Scientists find clue to Neanderthal extinction
Washington: An international team of researchers, studying ancient DNA, have suggested that most Neanderthals in Europe already were largely extinct 50,000 years ago - long before modern humans first arrived in the continent.
The findings contradict the long-held notion that Neanderthal populations were stable in Europe for hundreds of thousands of years until modern Homo sapiens arrived.
The scientists say the Neanderthal human species already had died off as early as 50,000 years ago, but a small group recovered and survived for another 10,000 years in areas of central and western Europe before modern humans entered the picture.
The study is the result of an international project led by Swedish and Spanish researchers in Uppsala, Stockholm and Madrid.
“The fact that Neanderthals in Europe were nearly extinct, but then recovered, and that all this took place long before they came into contact with modern humans came as a complete surprise to us. This indicates that the Neanderthals may have been more sensitive to the dramatic climate changes that took place in the last Ice Age than was previously thought,” said Love Dalen, associate professor at the Swedish Museum of Natural History in Stockholm.
In connection with work on DNA from Neanderthal fossils in northern Spain, the researchers noted that the genetic variation among European Neanderthals was extremely limited during the last ten thousand years before the Neanderthals disappeared.
Older European Neanderthal fossils, as well as fossils from Asia, had much greater genetic variation, on par with the amount of variation that might be expected from a species that had been abundant in an area for a long period of time.
“The amount of genetic variation in geologically older Neanderthals as well as in Asian Neanderthals was just as great as in modern humans as a species, whereas the variation among later European Neanderthals was not even as high as that of modern humans in Iceland,” explained Anders Gotherstrom, associate professor at Uppsala University.
The results presented in the study are based entirely on severely degraded DNA, and the analyses have therefore required both advanced laboratory and computational methods.
The research team has involved experts from a number of countries, including statisticians, experts on modern DNA sequencing and paleoanthropologists from Denmark, Spain and the US.
Only when all members of the international research team had reviewed the findings could they feel certain that the available genetic data actually reveals an important and previously unknown part of Neanderthal history.
“This type of interdisciplinary study is extremely valuable in advancing research about our evolutionary history. DNA from prehistoric people has led to a number of unexpected findings in recent years, and it will be really exciting to see what further discoveries are made in the coming years,” stated Juan Luis Arsuaga, professor of human paleontology at the Universidad Complutense of Madrid.
The study results appeared in Molecular Biology and Evolution.