Human evolution researchers agree: Neandertals are now extinct. Yet when it comes to when and why our hominid cousins disappeared, the consensus ends. That former mystery may be closer to being solved thanks to radiocarbon dating of Neandertal hearths in a Gibraltar cave at the southern tip of Spain. The findings suggest that some Neandertals survived thousands of years longer than previously thought, taking refuge in corners of southern Europe where the climate and environment were favorable and where modern humans were still thin on the ground.
An international team has been excavating the Gibraltar cave--known as Gorham's Cave--for the past 7 years. Although no hominid fossils have been found yet, the excavators have uncovered numerous stone tools belonging to a culture known as the Mousterian, which is characteristic of Neandertals. The team, led by biologist Clive Finlayson of the Gibraltar Museum, obtained 22 radiocarbon dates from small pieces of charcoal in hearths associated with Mousterian tools. The dates range from 23,000 to 33,000 years ago with a cluster at about 28,000 raw "radiocarbon years," the team reports online today in Nature. (Although raw radiocarbon dates must be calibrated to obtain true calendar years, which during this time period are probably several thousand years older, the precise calibration of such ancient dates is still uncertain. Thus the team has followed routine practice and reported only uncalibrated dates.)
The Gibraltar dates appear to represent the latest known Neandertal sighting, because there are no other accepted sites younger than 30,000 uncalibrated years ago. But the Gibraltar Neandertals were not entirely alone: Although there are very few modern human sites in southern Spain or Portugal at that time, one site about 100 kilometers east at Bajondillo, Spain, has been dated to about 32,000 uncalibrated years ago. The team concludes that Neandertals did not rapidly disappear from the area as moderns advanced across Europe but co-existed with them by taking refuge at Gibraltar and other southern sites over thousands of years. "While pioneer modern humans were staking tenuous footholds" in the region, the last Neandertals "were hanging on," Finlayson says. He points out that Gibraltar was surrounded by coastal wetlands and woodlands and blessed with mild temperatures around this time, making the peninsula an excellent refuge from competition with the moderns.
Anthropologist Eric Delson of the City University of New York says that "the dates appear fully supported" and adds that the notion of Neandertal refugia is "quite reasonable." But some archaeologists question the late dates. "I have considerable reservations," says archaeologist Paul Mellars of the University of Cambridge in the United Kingdom. Mellars argues that many of the new dates actually cluster around 30,000 to 31,500 uncalibrated years ago, and the later ones could be the result of contamination of the charcoal samples.
For more on Neandertals and radiocarbon dating, stay tuned for the 15 September issue of Science.