And yet the Beaker phenomenon survived, because it was not directly associated with a particular ethnic group, but was an international trade network.
Agree concerning the middle and the end of the expansion
Another evidence of the pluriculturality of the Bell Beaker phenomenon is that there were very distinct types of Beaker pottery in Indo-European Central Europe (the cord-impressed types, such as the "All Over Corded") and the Megalithic Western Europe (the "Maritime" type, decorated with bands filled with impressions made with a comb or cord).
What is interesting is that apparently two styles were contemporaneous in the same places in Portugal – + one of the oldest BB sites in N-Portugal maybe from before 2800 BC showed only the « pointillé » dotted lines style- in other places (later?) the two styles coexisist in time NOT in place : the high fortified places (high classes) have the martitime one, the lower places which are the lower classes ones (peasants, fishers) have the « incisés » pottery – (at first the higher places were occupied by the preceding Chalcolithic people) –but in other sites again (still in Portugal), three styles cohabited at the same time, making the classical chronologic distinction between styles completely inaccurate -
It is not a coincidence that the Beaker phenomenon has been divided by archaeologists into several groups. People who made Maritime beakers were simply not the same ethnic group as those who made or used beakers in Central Europe. This is obvious from mtDNA samples we have from this period.
Here we're speaking about Bell Beakers = Vases Campaniformes (even if with diverse styles) not about every kind of Beaker (as, by instance, the Corded first beakers of a well indentified ethnic group)- that said I agree that the great superficy of the final BB phenomenon cannot be assigned to a single ethnic group, as the bigger number of us had agreed long before – the different well assigned BBs potteries seem different (and male mediated for the most) in a lot of places from the domestic potteries -
In German sites containing beakers we see clearly Indo-European lineages like H4a1, I1a1, T1a, U2e, U4c1 and W5a, mixed with earlier Neolithic of Mesolithic lineages (H1, H3, T2e, U5).
But in Spain, all the mtDNA lineages are in clear continuity with earlier Neolithic samples. Iberian beakers samples tested to date include H1, H3, H14, H20 (or L3), J, K, L1b, L2, L3a, T2, U, V and X.