Dienekes has a nice post about the relation of Neolithic Europeans, migration models, and how anthropological views of migration have changed over the last century. He starts with Carleton Coon, although he might have gone back substantially earlier.
I'll note that Franz Weidenreich, writing shortly after the cited work by Coon, had a very different view of the essential data underlying migrationism, especially the trend toward brachycephalization.
Anyway, he traces the move from full-on folk migration to "demic diffusion" and "acculturation" models, back through recent genetic work that suggests some substantial genetic replacement -- either by means of selection or folk migration/demographic expansion.
We have come full circle. Once again, Paleolithic Europeans assume the status of survivors, as their typical lineages are observed in a small minority of modern Europeans. The evidence for widespread acculturation of European hunter-gatherers or their significant genetic contribution to incoming farmers along a wave of advance is just not there. Hunters and farmers possessed distinctive gene pools, and farmers expanded with barely a trace of absorption of hunter gene pools.
With the India genetics paper from a couple of weeks ago, I think we're seeing that recent large-scale genetic changes are not limited to Europe.
