In the comments below someone asked if the model Bryan Sykes’ outlined in Seven Daughters of Eve (and later Saxons, Vikings, and Celts), that modern Britons descend predominantly from the Paleolithic stock which repopulated the island in the wake of the end of the last Ice Age (or fled Doggerland), is still tenable. I don’t think so much. First, the tripartite origin of modern Northern Europeans probably puts more of an emphasis on migration in the Western regions of the continent. Yes, in many groups the ancestry which derives from the small populations which followed as the glaciers retreated is overall predominant (that is, somewhat more than 50%). But that is distinct from the idea that the proportion of ancestry from hunter-gatherers in any given area, such as Britain, is from indigenous hunter-gatherers long resident. What I’m getting at is that socio-cultural groups, such as “Early European Farmers” (EFF) and the Yamna, which contributed a great deal of ancestry to modern people are themselves in origin compounds of disparate elements. Because of the seeming homogeneity of European hunter-gatherers, likely due to a Pleistocene bottleneck and then a rapid range expansion from small founder groups, earlier methods of aligning mtDNA and Y haplogroups may have misled because of the lack of power to distinguish between extremely close lineages (European hunter-gatherers are almost all mtDNA group U and predominantly Y group I). Therefore the predominant Paleolithic ancestry across Northern Europe may actually be a function of a few discrete pulse admixture events. Subsequently demographically successful groups then carried this ancestry where they went, possibly replacing natives in totality.

I grant that this is speculative and not certain. For example, one assumption I’m making is that the density of hunter-gatherers was rather low across Europe. But clearly there were marine environments where they seem to have been thicker on the ground, particular zones where agriculturalists seem to simply stop their advance abruptly The ultimate answer will probably be through ancestry deconvolution methods. Basically, looking at the distribution of lengths of distinct ancestral elements, and seeing which model the empirical patterns fit. If I’m correct, then the distribution of lengths for hunter-gatherer ancestry in Northern Europe will be narrower than if you had a scenario of continuous regional expansion. It’s certain that someone is working on this.

Genetically the two scenarios don’t make that much of a difference, because European hunter-gatherers were probably a very homogeneous bunch (though this might be generally true for Eurasian hominins, as Neandertals and the Denisovan sample also exhibit low genetic diversity in comparison to modern populations). But anthropologically it is critical, because it fleshes out the processes of potential cultural change and turnover in the transition between societies and modes of production.