Sex between humans and Neanderthals was much more common than thought

Thousands of years ago, the lives of two different kinds of people were forever changed by two distinctly different events.

During the transition from the Middle to the Paleolithic, anatomically modern humans – homo sapiens (that’s us) – started migrating through Eurasia. Neanderthals, meanwhile, began to disappear.

“There has been intense debate for a long time about exactly how these processes went,” Mateja Hajdinjak tells InverseHajdinjak is an associate researcher at the Max Planck Institute for Evolutionary Anthropology and an expert in ancient genomics.

A study written by Hajdinjak and published Wednesday in the journal Nature – in addition to another old people study, also published Wednesday in Nature – finally provides much-needed insight into what happened nearly 45,000 to 35,000 years ago.

Together, the separate teams present the evidence of the elder Homo sapien remains ever found in Europe. Genetic analyzes of these remains reveal a relationship between these ancient individuals and modern humans – and suggest that mating between modern humans and Neanderthals was dramatically more common than scientists previously thought.

The background – Here’s what we do know:

  • Modern humans appeared in Europe at least 45,000 years ago
  • Neanderthals disappeared from Europe about 40,000 years ago

What is not well understood is the magnitude of the interactions between Neanderthals and modern humans, and how exactly these early Europeans are part of the larger story of human expansion beyond Africa.

Adding to the riddle is the rarity of it Homo sapien continues to date from this period. Even if a scientist discovers a bone or tooth that belongs to an ancient human, that doesn’t necessarily mean it’s a useful specimen. After the death of an organism, the DNA is broken down, “it shortens over time and modifications accumulate,” explains Hajdinjak.

After tens of thousands of years of degradation, scientists are excited when a specimen has even a small amount of DNA left to analyze.

What’s new – Five of the seven ancient people found in the Bacho Kiro cave in Bulgaria are very, very old. Radiocarbon dating performed by Hajcdinjak and his colleagues suggests that these people existed between 45,930 and 42,580 years ago.

This makes them “the oldest Upper Paleolithic modern humans recovered in Europe,” the research team writes.

The other Nature study, also conducted by researchers at the Max Planck Institute, presents a genome sequence extracted from a skull that belonged to a female Homo sapien who lived in today’s Czech Republic (Czech Republic in the study). In this case, it is the length of the Neanderthal segments in her genome that suggests her age: at least 45,000 years.

All of these ancient people represent some of the earliest homo sapiens in Eurasia after migration from Africa.

Both studies show how closely the lives of these individuals were intertwined with the fate of the Neanderthals. At least 3 percent of the woman’s DNA found in the Czech Republic was Neanderthal. Meanwhile, the genomes of three of the ancient people found in Bacho Kiro Cave suggest that they had Neanderthal ancestors in their family tree just a few generations back.

This suggests that mixing between humans and Neanderthals was more common than previously thought. Before that, evidence of relatively recent Neanderthal ancestry came down to a 40,000-year-old human found in Romania. His DNA suggested to the researchers that “Neanderthals and modern humans intermingled more than once and in Europe and later,” says Hajdinjaks. Besides this individual, the best evidence of NeanderthalHomo sapien mating was in the DNA of living people.

“Crucial is all IUP [Initial Upper Paleolithic] Individuals from the Bacho Kiro Cave have Neanderthals ancestors from about 5 to 7 generations before they lived, suggesting that the admixture between these first humans in Europe and Neanderthals was common, ”says Hajdinjak.

The big takeaway – Hajdinjak and colleagues were also able to investigate the relationship between the Bacho Kiro Cave individuals and later human populations.

A scientist is working on the excavation of the Bacho Kiro cave. Tsenka Tsanova, MPI-EVA Leipzig

By comparing the genomes of these individuals with other ancient and current people, it was found that these individuals are more closely related to people who contributed ancestors to East Asians, rather than to West Eurasians. This does not mean that it was precisely these individuals who contributed to later populations in East Asia, but it does mean that they are closely related to the people who did so.

Ultimately, the findings build on a basic human truth: we move. We are moving a lot of and we always have. The individuals of the Bacho Kiro Cave contributed to later populations of Asian ancestry, but it can be assumed that other ancient individuals contributed to the DNA of later Eurasians and Europeans. These ancient peoples met and mated with other ancient human species and kept scattering like ripples in a pond.

With each new discovery, we understand better what it means to be human.

“I’ve always been fascinated by human prehistory where no written records exist,” says Hajdinjak. “The ancient DNA provides us with an invaluable window into the past – literally as our own time machine.”

Bacho Kiro Cave abstract: Modern humans appeared in Europe at least 45,000 years ago, but the extent of their interactions with Neanderthals, which disappeared about 40,000 years ago, and their relationship to the wider expansion of modern humans outside Africa are poorly understood. Here we present genome-wide data from three individuals dated between 45,930 and 42,580 years ago from Bacho Kiro Cave, Bulgaria. They are the earliest modern people of the Late Pleistocene known to have been recovered in Europe so far and were found in association with a first collection of artifacts from the Upper Paleolithic. In contrast to two previously studied individuals of similar ages from Romania and Siberia who have not demonstrably contributed to later populations, these individuals are more closely related to current and ancient populations in East Asia and America than to later West Eurasian populations. This indicates that they belonged to a modern human migration to Europe previously unknown from the genetic data, and provides evidence that there was at least some continuity between the earliest modern humans in Europe and later humans in Eurasia. In addition, we find that all three individuals had Neanderthal ancestors a few generations back in their family histories, confirming that the first European modern humans mixed with Neanderthals and suggests that such mixing could have been common.

Old skull abstract: Modern humans expanded to Eurasia more than 40,000 years ago after their spread from Africa. These Indo-Asians carried ~ 2-3% Neanderthal ancestry in their genomes, originating from intermixing with Neanderthals that occurred sometime between 50,000 and 60,000 years ago, probably in the Middle East. In Europe, modern human expansion preceded the disappearance of Neanderthals from the fossil record by 3,000 to 5,000 years. The genetic makeup of the first Europeans to colonize the continent more than 40,000 years ago remains poorly understood as few specimens have been studied. Here we analyze a genome generated from the skull of a female individual from Zlatý kůň, Czech Republic. We found that she belonged to a population that seems to have contributed genetically neither to later Europeans nor to Asians. Its genome carries ~ 3% Neanderthal ancestry, comparable to that of other Paleolithic hunter-gatherers. However, the length of the Neanderthal segments is longer than that observed in the currently oldest modern human genome of the ~ 45,000-year-old Ust’-Ishim person from Siberia, suggesting that this person from Zlatý kůň is one of the earliest Eurasian inhabitants . after the expansion from Africa.