His team was in for a big surprise. The DNA analysis revealed an entirely new group of archaic humans, now dubbed the Denisovans , which split from a common ancestor with Neanderthals some , years ago. Once again, comparisons with modern human genomes showed that the two interbred.
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Genetic studies reveal this to have happened in Eurasia. They also show that Denisovans ranged from Siberia to South-East Asia, and that at least one of their genes helps modern Tibetans to live at high altitude. The idea that our ancestors hybridised with other hominins was once dismissed. Now it was starting to look as though they would mate with anything vaguely human.
Denisovans are nearly ghosts: we have that one finger bone and a few molars as a physical testament to their existence, but no more. Then in , a true ghost emerged from the genomes of 44 individuals who lived in the Middle East between 14, and years ago. Their DNA held genetic markers indicative of a distinct group of ancient H. The members of this population are now known as Basal Eurasians , and they present a conundrum.
Their DNA, which is still found in modern Europeans, shows none of the telltale signs of interbreeding with Neanderthals.
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This came as a surprise because ancestral humans mated with Neanderthals very soon after leaving Africa 60, years ago in the migration that was to give rise to all people of non-African heritage alive today. The most-likely explanation is that soon after that migration, a group of humans became isolated while the rest bumped into and mated with Neanderthals. Because there are no known fossils belonging to Basal Eurasians, it is impossible — for now — to say why they were isolated.
Perhaps it was just down to where they settled, far from other groups. Or maybe they developed cultural differences. The Basal Eurasian research showed that rich insights into human history can be gleaned from DNA alone. But, like the Neanderthal and Denisovan studies, it relied on obtaining DNA from fossils, something that remains a huge challenge. DNA degrades with time, so it takes special fossils and special skills to extract it from very old bones, particularly ones that have spent thousands of years buried in hot climates. However, in the mids, geneticists were already discussing another approach.
Among others, Jeffrey Wall, now at the University of California, Los Angeles, and Vincent Plagnol, now at University College London, suggested that it might be possible to spot signs of extinct populations in the DNA of modern humans, simply by using clever statistics. The broad idea is that all DNA is subject to random mutations that accumulate over millennia and are passed down from generation to generation. These are presumed to come from populations that evolved separately from our own species for thousands of years before mating with humans.
Statistical modelling can then produce estimates of when the two groups mated and how different the other population was from our ancestors. The past few years have seen several attempts to refine these methods and apply them to Africa — the birthplace of our species and the setting for a slice of our history that we know very little about. This new research has revealed the presence of at least one ancient ghost on the continent.
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Josh Akey at the University of Washington in Seattle, Sarah Tishkoff at the University of Pennsylvania and others have spent years sequencing and analysing the genomes of modern Africans who belong to groups with deep ancestral roots, including the Baka hunter-gatherers from Cameroon, and the Hadza and Sandawe from Tanzania. Jennifer T. Eric H. Terry Kleeman. Jennifer Tolbert Roberts. Amanda H.
Ronald Mellor. Peter Robertshaw. Terry F. Jill Rubalcala. Jonathan Mark Kenoyer. William Fash. William L. In the decades since its discovery, though, H. Its tool-making skills are seen as less significant too, because it is now clear that australopiths also produced stone tools.
The World in Ancient Times
One population of H. Discovered: , officially named the following year.
Probably evolved in Africa about 2 million years ago, quickly expanded and spread across Eurasia. The date of its extinction is debated — recent estimates suggest it may have disappeared by , years ago. Significance: It might be less well known than other extinct humans like the Neanderthals, but Homo erectus was an immensely important species. Unlike H. It used its long legs to stride out of Africa and spread across Eurasia , making it the earliest human species known to have migrated long distances.
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It was probably also the earliest human to learn how to control fire. It may have been the first to cook food too — an innovation some people think may have helped H.
Discovered: , not officially named until Appeared in Eurasia roughly , years ago and went extinct there about 40, years ago. Significance: Neanderthals are the most famous of all extinct human species, probably a consequence of the fact they were the first ancient human species to be discovered by scientists, almost years ago — several decades before Darwin put forward his theory of evolution by natural selection.
Neanderthals are also the best known of extinct human species: researchers have now found bones from hundreds of Neanderthals in countries across Europe , the western Asia and central Asia. Exactly when the line leading to H. Some recent research suggests the split happened more than a million years ago , with a Eurasian branch eventually evolving into the Neanderthals and the Denisovans while an African branch evolved into H.
Neanderthals made sophisticated stone and bone tools. Researchers have known for years that the Neanderthals could control fire, perhaps taking advantage of fires triggered by lightning. Recent evidence suggests that they may also have used knowledge of the chemical properties of minerals in their environment to start their own fires. Neanderthals also self-medicated and made art. Such findings suggest that the Neanderthals were more cognitively advanced than popularly believed.
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