Masters of Science: the new human story
The Natural History Museum's Chris Stringer on recent discoveries that are challenging the way we think about our ancestors.
Produced, filmed and edited by James Sandy; animation by Russell Birkett; design by Mark Leeds and Kevin Wilson
Transcript
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I've been researching on human evolution for about 50 years. And even ten or 15 years ago, we had the view that human evolution in the last 500,000 years was a relatively simple process, that we had a gradual change of species through time. A species called Homo heidelbergensis gradually evolved to the Neanderthals in Europe and Asia, and it evolved to Homo sapiens in Africa. We now know this story is a lot more complicated than that.
So here, we've got two Neanderthal fossils from Gibraltar. And the one on the left, from Forbes Quarry, was the first Neanderthal I ever looked at and studied. And at that time, the Neanderthals were actually regarded as the direct ancestors of modern humans, and if we had a fossil sequence in Europe, we would see the Neanderthals gradually evolving into modern people. We now know, in fact, that the Neanderthals and us are two separate lineages from a common ancestor, which generally has been regarded as the species Homo heidelbergensis.
And then, maybe 35,000 years ago, it was thought that these two species came together in Europe, and very quickly, the Neanderthals were completely replaced by the modern humans. We now know from DNA evidence, including even on some of these Gibraltar Neanderthal fossils, that actually the story is more complicated than that.
By the year 2010, scientists were able to reconstruct whole Neanderthal genomes. And once those were examined and compared with our own, there was a big surprise. It turned out that most of us alive today have an input of about two per cent Neanderthal DNA in our genomes. And that means our ancestors must have mixed with Neanderthals, interbred with them, maybe 50,000 or 60,000 years ago. So this idea that Neanderthals were completely replaced by modern humans has been falsified by new science.
And even more remarkably, both DNA and fossils are contributing to a re-evaluation of the last 500,000 years or so of our evolution. So in particular, this species, Homo heidelbergensis, which has been regarded as the common ancestor of us and the Neanderthals, possibly is too recent in time. DNA evidence suggests the common ancestor may have lived further back. And not only that, studying the fossils themselves suggests that this species, Homo antecessor, might actually have a face that's more like the common ancestor of us and the Neanderthals. And thus, the place of heidelbergensis is in doubt.
What we can look forward to in the next ten or 20 years is both DNA evidence and new fossil evidence fleshing out many of these empty areas of that tree, and helping to unravel the full story of our ancestry.
