Two important new papers appeared in Science today. In the first one (Brandt, Haak et al.), researchers compiled mtDNA results from 364 prehistoric central Europeans from the early Neolithic to the early Bronze Age, spanning about four millennia of history. Importantly they uncover not a smooth transition between early Neolithic farmers and modern Europeans, but a punctuated series of haplogroup frequency changes that cannot really be explained by genetic drift in a single European population evolving over time. Hopefully this kind of research can be repeated in other parts of the world, as it provides a way to see evolution and migration as it happens.
Earlier work has disproved the hypothesis that modern Europeans are simply "acculturated" hunter-gatherers, and this newer research disproves the idea that they are simply the descendants of early farmers, little modified since the beginning of the Neolithic.