This issue keeps appearing and re-appearing. It is perhaps due to a tendency of conflating spatial population expansions with the proliferation of descendants within a lineage. The two are not necessarily related. Genetic-only methods can pick up on the signal of common descent and population growth, but cannot do the same for the signal of spatial expansion. Whether this growth happens (i) in situ for a long time, and only lately becomes a spatial expansion, or (ii) at the same time as the spatial expansion, or indeed (iii) long after it, will result in coalescences that precede, coincide with, or follow the actual spatial expansion event.
It is difficult to see how Europe was being filled up for thousands of years by a population taking advantage of post-glacial warming conditions, and, yet, when we actually look at ancient DNA from Europeans who lived just before the advent of farming, they show little evidence of possessing (m)any of the lineages that had been supposedly expanding in Europe since the LGM.
SCIENTIFIC REPORTS doi:10.1038/srep00745
MtDNA analysis of global populations support that major population expansions began before Neolithic Time
Hong-Xiang Zheng et al.
Agriculture resulted in extensive population growths and human activities. However, whether major human expansions started after Neolithic Time still remained controversial. With the benefit of 1000 Genome Project, we were able to analyze a total of 910 samples from 11 populations in Africa, Europe and Americas. From these random samples, we identified the expansion lineages and reconstructed the historical demographic variations. In all the three continents, we found that most major lineage expansions (11 out of 15 star lineages in Africa, all autochthonous lineages in Europe and America) coalesced before the first appearance of agriculture. Furthermore, major population expansions were estimated after Last Glacial Maximum but before Neolithic Time, also corresponding to the result of major lineage expansions. Considering results in current and previous study, global mtDNA evidence showed that rising temperature after Last Glacial Maximum offered amiable environments and might be the most important factor for prehistorical human expansions.