The ancient Greeks were probably a combination of the people who brought the Greek language there and the people there in Neolithic and "Early Helladic" (3rd millennium B.C.) times.
Any similarities between modern Greeks and modern Turks may arise from two things: (1) medieval Greek-speaking Christians in Asia Minor later becoming Turkish-speaking Muslims and (2) Christians of Turkey fleeing to Greece in the 1920s.
I'd be interested in seeing DNA studies of modern Greece. I would have thought it might be too sensitive a topic (as the modern Greeks would prefer to think they are 100% of Hellenic descent).
As recently as the 19th century, Albanian was widely spoken in rural areas of Greece.
Hah, I’ve heard that myself but I think it’s probably closer to around 5%. You don’t want to tell them that, however. As far as Indo-Europeans go, I believe a lot of them may have come from Armenia, but I don’t know. Unfortunately history was not very kind to those who stayed. They were the first to come up with iron working, I think. Asia Minor was actually a very interesting place until the Muslims formed their brutal empire and erased much of history.
There are two gaps in the mountain range that separates southern from northern Europe. The northern plains are unbroken except for the densely forested hills of Germany, which basically prevented Roman occupation. It was also the staging point for a lot of invasions, since the garden spot was close down in the Danube. My own family history occurred in the Volga, the largest basin to the north-east. Then in South Dakota due to the unfriendliness of a certain northern empire. Nasty business, that was.