The ancestry of modern Europeans has been traced back to a single founding group of early humans living in the north west of the continent about 35,000 years ago. Researchers analysed the DNA from 51 prehistoric Europeans to find migration patterns and population changes over thousands of years.

Fossil evidence shows early humans first entered Europe roughly 45,000 years ago. However, little is known about their genetic ancestry before the onset of agriculture, some 8,000 years ago. Between their arrival and agriculture, Europe saw the end of the last Ice Age. Ice sheets that had covered northern Europe and Scandinavia between 25,000 and 19,000 years ago began to retreat.

A team of scientists, led by Harvard's David Reich, has now carried out the most comprehensive analysis of early European DNA to date. Previously, genetic data on just four prehistoric Europeans was available. "Trying to represent this vast period of European history with just four samples is like trying to summarise a movie with four still images," Reich said.

Red Lady of El Mirón Cave
Lower jaw of the 19,000-year-old Red Lady of El Mirón Cave from northern Spain. Lawrence G. Straus

Using 51 samples, the team was able to build up a far more extensive view of the changes over time. Findings, published in Nature, showed there were two major population changes in Europe between 45,000 and 7,000 years ago. The upheavals reveal how the Ice Age impacted the migration of populations and modern Europeans came from one founding population that lived in north west Europe roughly 35,000 years ago.

This founding group was displaced, however. It was found to have been living in south west Europe 19,000 years ago. As the ice started retreating, this same group spread northwards and repopulated Europe.

Another massive upheaval took place 14,000 years ago, when populations from the south east, including Turkey and Greece, spread into Europe. Their arrival introduced a new genetic component into modern Europeans. "These results document how population turnover and migration have been recurring themes of European pre-history," the study said.

Reich added: "What we see is a population history that is no less complicated than that in the last 7,000 years, with multiple episodes of population replacement and immigration on a vast and dramatic scale, at a time when the climate was changing dramatically."