A groundbreaking new study suggests that Neanderthals and modern humans interbred more recently than previously believed, reshaping our understanding of human evolution. According to the research, these two closely related species mated as recently as 50,000 years ago, long after humans first migrated out of Africa around 60,000 years ago.
A Revised Timeline of Human-Neanderthal Interbreeding
Scientists now claim to have the most precise estimate yet of when this interbreeding occurred. Two comprehensive studies—one published in Nature and the other in Science —analyzed ancient human skulls and genomes from Europe and Asia to pinpoint the timeline.
The findings reveal that humans and Neanderthals began interbreeding approximately 50,500 years ago and continued to do so for about 7,000 years, until Neanderthals began to go extinct.
Previous estimates had placed the interbreeding period between 54,000 and 41,000 years ago, but the new research narrows this window significantly. This revised timeline provides fresh insights into the interactions between these two species and their eventual coexistence in Eurasia.
Physical Differences Didn’t Stop Attraction
Neanderthals, who inhabited Europe and Asia before going extinct around 40,000 years ago, were physically distinct from modern humans. They had large noses, prominent brow ridges, and stocky builds.
Modern humans (Homo sapiens ), on the other hand, evolved in Africa and began migrating out of the continent between 60,000 and 70,000 years ago. Despite their physical differences, the two species were drawn to each other when they encountered one another in Europe and Asia, driven by primitive sexual urges.
Genetic Evidence of Intermixing
The scientific community has long known that humans and Neanderthals interbred because Neanderthal DNA is present in the genomes of non-African populations today. Most people of non-African descent carry between 1% and 2% of Neanderthal ancestry.
This genetic legacy has been linked to traits such as immunity and metabolism, which may have helped early humans adapt to life outside Africa.
The Nature study, led by researchers at the Max Planck Institute for Evolutionary Anthropology (MPI-EVA) in Germany, analyzed some of the oldest known human genomes, including DNA from the skull of a woman named Zlatý kůň , discovered in the Czech Republic, and bone fragments from an early human population in Ranis, Germany.
These analyses revealed traces of Neanderthal DNA dating the interbreeding to between 45,000 and 49,000 years ago.
Meanwhile, the Science paper examined 58 ancient genomes sequenced from modern human bones found across Eurasia, along with contemporary human genomes.
This study concluded that humans and Neanderthals exchanged genes over a roughly 7,000-year period starting around 50,500 years ago. This timeline aligns with archaeological evidence showing that the two species coexisted in Eurasia for 6,000 to 7,000 years.
A Complex Period of Mixing
Benjamin Peter, a genomics researcher at MPI-EVA and co-author of the Science paper, explained that the period of interbreeding was likely complex and prolonged. “Different groups could have separated during the 6,000- to 7,000-year period, and some groups may have continued mixing for a longer time,” he said. This suggests that interbreeding wasn’t a single event but rather a series of encounters spread over millennia.
The new findings also imply that the initial migration of modern humans from Africa into Eurasia was largely complete by 43,500 years ago. By this time, humans had established themselves in Europe and Asia, interacting with Neanderthals and leaving behind a genetic legacy that persists to this day.
Why Did Neanderthals Go Extinct?
While interbreeding enriched the human genome, it may have contributed to the decline of Neanderthals. Other factors, such as climate change and violent conflicts with humans, have also been proposed as reasons for their extinction around 40,000 years ago. However, the exact cause remains a subject of debate.
Denisovans: Another Piece of the Puzzle
In addition to Neanderthals, humans also interbred with another group of extinct hominins known as Denisovans. Though less is known about them, Denisovans were distantly related to Neanderthals and lived in Asia at least 80,000 years ago. Like Neanderthals, they left traces of their DNA in modern human populations, particularly in Melanesians and Aboriginal Australians.
Implications for Human Evolution
Professor Johannes Krause, co-author of the Nature paper, emphasized the significance of these findings. “These results provide us with a deeper understanding of some of the earliest pioneers that settled in Europe,” he said. “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 studies highlight the intricate and dynamic nature of human evolution, underscoring how interbreeding with other hominin species shaped our genetic makeup. Far from being isolated events, these encounters were integral to the survival and success of modern humans as they spread across the globe.
THE DENISOVANS EXPLAINED
Who were they?
The Denisovans are an extinct species of human that appear to have lived in Siberia and even down as far as southeast Asia.
The individuals belonged to a genetically distinct group of humans that were distantly related to Neanderthals but even more distantly related to us.
Although remains of these mysterious early humans have mostly been discovered at the Denisova Cave in the Altai Mountains in Siberia, DNA analysis has shown the ancient people were widespread across Asia.
Scientists were able to analyse DNA from a tooth and from a finger bone excavated in the Denisova cave in southern Siberia.
The discovery was described as ‘nothing short of sensational.’
In 2020, scientists reported Denisovan DNA in the Baishiya Karst Cave in Tibet.
This discovery marked the first time Denisovan DNA had been recovered from a location that is outside Denisova Cave.
How widespread were they?
Researchers are now beginning to find out just how big a part they played in our history.
DNA from these early humans has been found in the genomes of modern humans over a wide area of Asia, suggesting they once covered a vast range.
They are thought to have been a sister species of the Neanderthals, who lived in western Asia and Europe at around the same time.
The two species appear to have separated from a common ancestor around 200,000 years ago, while they split from the modern human Homo sapien lineage around 600,000 years ago.
Last year researchers even claimed they could have been the first to reach Australia.
Aboriginal people in Australia contain both Neanderthal DNA, as do most humans, and Denisovan DNA.
This latter genetic trace is present in Aboriginal people at the present day in much greater quantities than any other people around the world.
How advanced were they?
Bone and ivory beads found in the Denisova Cave were discovered in the same sediment layers as the Denisovan fossils, leading to suggestions they had sophisticated tools and jewellery.
Professor Chris Stringer, an anthropologist at the Natural History Museum in London, said: ‘Layer 11 in the cave contained a Denisovan girl’s fingerbone near the bottom but worked bone and ivory artefacts higher up, suggesting that the Denisovans could have made the kind of tools normally associated with modern humans.
‘However, direct dating work by the Oxford Radiocarbon Unit reported at the ESHE meeting suggests the Denisovan fossil is more than 50,000 years old, while the oldest ‘advanced’ artefacts are about 45,000 years old, a date which matches the appearance of modern humans elsewhere in Siberia.’
Did they breed with other species?
Yes. Today, around 5 per cent of the DNA of some Australasians – particularly people from Papua New Guinea – is Denisovans.
Now, researchers have found two distinct modern human genomes – one from Oceania and another from East Asia – both have distinct Denisovan ancestry.
The genomes are also completely different, suggesting there were at least two separate waves of prehistoric intermingling between 200,000 and 50,000 years ago.
Researchers already knew people living today on islands in the South Pacific have Denisovan ancestry.
But what they did not expect to find was individuals from East Asia carry a uniquely different type
Source: Daily Mail
