Europe had a lot of demographic turnover because there were never many humans

Now things are coming into focus. Population dynamics and socio-spatial organization of the Aurignacian: Scalable quantitative demographic data for western and central Europe:

Demographic estimates are presented for the Aurignacian techno-complex (~42,000 to 33,000 y calBP) and discussed in the context of socio-spatial organization of hunter-gatherer populations. Results of the analytical approach applied estimate a mean of 1,500 persons (upper limit: 3,300; lower limit: 800) for western and central Europe. The temporal and spatial analysis indicates an increase of the population during the Aurignacian as well as marked regional differences in population size and density. Demographic increase and patterns of socio-spatial organization continue during the subsequent early Gravettian period.

If you read The genetic history of Ice Age Europe you know the very first modern humans to arrive in Europe didn’t leave a genetic footprint in future populations. And the impact of both the later Gravettian and the Magdalenian seems to have been marginal. The primary “hunter-gatherer” contribution to modern Europeans is through a group which expanded after ~15,000 BC.

In any case, there are two things that I observe in relation to the population estimates above. First, they aren’t that unreasonable for a large mammal which isn’t much of a primary consumer of plants. Second, such a small and fragmented population indicates that extinction is always a possibility. You can take a standard conservation biological view and just assume statistically that small fragmented groups are likely to extinct over enough generations. Or, you can point out that genetically such small breeding populations (remember that the genetic breeding effective population is always smaller than the census population) are likely to build up deleterious alleles, and that’s probably going to result in a decrease of long term fitness.

In other words, I think localized mutational meltdowns would be possible in this scenario.

The small populations during this period are not surprising. Many of the Neanderthal, Denisovan, and hunter-gatherer (e.g., the first WHG sample) populations had small sizes that led to homogeneity genetically and inbreeding. You see it in the homozygosity data and the runs of homozygosity. Ultimately, it was the larger population sizes due to agriculture which changed things in a fundamental sense.

This makes me wonder what was so advantageous about these marginal modern humans which allowed them to overwhelm and absorb the older Eurasian hominins?


18,000 years BC (the film)

Alpha, set 20,000 years ago in Europe, was apparently originally titled “Solutrean.” The change is probably for the best. It will come out next spring. I really hope that this movie is good and does well. It isn’t often that you have something which takes place during the Last Glacial Maximum.

The plot seems to reflect the what you might read in Pat Shipman’s The Invaders, but it’s about 20,000 years too late for her model to work. One of the major criticisms of the idea that dogs and modern humans operated as a team is that it seems way too early. But of late there have been suggestions that the date is earlier than we’d previous thought in relation to when dogs as we understand them arose: Ancient European dog genomes reveal continuity since the Early Neolithic. Here’s the relevant section: “By calibrating the mutation rate using our oldest dog, we narrow the timing of dog domestication to 20,000–40,000 years ago.”

Please note though that the divergence of the dog lineage from the ancestors of modern wolves is a distinct question and process from domestication as such as we understand it. Though it seems likely these events didn’t occur too far apart in time.