Do you think I2a-Din is a surviving Paleo/Mesolithic Haplogroup from the Balkans in particular, though? Or just Paleo/Mesolithic in Europe as a whole? Because if it's just Paleo/Mesolithic in Europe outside of the Balkans, then the answer to "How did I2a-Din get to the Balkans?" seems to be "The Slavs," rather than a combination of two answers, don't you think?