New evidence shows that Neanderthals survived in refuges for much longer than originally thought, writes Dick Ahlstrom.
Archaeologists excavating an ancient cave in Gibraltar may have discovered the last known European refuge for the Neanderthals. Competition from rapidly spreading populations of modern humans coupled with a worsening climate wiped out this early human-like species, but much later than assumed given the new findings.
Neanderthals perfectly match the popular assumption of what Stone Age cavemen might have looked like. They inhabited western Eurasia from a time in the Middle Pleistocene between 500,000 and 160,000 years ago until about 30,000 years ago.
Their appearance was similar to modern humans: they could control fire and were adept toolmakers. They are now widely accepted however as a distinct evolutionary lineage from us.
Most archaeologists date their disappearance in Europe to about 30,000 years ago, about 10,000 years after the first modern humans arrived. The results of a new excavation in Gorham's Cave in Gibraltar published in Nature this morning forces a change of view.
Neanderthals survived at this southernmost tip of Europe until at least 28,000 years ago and possibly 24,000 years ago. This means humans and Neanderthals shared the Mediterranean landscape for much longer that expected. "Our results show that the Neanderthals survived in isolated refuges well after the arrival of modern humans in Europe," the authors report.
Neanderthal skulls and tools have been found from the UK to Croatia and from Russia to Portugal. Populations of Neanderthals disappeared very rapidly as modern humans began to arrive, however, as they fanned out to claim prime real estate from their more primitive cousins.
Clearly, modern humans had a competitive edge over their rivals, "perhaps from cultural practices such as improved clothing and more effective social networks", suggests a report that accompanies the research paper on Gorham's Cave.
It may be however that the Neanderthals managed to hold out that bit longer in refuges such as caves. They would have been battling against the incursion of modern humans but also the difficulties presented by a changing climate. An ice age still gripped the earth and hominid populations both modern and Neanderthal would have sought out territories around the Mediterranean where it was warmer.
The Neanderthals held up in Gorham's Cave had ready access to food supplies, the authors report. Gorham's Cave was surrounded by "a diverse community of plants and vertebrates on the sandy plains, open woodland and shrub land, wetlands, cliffs and coastal environments".
The scientists excavated a large 29sq m section of the cave floor. This brought them back in time past the Phoenician and Carthaginian cave occupations, past the later Stone Age and on back to the early Stone Age.
There, in the deepest part of the cave, termed level IV, they began encountering the characteristic Neanderthal "Mousterian" tools, a sure sign of Neanderthal habitation. The tools were found in clay layers that could be dated back to between 33,000 and 23,000 years ago.
"The dates suggest a favoured location that was visited repeatedly over many thousands of years," the authors write. "Its situation where natural light penetrates deep into the cave and where a high ceiling permits ventilation of smoke, is unique within the cave system, and hearths were made in the same location many times." Taking the data all together, the scientists argue that the Neanderthals occupied the site until 28,000 years, and possible as recently as 24,000 years ago.
These results, coupled with digs at ancient modern human sites suggest "the late survival of Neanderthals and the arrival of modern humans was a mosaic process in which pioneer groups of moderns and remnant groups of Neanderthals together occupied a highly heterogeneous region for several thousand years", the authors conclude.
They argue that the two populations interacted very little given that they were probably thinly scattered across the region. This meant that the two groups coexisted for a long time before the final disappearance of the Neanderthals.
The intriguing question remains, just how much did they interact? Did they meet or did they compete? Did they interbreed and if so did the Neanderthals contribute to the modern human gene pool?
The time may well have been too short for any significant or lasting interaction, the Nature reports suggest. There seems to have been little sharing of tool-making activity as the tool groups remain distinct, even if they were using the same basic materials, flint, chert and quartzite. Nor is there genetic evidence for any Neanderthal contribution to our gene pool.
If they did inbreed, there should be evidence for Neanderthal-modern hybrid offspring, and this evidence may exist in the Lagar Velho child. Found in Portugal and dated to 24,500 years ago, the remains were dismissed as a possible hybrid given the received wisdom that Neanderthals had disappeared 5,500 years before.
The discoveries in Gorham's Cave indicate that the Lagar Velho child might just be the proof that Neanderthals and moderns had some level of contact.