I think it's still possible that R1b has been around in Europe since the Neolithic, and we've just failed to test the right Neolithic ancient DNA so far, but the patterns of R1b across Europe don't fit that hypothesis very well. I'd certainly be willing to revise my position if we found Neolithic Western European DNA with Y-DNA R1b.
I think it's quite possible that Beaker people were transmitted a lot of culture from Corded Ware (R1a) peoples, and that transmission could have even had a significant impact on their expansion, which is likely linked to R1b expansion (and possibly the transmission of IE into Western Europe). However, to describe the patterns today, I think the most likely explanation is "it's complicated"... I would be unsurprised if it ended up being the case that Beaker culture was I2a2 dominant, with R1b a minority that later expanded within it, for example. Haplogroup R has this tendency to displace other haplogroups in populations, which some have linked to high sperm count, so it's quite possible that that might be in play here, as well.
All said, I have yet to see anything that would correlate R1b to G2a, which we know is Neolithic. R1b almost certainly came after, which helps us formulate an answer to the question in the topic: the expansion that brought G2a was likely blocked against entering into the Basque area by existing Haplogroup I peoples, while the expansion of R1b into Europe likely had some advantage (genetic or cultural or maybe both) which allowed it to assimilate into and genetically dominate the existing population.[/QUOTE ]
That is the best answer on my question yet . But stil there is problem because Basque has 86% R1b , and that R1b had to pas tru West Europe (if it come with rest of R1b) , and it had to pick up some G2a like the rest of R1b did . I gues that reason for today Basque has less then 0,25% G2a is that old population ( I2a1) has very litle G2a , but also incoming population ( R1b) had to has very litle G2a , because they descendants are mayority today. You provided answer on first part of question , but second part is yet there.
Thanks for answer