Celts to Anglo-Saxons, in light of updated assumptions

Over the past week there have been three posts which I've put up which are related. Two of them have a straightforward relation, Britons, English, Germans, and collective action and Britons, English, and Dutch. But the third might not seem related to the other two, We stand on the shoulders of cultural giants, but it is. When we talk about things such as the spread of language through "elite emulation" or "population replacement" they're rather vague catchall terms. We don't decompose them mechanistically into their components to explore whether they can explain what they purport to explain. Rather, we take these phenomena for granted in a very simplistic black box fashion. We know what they're describing on the face of it. "We" here means people without a background in sociolinguistics, obviously. To give an example of the pitfall of this method, in much of Rodney Stark's work on sociology of ...