I just stumbled upon a somewhat old but very interesting article on why population genetics has gone mad and leaned towards Neolithic replacement against all archaeological evidence. Why? Because they never cared at all about the archaeological evidence, not even about the genetic evidence that contradicted their own conclusions: they have been acting ideological all this time. Sadly enough.
Mark Pluciennik, Clash of Cultures? Archaeology and Genetics. Documenta Praehistorica 2006. Freely available PDF.
Worth a read, really.