Modern humans have been present in Europe for at least the last 45,000 years. Even when massive ice sheets crept south, covering much of the continent around 20,000 years ago, some people still managed to cling on to existence in the harsh environment. But how these changing environmental conditions influenced the early European populations, especially during this period when humans took their first steps into Europe, has remained somewhat of a mystery.

Now, research published in Nature has revealed how migration and population fluxes have influenced the genetic make-up of Europeans. The team of scientists found that the earliest settlers of the continent contributed very little to the gene pool. This is in contrast to a wave of modern humans migrating into Europe around 35,000 years ago, who are thought to have been members of the Aurignacian culture, and to which all modern-day Europeans can trace their ancestry. 

The researchers conducted genetic analysis on 51 prehistoric European modern human remains dating to between 45,000 and 7,000 years ago. In addition to the fact that these early pioneers left little genetic history behind, the Aurignacian people that replaced them were later displaced themselves by another group known as the Gravettian culture. But intriguingly, the researchers found that some people from the original founding Aurignacian people persisted in southwest Europe, and expanded again across the rest of the continent after the ice retreated following the last glacial maximum around 19,000 years ago.

The study was also able to provide an insight into the relationship of early modern humans and Neanderthals, who shared the continent with them for a few thousand years until their extinction around 40,000 years ago. The researchers found that modern human remains started containing around 3 to 6 percent Neanderthal ancestry, and gradually decreased to the current level of around 2 percent. This is consistent with the early interbreeding that is thought to have happened between the species before the Neanderthals went extinct.

The results of the study show just how complex and convoluted the ebb and flow of early human populations across the European continent actually were. Not only that, but it also highlights how despite humans having existed in Europe for tens of thousands of years, the earliest colonizers failed to leave their genetic trace, while that of the Neanderthals slowly diminished. 

^{Image in text: Reconstruction of what early human colonizers of Europe may have looked like. Stefano Ricci}