Questions remain unresolved as to whether the Neanderthals died out because of competition with modern people or because of deteriorating climatic conditions. Although scientists have gained increased knowledge of past climate it has been difficult to pinpoint the climatic character at the time of the Neanderthal disappearance. A new study by an international team of researchers, published this week in the prestigious journal Nature, has developed a breakthrough approach to address this issue (Nature, September 13, 2007).
"Our findings suggest that there was no single climatic event that caused the extinction of the Neanderthals" says palaeoanthro-pologist Katerina Harvati. Only a controversial date for very late Neanderthal survival places their disappearance just before a major environmental shift. "Even in this case" continues Harvati "the role of climate would have been indirect, perhaps promoting competition with other human groups".
"There are three main limitations to understanding the role of climate in the Neanderthal extinction" explains palaeoecologist Chronis Tzedakis: uncertainty over the exact timing of the Neanderthal disappearance; uncertainties in converting radiocarbon dates to actual calendar years; and the chronological imprecision of the ancient climate record. "Our novel method circumvents the last two problems" adds palaeoclimatologist Konrad Hughen. "We were therefore able to provide a much more accurate picture of the climatic background at the time of the Neanderthal disappearance". "More generally," continues Hughen "our approach offers the huge potential to unravel the role of climate in critical events of the recent fossil record as it can be applied to any radiocarbon date from any deposit".
The new method was applied by the researchers to three possible dates for the Neanderthal extinction obtained from Gorham's cave, Gibraltar - a site thought to have been occupied by some of the latest surviving Neanderthals. The first two of these dates (~32 and ~28 thousand radiocarbon years ago) relate to conditions that are not distinct from the general climatic instability of the last glacial period. The much more controversial date of ~24 thousand radiocarbon years ago places the last Neanderthals just before a major environmental shift, with an expansion of ice sheets and onset of cold conditions in northern Europe. Gibraltar's climate, however, remained relatively unaffected "perhaps as a result of warm water from the subtropical Atlantic entering the western Mediterranean" according to palaeoceanographer Isabel Cacho.
The study was conducted by Chronis Tzedakis (University of Leeds); Konrad Hughen (Woods Hole Oceanographic Institution); Isabel Cacho (University of Barcelona); Katerina Harvati (Max Planck Institute for Evolutionary Anthropology).
P. C. Tzedakis, K. A. Hughen, I. Cacho & K. Harvati
Placing late Neanderthals in a climatic context.
Nature, Volume 448 Number 7159. September 13, 2007.