For Several Millennia, Neanderthals And Modern Humans Actually Interbred
For several millennia, Neanderthals and modern humans interbred shortly after all non-African ancestors moved into Eurasia.
While these Homo sapiens populations gained an evolutionary edge from the new Neanderthal genes, not all who interacted with Neanderthals managed to survive, and some human lineages ultimately died out.
A team of researchers analyzed seven genomes from H. sapiens who lived in Europe about 45,000 years ago. They determined that Neanderthal DNA in all ancient and present-day non-Africans originated from a “pulse” of interbreeding that occurred around 45,000 to 49,000 years ago.
The research team examined the genomes of six skeletons that were found at a site called Ilsenhöhle in Ranis, Germany, and a seventh skeleton from the site of Zlatý kůň in the Czech Republic.
The individual from the Czech Republic was distantly related to the people from Germany. This meant they all descended from the same population that moved from Africa to Europe.
The team also discovered that the two groups from Germany and the Czech Republic branched off pretty quickly from the original population that moved out of Africa.
The split occurred just after the original population interbred with Neanderthals. Soon, the lineage from Germany and the Czech Republic died out.
Most modern non-African humans have around one percent to three percent of Neanderthal DNA in their genomes, so the researchers concluded that these people are likely descendants of one big wave of people who left Africa and mated with Neanderthals.
As a result, all the modern human remains outside of Africa that are over 50,000 years old are actually “evolutionary dead ends,” not ancestors of modern-day people, according to Arev Sümer, the lead author of the study and an archaeogeneticist at the Max Planck Institute for Evolutionary Anthropology.
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Another study of the genomes of 334 modern humans from around the world figured out when humans and Neanderthals mated and which Neanderthal genes were beneficial to humans.
The researchers of the second study found evidence that suggested only a handful of Neanderthal groups supplied the DNA seen in modern humans.
They questioned when the interbreeding happened, as only a small number of Neanderthals contributed their DNA to modern humans.
After scanning the genomes, they found that Neanderthals and modern humans interbred over several generations for approximately 7,000 years.
The genome regions in modern humans related to metabolism, immunity, and skin pigmentation contained significant amounts of Neanderthal DNA.
“Many of these genes may have been immediately beneficial to modern humans as they encountered new environmental pressures outside Africa,” wrote the researchers.
Although scientists now know more than ever about early interactions between H. sapiens and Neanderthals, many questions still remain.
Further analysis of ancient genomes is needed to gain a clearer understanding of how humans spread across Eurasia and the Pacific region.
The studies were published in Nature and Science.
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