Are Slavs native to the Balkans?

Posted by samvarr@reddit | AskBalkans | View on Reddit | 141 comments

Are Slavs actually native to the Balkans, or did they mainly arrive during the early medieval migrations? And who exactly lived there before them?

The Balkans seem to have always been a mix of peoples Illyrians, Thracians, Greeks, Romans, Celts, and later Turkic groups like the Avars and Bulgars before and during the Slavic migrations of the 6th–7th centuries. I also read that the Slavs were able to settle much deeper into the Balkans partly because the Turkic Avars weakened Byzantine control in the region.

How much of modern Balkan populations comes from Slavic settlers vs assimilation of earlier native Balkan peoples?