Newly published results from an international team of researchers show that most of an earlier population of Neanderthals in Europe had already died off around 50,000 years ago.
Previously, the established view was of a stable Neanderthal population in Europe from nearly 250,000 to 30,000 years ago and then they disappeared from the archaeological record after modern humans arrived, however this new research suggests the accepted paradigm must be revised.
A new perspective
This new perspective on the Neanderthals comes from a study of ancient DNA published today in Molecular Biology and Evolution. The results indicate that most European Neanderthals had died off as early as 50,000 years ago. After which, a smaller group of Neanderthals recolonised central and western Europe, where they survived until 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 recovered, and that all this took place long before they came into contact with modern humans came as a complete surprise to them. 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”, says Love Dalén, associate professor at the Swedish Museum of Natural History in Stockholm.
Teeth from a Neandertal boy, northern Spain. Photo: Centro de Evolución y Comportamiento Humanos (UCM-ISCIII)
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.
Older European Neanderthal fossils, as well as fossils from Asia, had much greater genetic variation
“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”, says Anders Götherström, associate professor at Uppsala University.
New methods of DNA sequencing
It must be stressed however that the results presented in the study were based entirely on severely degraded DNA obtained from mtDNA sequences in 13 Neanderthal individuals, and the analysis required advanced laboratory and computational methods to create statistically viable results. Using control region sequences the use of the statistical Bayesian demographic simulation provided a strong case for population fragmentation and decrease around 48,000 years ago (represented by a lack of genetic diversity due to a shrinking gene pool) followed by separate movement of external subpopulations (of Neanderthals) that would not be present if this was a single stable population. An explanation for these results is that of population turnover in Western Europe during early Marine Isotope Stage 3, (c. 60kya) predating the arrival of anatomically modern humans in the region.
The research team involved experts from a number of countries, including statisticians, experts on modern DNA sequencing and palaeoanthropologists 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 possibly 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”, says Juan Luis Arsuaga, professor of human palaeontology at the Universidad Complutense of Madrid.
Source: Uppsala Universitet
More information:
- Love Dalén et al., 2012 , Partial genetic turnover in neandertals: continuity in the east and population replacement in the west
Mol Biol Evol doi: 10.1093/molbev/mss074 : First published online: February 23, 2012 - Dr Love Dalén Swedish Museum of Natural History
- Centro de Evolución y Comportamiento Humanos
- Molecular Biology and Evolution
for other views:
- Banks, W. et al., 2008. Neanderthal extinction by competitive exclusion. PloS ONE 3, e3972, 1-8.
- Fabre V, Condemi S, Degioanni A (2009) Genetic Evidence of Geographical Groups among Neanderthals. PLoS ONE 4(4): e5151. doi:10.1371/journal.pone.0005151
- Sørensen, B. 2011. Demography and the extinction of the European Neanderthals. Journal of Anthropological Archaeology 30 (2011) 17-29:
- Wenzel, S. 2007. Neanderthal presence and behaviour in Central and Northwestern Europe during MIS 5e, in The climate of past interglacials. F. Sirocko, M. Claussen, M. Goñi, T. Litt, Eds. 173-193. Elsevier, Amsterdam.