Well for starters I2a-Din apparently didn't exist when the IE's expanded into this area. Perhaps some antecedent I2a did (Verenic alias Heimdale reported elsewhere that he has had an "unofficial" communication from a Ukrainian archaeologist that aDna tests on a late Trypilian (non-IE) gravesite has revealed the presence of M-170-->P 37.2 there (nothing more specific). That would be interesting but not that conclusive. After all we know that the closest I2a to I2a-Din (I2a-Disles, now located principally in the British Isles) separated from their MCRA about 4,600 BCE We don't know where (it could easily have been in Germany). And we have no idea where the clade immediately ancestral to I2a-Din was when "Papa" was born. People should really try to grasp the elementary fact that all those millions and millions of contemporary I2a-Din got started from this Papa. Two Papas actually Papa-N who initiated his family ca. 300 BCE and Papa-S who did the same when Augustus ruled the Roman Empire. And it takes a while for families to expand. They don't "assimilate" others: that is a cultural/linguistic phenomenon. We're talking about genetic expansion.