Research shows that climate change was more likely to blame for the extinction of Neanderthals than modern humans, writes Dick Ahlstrom.
A nasty turn in the weather likely served to wipe out the Neanderthals, a form of early humans that coexisted in Europe with our modern human descendants. While the Neanderthals were unable to cope with the advance of ice and glaciers, our ancient cousins had the brainpower to survive.
Climate change has played a significant role in human evolution and now research by an international team of scientists suggests it could have conspired with modern humans present at the time to drive the Neanderthals out of existence. Their study, published this morning in Nature magazine, was also presented yesterday at the British Association for the Advancement of Science festival.
One longstanding view of the demise of the Neanderthal is that smarter, more adaptable modern humans basically hunted them out of existence as a way to knock out either a perceived threat or competitor for food resources.
The new study however puts a different complexion on it, suggesting that unstable climate and a final onset of extremely cold weather actually drove the Neanderthals over the edge during the last ice age.
The research group from Greece, the US, Spain, the UK and Germany used fossil remains from one of the last Neanderthal strongholds in Europe in southern Spain, Gorham's Cave. Material there, assessed using radio-carbon dating, suggests the Neanderthals lasted at least until 30,000 to 32,000 years ago. The authors also cite newer research that could bring the Neanderthals up to about 28,000 years ago and possibly as recent as 24,000 years ago, although this date remains contentious amongst the scientific community.
The challenge was to make the connection between known climatic events and reliable dating of archeological material left behind by the Neanderthals. Lead author Dr Polychronis Tzedakis of the University of Leeds and the University of the Aegean in Greece described how his team took an "alternative approach" in overcoming the difficulties.
Fossil remains are typically given an approximate age using radio-carbon dating through the measurement of radioactive carbon 14 in a sample. Levels of this gas vary over time, however, making very accurate dating problematic.
THE TEAM DIDN'T try to devise a calendar for the extinction but simply mapped carbon 14 dates of interest associated with the Neanderthals directly onto a carbon 14 series from a deep-sea sediment core taken from the Cariaco Basin in Venezuela.
This core gives an accurate view of past climate but its carbon 14 dating has also been identified.
The researchers linked in the dated remains from 32,000, 28,000 and 24,000 years ago, looking for an indication of what the palaeoclimate was like at these three periods.
They found that the older two dates were associated with a high level of climate instability with short term swings between cold and warm.
However, these changes were not severe enough in themselves to have caused Neanderthal extinction, the authors suggest.
"By comparison, and taken at face value, the youngest and more contentious date suggests that Neanderthals at Gorham's Cave may have persisted up to the onset of a major environmental shift, which included an expansion in global ice volume," and increasingly cold weather that gradually reached further and further south, the authors write.
"This would imply a greater role of climate in Neanderthal extinction, not necessarily directly but perhaps in the form of climate-driven intensified competition as a result of increased southward human migration from higher latitudes," they conclude.
So, while our ancestors may have driven Neanderthals from this world, the ultimate cause was the onset of the last glacial maximum, when Ireland was under the ice along with most of northern Europe and sea levels plummeted by 20m to 30m. Perhaps if the weather had been a bit kinder we might have Neanderthals living next door today?