This is a fascinating question and (last time I kept abreast of the literature, admittedly about 8 or 9 years ago now) seemed to be an open one. DNA evidence ca

This is a fascinating question and (last time I kept abreast of the literature, admittedly about 8 or 9 years ago now) seemed to be an open one. DNA evidence can only tell so much because it only hints at the spread of technologies, languages, or the "Neolithic Package" of domestication practices and tools that revolutionized European prehistory. This article seems to have a more up to date view than the work I was familiar with (Cavalli-Sforza's): http://arheologija.ff.uni-lj.si/documenta/pdf30/30richards.pdf http://arheologija.ff.uni-lj.si/documenta/pdf30/30richards.p...