London: Far from wiping out Neanderthals overnight, modern humans rubbed along with their shorter and stockier cousins for thousands of years, giving plenty of time for the two groups to share ideas — and have sex.
The most accurate timeline yet for the demise of our closest relatives, published on Wednesday, shows Neanderthals overlapped with present-day humans in Europe for between 2,600 and 5,400 years before disappearing about 40,000 years ago.
Pinpointing how and when the Neanderthals became extinct has been tough because the mainstay process of radiocarbon dating is unreliable for samples that are more than 30,000 years old, due to contamination.
The latest six-year project by researchers at the University of Oxford used modern methods to remove contaminants and accurately date nearly 200 samples of bone, charcoal and shell from 40 important archaeological sites across Europe.
The data showed that Neanderthals vanished from Europe between 39,000 and 41,000 years ago — but rather than being replaced rapidly by modern humans, their disappearance occurred at different times across sites from the Black Sea to the Atlantic.
“Now that we are using better techniques, the picture is becoming much more clear in terms of the process by which Neanderthals disappeared from Europe,” said lead researcher Tom Higham. “Our results suggest there was a mosaic of populations.” Scientists already know from DNA evidence that there was some interbreeding between the two groups, although it is not clear whether this occurred once or many times. Recent studies have suggested between 1.5 and 2.1 per cent of the DNA of modern non-African human populations originates from Neanderthals.
“In a way, our close cousins, as Neanderthals are, aren’t extinct,” according to Higham. “They carry on in us today.” Palaeoanthropologist Chris Stringer of the Natural History Museum in London, who was not involved in the research, said the new findings were “striking” and backed up the idea that modern humans and Neanderthals may have learnt from each other.
He believes interbreeding probably first occurred in Asia soon after modern humans began to leave Africa around 60,000 years ago, so the latest evidence indicates the two populations may have been in some kind of contact for up to 20,000 years — much longer than in Europe alone.
Belgium holds the secret to producing some of the finest chocolate, waffles and beer in the world but it turns out the country may also have the answer to where the last Neanderthals died out.
Scientists have analysed 196 samples of bone, charcoal and shell from 40 key Neanderthal sites from Spain to Russia and concluded that this species of thickset humans who adapted to cold climates disappeared throughout this entire region before 39,000 years ago.
This means that the overlap in Europe with the newly arrived Homo sapiens, with their more gracile anatomy and more complex stone and bone tools, must have lasted at least 4,000 years.
It could have been as long as 20,000 years in Asia, which anatomically modern humans had colonised long before reaching Europe.
Previous studies have suggested that Neanderthals, which first emerged in Eurasia about 250,000 years ago, quickly died out when H. sapiens appeared, suggesting intense competition for resources and even violent conflict, culminating in a “last-stand” in southern Spain.
However, more recent studies have found that there was a degree of genetic mixing and interbreeding between the two strands of humanity, especially in Asia, although this did not extend to a compete assimilation of the two.
The latest study produced the first accurate dates for the final decline of the Neanderthals with the help of sophisticated developments in radiocarbon dating. It found a clear overlap within Europe that spanned some 25 to 250 generations — between 470 and 4,900 years depending on the region.
The overlap also fits with archaeological data on the kind of tools that each used, suggesting a period when Neanderthals began to copy the more sophisticated toolmaking of the new migrants.
“We believe we now have the first robust timeline that sheds new light on some of the key questions around the possible interactions between Neanderthals and modern humans,” said Professor Higham.
“The chronology also pinpoints the timing of the Neanderthals’ disappearance, and suggests they may have survived in dwindling populations in pockets of Europe before they became extinct,” Professor Higham said.
A cave system near Spy in Belgium, rather than caves in Spain, may be one of the last sites in Europe for Neanderthals to have lived, although it is still too early to say this for sure, he said.
However, Professor Chris Stringer, head of human origins at the Natural History Museum in London, said that the new analysis did not extend to eastern Neanderthal sites in Uzbekistan and Siberia — meaning it is possible that the species still survived in these enclaves for longer than in Europe.
“But the overall pattern seems clear. The Neanderthals had largely, and perhaps entirely, vanished from their known range by 39,000 years ago,” Professor Stringer said.
The demise coincided with a change in the climate to colder, drier conditions, he added. “It remains to be seen whether that event delivered the coup de grace to a Neanderthal population that was already low in numbers and genetic diversity, and trying to cope with the economic competition from incoming groups of homo sapiens,” he said.
Many scientists now reject the notion that Neanderthals were dim-witted brutes and point to evidence of use of symbolic objects, which may have been learnt from modern humans.
The Oxford team dated a number of items from sites of so-called transitional stone tool industries — viewed as either the work of the last of the Neanderthals or early modern humans — and found they were all between 40,000 and 45,000 years old, indicating a period of possible cultural exchange.
Interestingly, they found no evidence that Neanderthals and modern humans lived particularly closely together. Rather, Neanderthals probably survived in dwindling populations in pockets of Europe before dying out altogether.
It is unclear what killed off the Neanderthals, although theories include an inability to adapt to climate change and increased economic competition from more agile modern humans.
While the latest work provides the most robust timeline so far of the last days of the Neanderthals, there are still gaps in coverage, particularly in Siberia and eastern regions of Eurasia. That is something the researchers plan to address in follow-up investigations.
“Ultimately, our aim is to create kind of movies that show the arrival and departure of different subspecies of humans across Europe,” Higham said in an interview filmed in his lab.
“We are part-way towards that but there is a still a lot more work we can do.” Some scientists have hypothesised that late-surviving groups of Neanderthals lived in places such as Gibraltar after 40,000 years ago, but the latest dating provides no evidence of this, according to the Oxford team, whose findings were published in the journal Nature.
