After humans first migrated from Africa about 60,000 years ago, we started having sex with Neanderthals – a now extinct archaic but closely related species.
Scientists now claim to have the most accurate estimate yet of when this breeding period took place – and it’s more recent than we thought.
Two extensive studies, including analysis of skulls of ancient modern humans (Homo sapiens) in Europe and Asia, were conducted to establish the time period.
The results show that the two species began breeding together about 50,500 years ago and continued to do so for about 7,000 years, until the Neanderthals began to go extinct.
By comparison, previous estimates for the time of interbreeding ranged from 54,000 to 41,000 years ago.
Neanderthals, who lived in Europe and Asia, had large noses, a strong double-curved brow ridge, and relatively short and stocky bodies.
Meanwhile, modern humans (Homo sapiens) evolved in Africa, but migrated from the continent 60,000 to 70,000 years ago.
When we reached Europe and Asia and found Neanderthals, primitive sexual drives made the two species unable to resist each other, despite their physical differences.
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Neanderthals, who had already settled in Europe and Asia when Homo sapiens left Africa, had large noses, a strong double-curved brow ridge and relatively short and stocky bodies
The new findings were published by an international team of experts in two studies published in Nature And Science.
“These results give us a deeper insight into some of the first pioneers to settle in Europe,” said Professor Johannes Krause, co-author of the paper in Nature.
“They also indicate that modern human remains found outside Africa that are older than 50,000 years could not have been part of the common non-African population that interbred with Neanderthals.”
The scientific community already knows that Homo sapiens had sex with Neanderthals, because DNA from Neanderthals has been found in the genomes of modern humans.
In fact, most non-Africans today inherit one to two percent of their ancestry from Neanderthals.
Since then, the details of human-Neanderthal interactions have raised some of the most pressing questions in human evolutionary biology.
The Nature paper, led by experts from the Max Planck Institute for Evolutionary Anthropology (MPI-EVA) in Germany, looked at some of the oldest human genes from the skull of a woman named Zlatý kun, found in the Czech Republic.
They also examined bone fragments from an early human population in Ranis, Germany, about 140 miles away.
This image from the National Museum in Prague shows the skull of an early Homo sapien named Zlatý k, originally discovered in the Konprusy Caves of the Czech Republic
The artist’s image shows what Zlatý k might have looked like during her lifetime. She may have been one of the first Homo sapiens to mate with Neanderthals
They found fragments of Neanderthal DNA that placed the mating somewhere between 45,000 and 49,000 years ago.
Meanwhile, the Science article looked at 58 ancient genomes, sequenced from DNA found in modern human bones from across Eurasia, as well as contemporary human genomes.
It found that modern humans have exchanged genes with our sister species over a period of about 7,000 years, starting about 50,500 years ago.
The genome-based estimate is consistent with archaeological evidence that modern humans and Neanderthals lived side by side in Eurasia for between 6,000 and 7,000 years.
“The mixing period was quite complex and may have lasted a long time,” says Benjamin Peter, genomics researcher at MPI-EVA and co-author of the Science article.
‘Different groups may have separated over the period of 6,000 to 7,000 years, and some groups may have continued mixing for a longer period of time.’
The new dates also imply that the initial migration of modern humans from Africa to Eurasia was effectively over 43,500 years ago.
This model in the Basel Natural History Museum shows a Neanderthal female. Despite going extinct about 40,000 years ago, Neanderthal genes are still found in humans
Neanderthals were an early relative of humans who went extinct about 40,000 years ago, although their time on this planet overlapped with that of modern humans (homo sapiens). The photo shows a recreation of a Neanderthal woman
Researchers think Neanderthal genes related to immunity and metabolism may have helped early humans survive and thrive outside Africa.
A 2020 study found that the two species could easily produce “fertile and healthy” offspring because they were genetically similar.
In the biological world, many animals are able to break the species barrier and interbreed with each other and produce healthy offspring, but it is rare for the offspring to be fertile.
The Neanderthals became extinct about 40,000 years ago.
The reasons for their demise vary, but experts have suggested that interbreeding, climate change and violent clashes with humans may be the cause.
Our genetic code also contains echoes of another, slightly more mysterious group of extinct human relatives, the Denisovans, who diverged from Neanderthals.
Less is known about the Denisovans, a population of early humans who lived in Asia at least 80,000 years ago and were also distantly related to Neanderthals.
Denisovans also bred with humans about 50,000 years ago, meaning the DNA of early hominids survives today.