Why is upper Europe so homogenous?

[Trouble]

From Celts to east Slavs, there appears to be no major difference in genes.


Sample Details Fit Map Anatolia Barcin N Baltic LVA HG Yamnaya RUS Samara
1 Dutch:Average 3.6143 Open Map 37.5 17.5 45
2 German:Average 2.8419 Open Map 40.83 17.5 41.67
3 Irish:Average 4.0674 Open Map 35.83 16.67 47.5
4 Polish:Average 4.5338 Open Map 36.67 23.33 40
5 Russian_Kursk:Average 5.1323 Open Map 32.5 22.5 45
6 Swedish:Average 3.6621 Open Map 34.17 21.67 44.17

[SharpFork]

I think it's a combination of the fact that there were few replacement events, basically 2, and one of those happened during the Copper and Bronze age and subsequently there was little input from outside this ENF-Steppe cline which would have disrupted the unity.

Edit: Also Southern Europe was also basically a cushion/buffer zone, it also was mostly ENF with Steppe and the only way it could have affected Northern Europe would be through a very big replacement or through high Iran neolithic input, but given the history that didn't happen and in actually Northern Europe pushed itself into the Balkans.

[Jana]

It's a plain with little to none physical barriers. Except western Scandinavia, you have endless open space from Atlantic coast to Kazakhstan. Southern Europe is separated from rest of mainland Europe by Alps, Pyrenees and to lesser extent, Balkan mountains. Hence greater genetic diversity and less free gene flow among southern Europeans, who were partly protected by mountain ranges from steppic invasions during bronze age.

https://i2.wp.com/clovisinstitute.org/wp-content/uploads/2018/01/NorthEuropeanplain.jpg?resize=600%2C497

[Voskos]

Population bottleneck I guess.Plus what Feiichy said.

[SharpFork]

It's a plain with little to none physical barriers. Except western Scandinavia, you have endless open space from Atlantic coast to Kazakhstan. Southern Europe is separated from rest of mainland Europe by Alps, Pyrenees and to lesser extent, Balkan mountains. Hence greater genetic diversity and less free gene flow among southern Europeans, who were partly protected by mountain ranges from steppic invasions during bronze age.

Geography definitely plays a role but I think in of itself doesn't explain most of the similarity, think about it, if the Mediterranean was populated in antiquity by Sub-Saharan Africans would Northern Europe have stayed as compact as it is? I think the fact that this ENF-extra WHG-Steppe mix goes quite beyond northern Europe helped the region being shielded from much evident outside influence.

Southern Europe by itself couldn't have massively changed the genetics of Northern Europe when big states started to appear there, given that at the most extreme excluding Greeks and Phoenciains you would be speaking of 70-80% ENF and 20-30% Steppe+WHG people.

Like I said Greeks and Phonecians were a possibility for such a shift but again that's why Southern Europe is a buffer zone, there was never any Greek, Arab or Punic political presence north of the Alps or Carpathians.