The culture and language are from those who came from elsewhere but locals joined them and intermarried with them, so after a couple of centuries the DNA of the locals prevailed.
Which is why most English have Celtic DNA, not Anglo Saxon DNA, and most Hungarians have Slavic DNA.
Language and culture is not genetic.
Good point. I’ve often wondered why in some such cases like the etrand bulgarians the language of the conquered prevails, while in the case of Turkey and Hungary, the language of the conquerors prevailed.
Modern Hungarians have plenty of Slavic and Germanic DNA. The Hungarian government at different times invited settlers in to repopulate the country after various wars, famines, plagues, etc reduced the population.
Which is why most English have Celtic DNA, not Anglo Saxon DNA, and most Hungarians have Slavic DNA.
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My understanding is that the celts are originally from the black sea region. Sometime in the bronze age about 1500 bc —they moved into europe—for much of that period they had a trading network going that was centered around the Helvetii of Switzerland and bavaria. The trading network went as far as into England. The Celtic culture in europe was dominant even in places where there were few celts—as was the case in England. The genetics of the welch the Irish are more similar to some groups along the Atlantic fringe in spain and Portugal. But their languages is celtic.