DNA Shows Early European Migrants Regularly Interbred with Neanderthals

When the first human migrants set foot in Europe, they interacted with Neanderthals already living in the continent around 45,000 years ago.

DNA discovered from human fossils from that period, considered the oldest known remains of humans in Europe, led to researchers to suggest that there was interbreeding between the Neanderthals and homo sapiens. Neanderthals were at this period on the brink of extinction. Interbreeding, the study said, has been more common than what was believed.

Study findings were published in Nature Ecology and Evolution (Initial Upper Palaeolithic humans in Europe had recent Neanderthal ancestry).

Genetic proof found in the new report show for the first time that distinct human populations arrived in Europe about 50,000 years ago. Neanderthals interbred with the migrants, guaranteeing that a number of their genes exist today in our DNA.

Fossil Yielded DNA from Neanderthals

Researchers retrieved the remains of three homo sapien individuals in the Bacho Kiro Cave. They said the remains yielded nuclear DNA that contained Neanderthal contributions of around three to four percent. This ancient DNA was taken from two bone fragments and a tooth. Radiocarbon dating showed the DNA was about 43,000 to 46,000 years ago. Late Stone Age stone tools were discovered in the same sediment as the fossils.

Bacho Karo individuals had Neanderthal ancestors, about five to seven generations back in their family bloodline, the study showed.

Additional evidence of interbreeding would be seen in a complete human skull that was recovered in 1950 in a cave in the Czech Republic. About two percent DNA genes from the fossil, which was identified as a female, also originated from Neanderthals, researchers said. Analysis of the fossil reveals that she lived about 45,000 years ago.

Fossils of homo sapiens in the Czech Republic and Bulgaria are not the first ones to show Neanderthal DNA in their genomes, but they could have been the oldest discovered. The extended Neanderthal DNA found in the eastern European woman could have been split into shorter segments in more recent human generations.

They suggest the woman lived around a hundred to a thousand years than earlier discovered 45,000-year-old Siberian man who carried 2.3 percent of Neanderthal genes. That discovery showed that interbreeding outside of Europe went back to around 60,000 years ago.

Another fossil from an early human in Romania, a man, who lived around 40,000 years ago likewise carried extended stretches of Neanderthal DNA, indicating he had Neanderthal ancestors four to six generations back.

Neanderthal DNA Remnants Still Exist Today

Neanderthals became extinct around 40,000 years ago, although the remnants of their genes still exist today. Currently, non-African people possess about two percent of Neanderthal DNA. Africans today carry a smaller amount of Neanderthal genes.

Bringing these studies together, they show that some of the early humans in Europe had an enduring impact on our DNA, while the remaining entrants reached genetic dead-ends. Humans in Bacho Kiro represent the newly ascertained ancient European population with genetic ties to present-day Native Americans and East Asians, not with Western Eurasians, though, the report further said.

Similar to the ancient Siberian and Romanian men, the fossils of the woman discovered in the Czech Republic had no genes to homo sapiens that lived about 40,000 years ago.

If homo sapiens interbred regularly as subsequent populations neared its extinction, then large numbers of later generations of humans took a surprising amount of DNA from a small population of Neanderthals, researchers said. After 40,000 years ago, more migrations of people with little or no Neanderthal ancestry entered Europe, and their arrival would further dilute Neanderthal DNA from the gene pool of humans.

Those new human entrants developed bone and stone tools and became the ancestors of Europeans today. Newly discovered DNA from about 35,000 homo sapien bone fragments in Bacho Kiro show a different constitution than those the earlier human migrants. The individual with the newly retrieved DNA passed on genes to subsequent populations in Western Asia and Europe, the researchers noted.