The Genetic History of Ice Age Europe

Analyses of ancient DNA from prehistoric humans paint a picture of dramatic population change in Europe from 45,000 to 7,000 years ago, according to a new study. The new genetic data reveal two big changes in prehistoric human populations that are closely linked to the end of the last Ice Age around 19,000 years ago.

Archeological studies have shown that modern humans swept into Europe about 45,000 years ago and caused the demise of the Neanderthals, indicated by the disappearance of Neanderthal tools in the archaeological record. The researchers also knew that during the Ice age - a long period of time that ended about 12,000 years ago, with its peak intensity between 25,000 and 19,000 years ago - glaciers covered Scandinavia and northern Europe all the way to northern France. As the ice sheets retreated beginning 19,000 years ago, prehistoric spread back into northern Europe.

But prior to this study, there were only four samples of prehistoric European modern humans 45,000 to 7000 years old for which genomic data were available, which made it all but impossible to understand how human populations migrated or evolved during this period. 

The genetic data show that, beginning 37,000 years ago, all Europeans come from a single founding population has some deep branches in different parts of Europe, one of which is represented by a specimen from Belgium. This branch seems to have been displaced in most parts of Europe 33,000 years ago, but around 19,000 years ago a population related to it re-expanded across Europe. Based on the earliest sample in which this ancestry is observed, it is plausible that this population expanded from the southwest, present-day Spain, after the Ice Age peaked.

The Study was an equal collaboration of David Reich's laboratory with the laboratories of Savante Paabo and Johannes Krause, which worked together to extract and analyze the DNA from these ancient bones. Ancient specimens are frequently contaminated with m-DNA, as well DNA from archaelogists or lab technicians who have have handled the specimens.