I think what this article is really saying is that the effective population size of Europeans might have dropped to as little as 30 after the LGM peak. If so, that's pretty close to a genetic precipice for most animals. In any case, it looks like there are more hunter-gatherer genomes on the way, including from Denmark and Switzerland, courtesy of Ron Pinhasi's team, which brought us the ancient Hungarian genomes last year (see here).
‘As an archaeologist and anthropologist, I was quite shocked to see how limited, how small the population numbers were. You know, shockingly small,’ said Prof. Pinhasi, based at University College Dublin, Ireland.
‘I think that what happened, it’s on a catastrophic level of demography for a long time in human evolution,’ he said.
The impacts of this are significant for understanding the origins of many Europeans today, as it is forcing researchers to reconsider models of human expansion and colonisation of the continent, as well as our genetic ancestry.
By analysing the genomes of human remains, the researchers are able to gather demographic data and clues to potential population sizes.
Prof. Pinhasi’s team has found that the genomes sequenced from hunter-gatherers from Hungary and Switzerland between 14 000 to 7500 years ago are very close to specimens from Denmark or Sweden from the same period.
These findings suggest that genetic diversity between inhabitants of most of western and central Europe after the ice age was very limited, indicating a major demographic bottleneck triggered by human isolation and extinction during the ice age.
‘We’re starting to be able to reconstruct the actual dynamics of migrations and colonisation of the continent by modern humans and that’s never been done before the genomic era,’ explained Prof. Pinhasi.
He believes that early humans crossed the continent in small groups that were cut off while the ice was at its peak, then successively dispersed and regrouped over thousands of years, with dwindling northern populations invigorated by humans arriving from the south, where the climate was better.
Source: Francesca Jenner, Ice-age Europeans roamed in small bands of fewer than 30, on brink of extinction, 26 March 2015, Horizon Magazine