I mean germanic people/vikings raided/ruled southern Europe. The Mediterranean Sea was hugely important for trade and civilization, throughout the ages. Athens was a french duchy for a couple centuries, ruled by francs. Alps is not as isolating as, the Sahara desert. You have navigable rivers like Danube and southern France with access to the Mediterranean sea.

Does your average norwegian have some greek dna? Maybe not. But ultimately everyone fucked everyone and people fucked people near them. And the Mediterranean Sea facilitated a lot of fucking, trading and conquering between the countries that had access to it.

It's like saying "the mongols never conquered Greece, therefore greeks dont have mongol dna". The mongols fucked with turkic people and turkic(turks) people fucked with greek people. So i am sure greeks have some mongol dna.

There is this funny video of turkish youtubers who did dna tests

https://www.youtube.com/watch?v=TStTmMCtgBk

And many of them have majority greek dna or a big part of greek dna.