After humans first migrated out of Africa about 60,000 years ago, we started having sex with Neanderthals – a now extinct archaic but closely-related species.
Now, scientists claim to have the most accurate estimate yet of when this breeding period took place – and it’s more recently than we thought.
Two comprehensive studies, including analysis of skulls of ancient modern humans (Homo sapiens) in Europe and Asia, were performed to pinpoint the time period.
Results show the two species started to breed with each other about 50,500 years ago and continued to do so for about 7,000 years, until Neanderthals began to die out.
For comparison, previous estimates for the time of interbreeding ranged from 54,000 to 41,000 years ago.
Neanderthals, who were living in Europe and Asia, had large noses, strong double-arched brow ridge and relatively short and stocky bodies.
Meanwhile, modern humans (Homo sapiens) evolved in Africa but migrated out of the continent 60,000 to 70,000 years ago.
When we reached Europe and Asia and found the Neanderthals, primitive sexual urges meant the two species couldn’t resist each other, despite the physical differences.
Neanderthals, who were already established in Europe and Asia when homo sapiens left Africa, had large noses, strong double-arched brow ridge and relatively short and stocky bodies
The new findings have been published by an international team of experts in two studies, published in Nature and Science.
‘These results provide us with a deeper understanding of some of the earliest pioneers that settled in Europe,’ said Professor Johannes Krause, co-author of the Nature paper.
‘They also indicate that any 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 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 per cent of their ancestry from Neanderthals.
Since then, the details of human-Neanderthal interactions have offered some of the most pressing questions in human evolutionary biology.
The Nature paper, led by experts at 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, called Zlatý kun, found in the Czech Republic.
They also examined bone fragments from an early human population in Ranis, Germany, about 140 miles (230 kilometers) away.
This image provided by National Museum, Prague shows the skull of an early Homo sapien called Zlatý k, originally discovered in the Konprusy caves of the Czech Republic
Artist’s depiction shows what Zlatý k might have looked like during her lifetime. She may have been among some of the first Homo sapiens to have mated with Neanderthals
They found snippets of Neanderthal DNA that placed the mating at somewhere between 45,000 and 49,000 years ago.
Meanwhile, the Science paper looked at 58 ancient genomes sequenced from DNA found in modern human bones from around Eurasia, as well as modern-day human genomes.
It found modern humans swapped genes with our sister species in a roughly 7,000-year period starting around 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 period of mixing was quite complex and may have taken a long time,’ said Benjamin Peter, genomics researcher at MPI-EVA and co-author of the Science paper.
‘Different groups could have separated during the 6,000- to 7,000-year period 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 into Eurasia was basically over by 43,500 years ago.
This model at the Natural History Museum of Basel depicts a Neanderthal female. Despite going extinct around 40,000 years ago, the genes of Neanderthals are still found in humans today
Neanderthals were an early relative of humans who died out around 40,000 years ago, although their time on this planet did overlap with modern humans (homo sapiens). Pictured, a recreation of a Neanderthal woman
Researchers think Neanderthal genes related to immunity and metabolism that may have helped early humans survive and thrive outside of Africa.
A 2020 study found the two species could produce ‘fertile and healthy’ offspring with ease because they were genetically alike.
In the biological world, lots of animals are able to breach the species barrier and interbreed and produce healthy offspring, but it is rare for the offspring to be fertile.
Neanderthals went extinct around 40,000 years ago.
Reasons for their demise vary, but experts have suggested interbreeding, climate change and violent clashes with humans may be to blame.
Our genetic code also contains echoes from another slightly more mysterious group of extinct human relatives called 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 around 50,000 years ago, meaning the DNA of the early hominids survives today.
