As I have mentioned before, the mtDNA of European hunter-gathers seems to be very different from that of modern Europeans. The ancient European mtDNA pool was about 80% U5b – today that lineage is typically found at 10% frequency or lower, except in northern Scandinavia. Haplogroup H, currently the most common in Europe, has never been found in early Neolithic or pre-Neolithic Europeans. Less has been done with ancient Y-chromosomal DNA, but the data we have suggests that the lineages that were common in the early Neolithic and pre-Neolithic are rare today. R1b is the most common y-chromosomal haplotype today in Western Europe: it has never been found in Neolithic or pre-Neolithic Europeans. We find G2 in the early Neolithic: today it is rare, except in Sardinia and some mountainous regions of Italy and Sicily. It sure looks as if we’re talking near-complete replacement – which means that the historical process involved does not look much like a peaceful, diffusion-style range expansion. Perhaps more like the Death Song of Ragnar Lodbrok, which abounds in phrases like this: “Where the swords were whining while they sundered helmets”
Interestingly, there is a very similar pattern in canine mtDNA. Today Europeans dogs fall into four haplotypes: A (70%), B(16%), C (6%), and D(8%). But back in the day, it seems that the overwhelming majority of dogs (88%) were type C, 12% were in group A, while B and D have not been detected at all.
The ancestors of today’s Europeans didn’t fool around.