Two new studies suggest that it was interbreeding and absorption into larger populations and not some dead-end extinctions that caused Neanderthals and later hunter-gatherers to disappear.
1. A study reported in PLOS One suggests that some 40,000 years ago Neanderthals gradually disappeared as they interbred with and were absorbed by a much more numerous population of our ancestors.
Daily Mail: …. Neanderthals were not driven to extinction by their lack of brains, a new study suggests. Instead, it is more likely that they disappeared 40,000 years ago because of interbreeding and assimilation with our early modern human ancestors, scientists believe.
An analysis of archaeological evidence dating back 200,000 years strips away some of the myths surrounding Neanderthals and reveals they were more advanced and sophisticated than has widely been thought.
The differences between the two human sub-species are not enough on their own to account for the demise of the Neanderthals, say the two US and Dutch researchers.
Dr Paola Villa, from the University of Colorado Museum, and Professor Wil Roebroeks, from Leiden University, wrote in the online journal Public Library of Science ONE: ‘Genetic studies now suggest that the debate on the demise of the Neanderthals needs to be reframed in terms of some degree of interbreeding. ‘In that sense, Neanderthals did not go extinct, even though their distinctive morphology did disappear.
‘We conclude that all the “archaeology-based” explanations for the demise of the Neanderthals… are flawed.’
Neanderthals thrived in Eurasia for 300,000 years but vanished around 40,000 years ago as early modern humans began to settle in Europe. In the past, experts have theorised that Neanderthals died out because they were mentally, technologically and culturally inferior to the newcomers and unable to compete for limited resources. But more recent evidence has shown that Neanderthals made effective tools and weapons, wore ornaments such as eagle claws, used ochre and pitch, ate plants and fish as well as big game and created organised living spaces in their caves. In many cases this was happening before the arrival of modern humans, so the behaviours could not have been copied from them.
Reviewing the evidence, the scientists pointed out that 200,000 years ago Neanderthals were using fire to produce pitch from tree bark. Experiments showed that the process required high temperatures and an oxygen-free environment such as an enclosed pot, suggesting a high level of technical knowledge.
Neanderthal DNA, which was sequenced in 2010, shows clear evidence of interbreeding, the researchers add. Neanderthals and early modern humans are most likely to have interbred in Europe and the Middle East around 50,000 years ago.
Today Neanderthal inheritance is estimated to make up between 1% and 4% of the DNA of people outside Africa. Interbreeding could be one reason why Neanderthals vanished, according to the scientists. They were not so much driven to extinction as assimilated.
2. The second is a Scandinavian study published in Science and suggests that when farming communities expanded (10 to 20,000 years ago) they gradually absorbed the hunter gatherers.
Past Horizons: “Hunter-gatherers had much lower genetic diversity than farmers. This suggests that the foraging groups were in low numbers compared to farmers“, says Mattias Jakobsson.
Jan Storå at Stockholm University shares Mattias’ fascination. “The low variation in the hunter gatherers may be related to oscillating living conditions likely affecting the population sizes of hunter-gatherers. One of the additional exciting results is the association of the Mesolithic individual to both the roughly contemporaneous individual from Spain but also the association to the Neolithic hunter-gatherers.”
The study confirms that hunter-gatherers and farmers were genetically distinct and that migration spread farming practices across Europe, but the team was able to go even further by demonstrating that the Neolithic farmers had substantial admixture from hunter-gatherers. Surprisingly, the hunter-gatherers from the Baltic Sea displayed no evidence of introgression from farmers.
“We see clear evidence that people from hunter-gatherer groups were incorporated into farming groups as they expanded across Europe“, says Pontus Skoglund. “This might be clues towards something that happened also when agriculture spread in other parts of the world.”
“The asymmetric gene-flow shows that the farming groups assimilated hunter-gatherer groups, at least partly“, says Mattias Jakobsson. “When we compare Scandinavian to central European farming groups that lived at about the same time, we see greater levels of hunter-gatherer gene-flow into the Scandinavian farming groups.”
Skoglund et al. Genomic Diversity and Admixture differs for Stone-Age Scandinavian Foragers and Farmers. Science, 2014 DOI:10.1126/science.1253448
Abstract: Prehistoric population structure associated with the transition to an agricultural lifestyle in Europe remains contentious. Population-genomic data from eleven Scandinavian Stone-Age human remains suggest that hunter-gatherers had lower genetic diversity than farmers. Despite their close geographical proximity, the genetic differentiation between the two Stone-Age groups was greater than that observed among extant European populations. Additionally, the Scandinavian Neolithic farmers exhibited a greater degree of hunter-gatherer-related admixture than that of the Tyrolean Iceman, who also originated from a farming context. In contrast, Scandinavian hunter-gatherers displayed no significant evidence of introgression from farmers. Our findings suggest that Stone-Age foraging groups were historically in low numbers, likely due to oscillating living conditions or restricted carrying-capacity, and that they were partially incorporated into expanding farming groups.