Neanderthals and humans had ample time for interbreeding
20 August 2014
Researchers have accurately dated Neanderthal extinction across Europe, showing there was considerable overlap with early modern humans arriving from Africa.
Neanderthals coexisted with early modern humans in Europe for several thousand years, a six-year study has revealed.
By dating 196 samples of bone, charcoal and shell across 40 key European sites from Russia to Spain, researchers have found that Neanderthals were extinct by 39,000 years ago.
The first Homo sapiens, the early modern humans, arrived in Europe from western Asia, and ultimately Africa, around 45,000 years ago. The two populations coexisted in Europe for several thousand years, allowing plenty of time for contact between them.
By dating samples from transitional sites, which contain tools either from the first early modern humans in Europe or the last Neanderthals, researchers found that the two groups overlapped for between 2,600 and 5,400 years.
A gradual extinction
Neanderthals did not all become extinct at the same time, the study shows. Their disappearance was staggered, suggesting that they were replaced by early modern humans as a result of local population extinctions, rather than being quickly overrun.
The research, published today in the journal Nature, was led by Prof Thomas Higham from Oxford University and included work by Museum archaeologist Dr Roger Jacobi, who is sadly now deceased.
Rather than early modern humans rapidly replacing Neanderthals, Prof Higham said that the study ‘supports a more complex picture, one characterised by a biological and cultural mosaic that lasted for several thousand years’.
Twenty thousand years of interactions
While no archaeological evidence has been found to show that the Neanderthals and early modern human groups lived closely together, modern human DNA proves that interbreeding took place. Modern people descended from the early humans who arrived from Africa carry about 2% Neanderthal DNA in their genomes today.
Museum human origins expert Prof Chris Stringer said that we don’t yet know how often or precisely where Neanderthals and early modern Europeans interbred. But we do know that Neanderthals in Asia probably interbred with early modern humans somewhere between 50-60,000 years ago, much earlier than the time of their overlap in Europe.
This means that the two populations potentially interacted for up to 20,000 years, starting in Asia about 60,000 years ago and ending about 39,000 years ago in Europe when the last Neanderthals went physically extinct.
Some Neanderthal sites show evidence of more advanced technology and behaviour in the last few thousand years before they went extinct, suggesting that acculturation, or cultural transmission of tools and behaviour between the two groups, took place.
The last Neanderthals
The study used techniques that purified the samples for carbon dating, removing any influence of modern carbon material that could make dates appear younger. Several sites in Spain, for example, that were previously thought to be some of the last outposts of late-surviving Neanderthals, were dated as much older in this study.
Some known Neanderthal sites, such as those in Siberia, have still not been accurately dated, so there is a possibility of some late-surviving populations being identified there.
'But the overall pattern seems clear,' said Prof Stringer. 'The Neanderthals had largely, and perhaps entirely, vanished from their known range by 39,000 years ago.'
What wiped out the Neanderthals?
Around the time of the Neanderthals' extinction, an episode of natural climate change caused cold and dry conditions across Europe.
'It remains to be seen whether that event delivered the final straw to a Neanderthal population that was already low in numbers and genetic diversity, and trying to cope with economic competition from incoming groups of Homo sapiens,' said Prof Stringer.
- by Hayley Dunning