Ancient human DNA reveals how Europeans avoided extinction 20,000 years ago

DNA extracted from the bones of over 350 people who lived tens of thousands of years ago has revealed previously unknown chapters of Europe’s prehistory. The new data identify the hunter-gatherer groups who lived before and after one of the continent’s worst catastrophes – the Last Glacial Maximum – when ice sheets were at their greatest extent 19,000-25,000 years ago.

Ice covered large parts of the mainly uninhabitable continent during that period. Scientists believe 100,000 people lived in western and central Europe before the big freeze. The arrival of the ice and its accompanying temperature drop decimated human populations, leaving only small isolated groups of about 50 people. For the ancient Europeans, it was a near-apocalyptic event.

A recent study in Nature presents new genetic data from 116 individuals from 14 countries. The study covers the arrival of the first Homo sapiens in Europe (about 45,000 years ago) until approximately 3,200 BC when people throughout the continent had settled into agricultural lifestyles. This change enabled civilization to flourish and ended the nomadic way of life unique to our species.

The first wave of Homo sapiens that arrived in Europe from Africa met the Neanderthals, the continent’s native human species. They crossbred with the Neanderthals and had children but mysteriously became extinct without leaving any genetic trace in the Europeans of today. Neanderthals also disappeared about 40,000 years ago for unknown reasons but did leave a few drops of DNA in present-day humans outside Africa.

The new study shows that before the glaciation, Europe was divided into two major lineages of Homo sapiens that descended from successive migratory waves. Groups with ancestors from western Russia lived in what is now Italy, Austria and the Czech Republic. Spain and France were dominated by other groups whose roots went back at least 35,000 years to present-day Belgium.

Refuge in the south

Scientists previously thought that humans migrated south en masse when glaciation began. The Pyrenees and the Alps functioned as ice barriers protecting people already living in the Iberian and Italian peninsulas and preventing others from migrating south. Genetic data now show that human populations became utterly extinct in Italy.

“It’s a brutal fact,” says Vanessa Villalba-Mouco, a Spanish molecular biologist at the Max Planck Institute for Evolutionary Anthropology in Germany. Villalba-Mouco, a study co-author, adds, “The population was completely replaced, and we still don’t know why it happened.”

Another recent study published in Nature Ecology and Evolution analyzed the remains of one of the only known survivors of the glaciation. Archaeologists found a single tooth from an adult male in the Malalmuerzo cave in Granada, southern Spain, beneath walls adorned with paintings of horses. The whiteness and good health of their teeth were distinctive features of those Europeans, as foods that cause tooth decay, like sweets and bread, had not yet been invented.

The analysis of these remains shows that this man lived 23,000 years ago, surviving the worst period of the last glaciation. The DNA indicates that he was related to the hunter-gatherers who lived before the cold arrived. More importantly, his genetic legacy survived the ice age and is still present in today’s Europeans, although significantly diluted after millennia of mixing and remixing. The remains of two other ice age survivors have been found in northern Spain and southern France.

“This work confirms that the Iberian Peninsula and southern France were the only known refuge for survivors of the last glaciation,” says geneticist Carles Lalueza-Fox, co-author of this second study with Villalba-Mouco. “We already knew from the remains unearthed on the Iberian Peninsula that it was the only liveable area for many animals, such as brown bears, hedgehogs, shrews and tree species, including oaks. Now we know that it enabled Europeans of the time to survive.”

Elegant prehistoric art

The tooth found in the Malalmuerzo cave yielded the genetics associated with the Solutrean culture. It is known for its advanced tool-making, spearheads and arrows, and artistic representations of animals and other uniquely European scenes. The genetic analysis revealed that this culture descended from earlier European Homo sapiens – the Aurignacian culture – who created some of the earliest and most elegant prehistoric art, such as the felines in France’s Chauvet cave.

The study confirmed the lack of contact between the Iberian Peninsula and North Africa, even though glaciation had narrowed the Strait of Gibraltar. After the Last Glacial Maximum, the inhabitants of the Iberian Peninsula left their refuge and began to populate the rest of Europe. A new human lineage with roots in the Balkans and the Anatolian peninsula in Turkey had emerged by then. They quickly repopulated Italy and spread throughout the rest of the continent until they became the new dominant lineage in Europe, the Magdalenian culture, renowned for their prehistoric cave paintings such as the Altamira Bison in northern Spain.

About 9,000 years ago, a new human upheaval occurred in Europe when migrants from Mesopotamia brought agriculture, livestock and a sedentary lifestyle. Many nomadic tribes of hunters mixed with the new immigrants and embraced their way of life. Others clung to their nomadic traditions and survived in smaller, isolated groups. DNA reconstructions illustrate the physical characteristics of the nomads that lived less than 14,000 years ago. The ones in southern Europe had dark skin and blue eyes, while those in the north were pale-skinned and dark-eyed.

Roberto Risch, a prehistorian from the Autonomous University of Barcelona, notes the significance of these two new studies, which provide insights into an era without written testimonies through stone tools, vessels, paintings and human remains. Advances in DNA analysis enable us to disprove theories and confirm others. “Most importantly, these studies show us that the humans of that time were basically like us. Faced with a climate change that happened quickly in a single generation, how some groups reacted and made social decisions determined their fate. Those who chose to stay put and deny what was happening disappeared,” said Risch.

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