It seems to be the consensus that I originated in Europe (all evidence points toward that), after it split from IJ, its father haplogroup. Since both I and J split from IJ, is it possible that when IJ split first, that it was into only J at first, and then later I in Europe?

In other words, when IJ split, it didn't necessarily split into I as well as J at the same time, correct? It was possible that it first split into J in the Middle East, but not I, but when carrier of IJ arrived in Europe, it then split into I as well, but not J?

Another thing: What samples do we have from Upper Paleolithic corpses of IJ in Europe? Do they predate I in Europe?