Nature has a new paper, Placing late Neanderthals in a climatic context:
…This study shows that the three sets translate to different scenarios on the role of climate in Neanderthal extinction. The first two correspond to intervals of general climatic instability between stadials and interstadials that characterized most of the Middle Pleniglacial and are not coeval with Heinrich Events. In contrast, if accepted, the youngest date indicates that late Neanderthals may have persisted up to the onset of a major environmental shift, which included an expansion in global ice volume and an increased latitudinal temperature gradient….
The report in Nature News really unpacks the thrust of this paper:
The researchers report in Nature, that of the three main radiocarbon dates given as possible extinction times for the Neanderthals — 32,000 years, 28,000 years and 24,000 years — only the most recent seems to have occurred at the same time as a climate shift. This most recent date is also the most controversial, meaning that it is generally more likely that it was competition with modern humans, rather than the bitter cold, that did for the Neanderthals.
“The take-home message is that we can eliminate catastrophic climate change as a factor for Neanderthal extinction,” Tzedakis says.
What to think? I don’t know much about stratigraphy and radiometric dating, but, I think context is important. The research on ground sloths in the West Indies strongly suggests that the necessary condition for megafaunal extinction within the last 100,000 years has been the arrival of modern humans. This does not mean it is a sufficient condition, rather, it seems likely that humans force extinctions at the margins. Populations naturally go through cycles dictated by exogenous factors; e.g., climate and disease. It is on the downswings that human predation can send the population over the edge and toward extinction.
In terms of Neandertals, we need to view our cousins as another megafaunal population. They persisted across their extant range for hundreds of thousands of years, shifting north and south with the waxing and waning of the Ice Ages. If climate fluctuations can be thought of as independent trials it stands to reason that many species will naturally experience a sharp enough population crash during one transition that will result in extinction, given enough trials. But, the conditional probabilities of this are altered by the coincidental arrival of modern human beings. And these probabilities need to be modified further by the prior knowledge that modern human arrival seemed to have mysteriously coincided with megafaunal extinctions elsewhere (e.g., Australia and the New World, and also in Madagascar and New Zealand).
Comments are closed.