‘Super-archaic’ human mated with the primitive ancestor of both Denisovans and Neanderthals 700,000 years ago
- Researchers used special software to compare the DNA of ancient human fossils
- They also found that Denisovans and Neanderthals split 600,000 years ago
- This is a much older estimate of the species’ divergence than proposed before
A ‘super-archaic’ human mated with the primitive ancestor of both Denisovans and Neanderthals 700,000 years ago, researchers have concluded.
This was the earliest known episode of interbreeding between different populations of ancient humans — and involved the most distantly related species.
The ‘super-archaic’ humans split from all other humans in the evolutionary tree some two million years ago.
Experts had used special software to examine human evolutionary history based on genetic evidence recovered from fossils found in Spain‘s Sima de los Huesos cave.
The algorithm also concluded that Denisovans and Neanderthals were already distinct species 600,000 years ago — much earlier than previously thought.
A model developed by the same researchers in 2017, in contrast, had proposed that the two species split around 381,000 years ago.
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A ‘super-archaic’ human mated with the primitive ancestor of both Denisovans and Neanderthals 700,000 years ago, researchers have concluded. Pictured, the researcher’s model of the history of human evolution. The coloured lines between the branches represent episodes of interbreeding and the transfer of genes between the various human species
The team’s new model supports the view that modern humans and their ancestors dispersed out from Africa into Eurasia only three times.
These migrations are thought to have happened around 1.9 million years ago with the super-archaics, 700,000 years ago for the Neanderthal–Denisovan ancestors and 50,000 years ago for modern humans.
Large-brained hominins first appeared in Europe and Asia about 600,000 years ago, in the period known as the middle Pleistocene — which was an important milestone for early humans.
To shed light on this period in human evolution, anthropologist Alan Rogers of the University of Utah and colleagues considered eight models with various genetic combinations that may have resulted from interbreeding between early hominins.
They also included data from Neanderthals from the Altai Mountains of Siberia and the Vindija Cave in Croatia, as well as from modern Europeans.
‘We’ve never known about this episode of interbreeding and we’ve never been able to estimate the size of the super-archaic population,’ said Professor Rogers.
‘We’re just shedding light on an interval on human evolutionary history that was previously completely dark.’
‘These findings about the timing at which interbreeding happened in the human lineage is telling something about how long it takes for reproductive isolation to evolve,’ he added.
The algorithm also concluded that Denisovans (pictured) and Neanderthals were already distinct species 600,000 years ago — much earlier than previously thought
‘Our [statistical] software ignores the within-population component of genetic variation. For this reason, it is unaffected by recent changes in population size, which often interfere with efforts to study deep history,’ Professor Rogers added.
‘In effect, we have cleared away some of the brush that often obscures the view of the distant past.’
The full findings of the study were published in the journal Science Advances.
Experts had used special software to examine human evolutionary history based on genetic evidence recovered from fossils found in Spain’s Sima de los Huesos cave
WHO WERE THE DENISOVANS?
The Denisovans are an extinct species of human that appear to have lived in Siberia and even down as far as southeast Asia.
Although remains of these mysterious early humans have only been discovered at one site – the Denisova Cave in the Altai Mountains in Siberia, DNA analysis has shown they were widespread.
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.
DNA analysis of a fragment of pinky finger bone in 2010, (pictured) which belonged to a young girl, revealed the Denisovans were a species related to, but different from, Neanderthals.
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.
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.
DNA analysis of a fragment of a fifth digit finger bone in 2010, which belonged to a young girl, revealed they were a species related to, but different from, Neanderthals.
Later genetic studies suggested that the ancient human species split away from the Neanderthals sometime between 470,000 and 190,000 years ago.
Anthropologists have since puzzled over whether the cave had been a temporary shelter for a group of these Denisovans or it had formed a more permanent settlement.
DNA from molar teeth belonging to two other individuals, one adult male and one young female, showed they died in the cave at least 65,000 years earlier.
Other tests have suggested the tooth of the young female could be as old as 170,000 years.
A third molar is thought to have belonged to an adult male who died around 7,500 years before the girl whose pinky was discovered.