What is the problem in the balkans?

The ethnogenesis of the Illyrians remains a problem for prehistorians, however the consensus is that the ethnic ancestors of the Illyrians, the Proto-Illyrians, branched off from the main Proto-Indo-European trunk before the Iron Age. Current theories of Illyrian origin are based on ancient remnants of material culture found in the area, but archaeological remains alone have so far proven insufficient for a definite answer to the question of the Illyrian ethnogenesis.