Towards the end of the last Ice Age, there was a major shift in the human population of Europe. A massive influx of people came into the continent, replacing the native hunter-gatherers and changing the genetic profile for all of Europe.

“We uncovered a completely unknown chapter of human history,” said lead author Johannes Krause in a statement. The findings were published in Current Biology this week.

While there have been plenty of studies looking into the movement of people around Europe, they have tended to focus on the last 10,000 years, with less research into older remains. “There has been a real lack of genetic data from this time period, so consequently we knew very little about the population structure or dynamics of the first modern humans in Europe,” explains Krause. This is partly because human remains from earlier than this period are few and far between.

But this new study was able to analyze the mitochondrial DNA, which is only passed on from mothers, of 55 human remains from 35,000 to 7,000 years ago. They were from individuals who lived in Italy, Germany, France, Belgium, the Czech Republic and Romania. What they found was that around 14,500 years ago, there was a major upheaval in Europe, when the continent was coming out of the Last Glacial Maximum.

During the peak of the Ice Age, the hunter-gatherer inhabitants of Europe were pushed further and further south, until they survived in just a few pockets. But when the climate changed, and things warmed up again, the original inhabitants were replaced by a different group of hunter-gatherers. Where exactly these people came from is still unknown, although the researchers suspect that they probably came from southeastern Europe.

The new study also helps to explain a long-standing puzzle that has divided opinion among those who have studied the movement of our species around the globe. This has revolved around the prevalence of certain genetic haplotypes, or genetic variations, found in different populations across the world. In Asians, Australasians and Native Americans, the M haplotype is prevalent, but it is incredibly rare in Europeans, who tend to carry the N haplotype instead. This has led some to believe that around 55,000 years ago, there were two separate dispersal events from Africa – one that gave rise to the M group in the east, and another that went to Europe and gave rise to the N group.

But when analyzing the genetics of the ancient European hunter-gatherers, the researchers found something interesting: Seven of the individuals had the M haplotype. The researchers suggest this variation might have been common across ancient Europe, until the last Ice Age pushed the population south and reduced their numbers. This decreased the haplotype's incidence within the region, and implies that there was indeed only one dispersal event from Africa. When the subsequent influx then occurred around 14,000 years ago, the genetic haplotype was simply lost from the general population.

^{Image in text: This skull from the Czech Republic is one of the first peoples to have inhabited Europe. Martin Frouz}