20 Aug 2014

How long did neanderthals rub shoulders with our ancestors?

Did our ancestors, early modern humans, live alongside neanderthals? Did we drive them extinct through pre-historic ethnic cleansing? Or was it “Ug!” at first sight and we tenderly inter-bred with them until their species disappeared?

The rise of homo sapiens and the demise of homo neanderthalensis is shrouded in mystery. But today a little of that mist is lifted by a very thorough job of carbon dating early human remains from across Europe.

A report in tomorrow’s journal Nature looked at 40 different early human sites across Europe and concludes that neanderthals were already starting to disappear from Europe by the time early modern humans made their way up from north Africa.

But instead of neanderthals then dying out completely, the analysis shows they rubbed shoulders with our ancestors for at least 2,500 years and possibly as long as 5,000.

The new timeline is a great help for paleoanthropologists, who were happy to admit the previous picture was a total mess.

It helps clear up a major dispute about how long neanderthals hung around. Some scientists thought an isolated population was clinging on in Gibraltar 30,000 years ago. The new date for their extinction is 39,000 years.

But importantly it shows there was a definite period of overlap. That fills in an important blank. Some researchers have long argued neanderthals borrowed from early modern human culture towards the end of their time. Indeed later neanderthal tools are much more like those made by early modern human interlopers suggesting cultural exchange.

And if that was happening, was there breeding? Neanderthals and humans definitely got together. Around 2 per cent of our genome is “neanderthal” DNA. But the latest evidence is that this happened much earlier in our history when we were coming out of Africa and ran into neanderthals in Asia around 90,000 years ago.

There still could have been close contact between our ancestors and neanderthals towards their end in Europe and the evidence of cultural exchange supports that. But it may have been uncommon.

Based on genetic studies, neanderthals were getting few in number by 45,000 years ago. They may have been living in small groups isolated from each other. Similar to the last uncontacted tribes in today’s Amazon.

That fact helps explain why they may have died out completely. A period of rapid climate change 39-40,000 years ago is thought to have challenged both early modern humans and neanderthals.

While our ancestors were present in larger numbers, possibly with cultural adaptations that allowed us to survive, we may have hung on, as the neanderthals shuffled off.

Alternatively, if, challenged by the climate, we ended up competing for resources, more numerous homo sapiens could have starved or killed the neanderthals out. Perhaps one of the first of many extinctions notched up by modern man.

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