Le Neolithique nord-atlantique du Maroc: premier essai de chronolgie par le radiocarbone
Jean-Pierre Daugas, Jean-Paul Raynal, Aziz Ballouche, Serge Occhietti, Pierre Pichet, Jacque Evin, Jean-Pierre Texier et Andre Debenath.
C.R. Academy of Sciences Paris, t. 308, Serie II, p. 681-687, 1989 [Link]
Neolithic of north-atlantic Morocco: first radiocarbon chronology attempt
Abstract - Nice 14C dates, compared to previous data, are used to propose a chronological framework for the north Atlantic Neolithic of Morocco. The Cardial established late, from 5300 B.C., over a poorly-known autochtonous population, and spread to the south. The scarcely-evidenced Middle Neolithic followed, from 4500 B.C., with Saharian influences. Circa 3700 B.C., the upper Middle Neolithic expanded over the entire area studied, with a pottery industry of the Proto-Bell-Beakers type. The final phase of the Middle Neolithic was a favorable environment for the birth of local metallurgy. At about 2700-2500 B.C., it participated in the emergence of the Iberic Bell-Beakers civilization which would return its products to Morocco.
See also [Link]
Obviously this paper is about pottery decoration influences, not people or culture. Since the "Beaker package" is an international conglomeration of neat things from other cultures, the cultural origin of those 'things' means absolutely nothing. The Beaker culture also had several formative phases in Europe, and the culture or people did not exist before this because it is at its heart a synthesis of "the best of Europe" at that time.
At the same rate, it's not a bunch-o-cultures and its ethnicity, at least before our psychotic understanding, was not an open-membership organization. The Bell Beakers were a genuine people or group of peoples who were related to each other. They moved into the domains of other people and established themselves at the expense of others who often rejected their culture. So the genetic formulation of an ethnic core is absolutely valid. There's no reason to beat this to death with overly nuanced disagreements as I think we all understand that human mixture and identity is complex.
For all intents and purposes, the average Bell Beaker person in Europe will draw a majority of his heritage from the ethnic Corded Ware people of Northern Europe. I think we already started seeing this with the first genomes of the Mittel-Saale and the Elbe and culturally, this was always true. Regardless of how much localized Neolithic ancestry any Beaker may have, which is probably very substantial, almost all Beakerfolk can trace their common heritage to an ancestral denominator emanating from the general vicinity of Rhine.
Beakers have an additional ancestry that makes them distinct from Corded Ware people. This is probably indicated by the distinct Y-chromosome and possibly by some fringe elements of African ancestry. This likely comes from Southwest Europe, and given its history, Atlantic Morocco of the Middle Neolithic shouldn't be discounted.
Other scenarios are possible as well, but whatever happened it was born in circumstances unique to Europe.