN
In fact, while pointing at the Heruli, I didn't want to rule out the Goths. Let's assume that Ia2-Din originally evolved somewhere on the upper Dniester, and from there initially, in small quantities, spread south-eastwards into Ukraine / Moldowa, and north-westwards into Eastern Poland & Slovakia. Let's furthermore assume that the I2a-Din S and I2a-Din N split already took place on the upper Dniester, with I2a-Din N moving rather to the south-east, and I2a-Din S moving more towards the north-west. The East-Germanic tribes (Bastarnae, Goths, Heruli etc.) would have picked up a bit of I2a-Din S on their way to the Black Sea, and quite a lot of I2a-Din N in Western Ukraine & Moldova. Their incursions into the eastern Balkans, but also their settlement in Moesia as Roman federates, would have brought I2a-Din there. The Bulgars (which I don't qualify as Slavs - we may have a definition problem here) picked up more of I2a-Din N on their way, and probably also served for a re-distribution of the Moesian pool that originated from 3rd / 4th century Roman settlement of East Germanics. Whoever followed them, whether already Slavs, still proto-Slavs, or another linguistic group that later adopted Slavonic, did the same.
I2a-Din S, in the meantime, would have been picked up by Dacians, Iaszyges, and later the Huns, and spread into the northern Pannonian basin. Some of it may already during Roman times have found its way to the southern Bank of the Danube, be it during the Marcomanni incursions, as mercenaries, or seeking refuge from the Huns. The Heruli come into the picture as they provide a plausible explanation for a substantial transfer of NE-Pannonian genes into Illyria and Dalmatia. Note in this respect that during Justinian's wars, while peace negotiations with the Ostrogoths were going on, a massive fleet mainly manned by Illyrian HerulI lay 2 years idle in Salona (just next to the islands of Hvar and Korcula which have extremely high I2a-Din concentrations). Of course, the Avars and then the Slavs should have provided for further gene transfer from NE-Pannonia, either directly or by inducing influx of refugees. But essentially, that would have been the icing on the cake rather than the main cause.
In short - I don't think you can attach a specific ethnic name, be it Sarmatians (Iaszyges), Dacians, Goths, Bastarnae, Heruli, Huns, Bulgars, Avars or Slavs, to the processes that brought I2a-Din to the Balkan. They all played their role.