Scientists discover that cave art may predate humans
15 juin 2012
© The Global Edition of the New York Times
Stone age artists were painting red disks, hand prints, club-like symbols and geometric patterns on European cave walls long before previously thought, in some cases 10,000 years earlier, scientists reported Thursday after completing more reliable dating tests at prominent sites in northwestern Spain.
The ages of the art â€” 50 samples from 11 caves, some dated to more than 40,000 years ago â€” establish that this was probably the work of anatomically modern humans fairly soon after their arrival in Europe. Or, just possibly, and quite surprisingly, that of indigenous Neanderthals.
The findings seem to put an exclamation point on a run of recent discoveries: direct evidence from fossils that Homo sapiens were living in England 41,500 to 44,200 years ago and in Italy 43,000 to 45,000 years ago, and that they were making flutes in German caves about 42,000 years ago. Then there is the new genetic evidence of modern human-Neanderthal interbreeding, suggesting a closer relationship than had been generally thought.
The successful application of a newly refined uranium-thorium dating technique is also expected to send other scientists to other caves to see if they can reclaim prehistoric bragging rights.
In the new research, an international team led by Alistair W.G. Pike of the University of Bristol in England determined that the red disk in the El Castillo cave was part of the earliest known wall decorations, at a minimum of 40,800 years old. That makes it the earliest cave art found so far in Europe, perhaps 4,000 years older than the paintings at the Chauvet cave in France.
The hand prints common at several of the Spanish caves were stencils, probably made by blowing pigment on a hand placed against the cave wall. The oldest example, at El Castillo, proved to be at least 37,300 years old, which the scientists said â€˜â€˜considerably increases the antiquity of this motif and implies that depictions of the human hand were among the oldest art known in Europe.â€™â€™
At many-chambered Altamira, its splendor discovered in Spain in the 19th century, the researchers obtained a date of at least 35,600 years for a red clubshaped symbol. Archaeologists said this indicated that Altamiraâ€™s artistic tradition started about 10,000 years earlier than once estimated, and the cave appeared to have been revisited and painted many times over a span of 20,000 years.
In a report published online in the journal Science, Dr. Pike and his colleagues noted that the oldest dated art is â€˜â€˜nonfigurative and monochrome (red), supporting the notion that the earliest expression of art in Western Europe was less concerned with animal depiction and characterized by red dots, disks, line and hand stencils.â€™â€™ The more stunning murals of bison and horses came gradually, later.
Although the early dates coincide with recent evidence of a Homo sapiens presence in Europe, the scientists wrote that because 40,800 is only a minimum age â€˜â€˜it cannot be ruled out that the earliest painting were symbolic expressions of the Neanderthals,â€™â€™ who were living in that part of Spain until at least 42,000 years ago.
These close relatives of modern humans had lived in Europe and parts of Asia since at least 250,000 years ago, becoming extinct about 30,000 years ago, confined mostly in southern Iberia.
In another article for the journal, John Hellstrom of the University of Melbourne, an authority on dating prehistoric artifacts, praised the research. â€˜â€˜The scope of their study has allowed them to unambiguously identify a number of examples that challenge and overturn the previous understanding of that artâ€™s origin,â€™â€™ he wrote.
Dr. Hellstrom said that â€˜â€˜3 of the 50 examples dated show art to have been created in Spain at around (indeed possibly before) the time of the arrival of modern humans, bringing current ideas of the prehistory of human art in southern Europe into question.â€™â€™
At a teleconference for reporters on Wednesday, Dr. Pike said the older dates suggested three possible interpretations. One, Homo sapiens entered Europe with the tradition of cave art already in their culture. There is increasing evidence that their African ancestors had for thousands of years developed expressions of symbolic thinking in the form of perforated beads, engraved eggs shells and decorative pigments. Such has been the standard hypothesis.
Another scenario is that this artistic culture arose shortly after modern humans reached Europe. â€˜â€˜It might have been the result of competition for resources with Neanderthals,â€™â€™ Dr. Pike said. â€˜â€˜The rate of cultural innovation was accelerating, and this was a byproduct.â€™â€™
The third possibility, which the scientists said they had not anticipated at the start of their project, is that some of these earliest works of cave art might be attributed to Neanderthals. Until recently, archaeologists usually considered Neanderthals incapable of creating artistic works much beyond simple abstract markings and personal ornamentation.
Other scientists were expected to be skeptical, pending more evidence of even earlier dates for cave art or of painting associated with Neanderthal tools or fossils.
Eric Delson, a paleoanthropologist at Lehman College of the City University of New York, said, â€˜â€˜There is no need to hypothesize that Neanderthals created these paintings, as we have evidence of artistic Homo sapiens already in Western Europe.â€™â€™
But JoÃ£o ZilhÃ£o, a prehistorian and Neanderthal specialist at the University of Barcelona and a member of the research team, made a forceful defense of the hypothesis in the teleconference.
â€˜â€˜We have sufficient evidence to the effect that Neanderthals possessed a symbolic culture,â€™â€™ Dr. ZilhÃ£o said. â€˜â€˜They are close enough to modern humans to have interbred with us. This is sufficient to think about Neanderthals as fundamentally human beings with perhaps racial differences.â€™â€™
Saying that Neanderthals were â€˜â€˜more advanced than they have been given credit,â€™â€™ Dr. ZilhÃ£o conceded that their identification with any of the cave art â€˜â€˜cannot be proven at this time.â€™â€™
â€˜â€˜Itâ€™s just my gut feeling,â€™â€™ he added, â€˜â€˜and needs dates older than 42-, 43-, 44,000 years to sort it out.â€™â€™
The new research is â€˜â€˜most important,â€™â€™ Dr. Delson said, because it introduces a significant advance in techniques for more reliable, more precise and older dating of antiquities, especially cave art that in most cases does not lend itself to reliable dating by the usual radiocarbon methods. Dr. Hellstrom, in his article, recommended a wider application of the improved uranium-thorium dating method.
It is actually a 50-year-old but vastly improved technique. Cave art is typically found in limestone terrain. Water seeping into caves leaves deposits of calcium carbonate, or calcite, as stalactites and stalagmites or simpler crusts cover cave surfaces.
To date a painting under such a crust, researchers remove a piece of the calcite, dissolve the sample and extract traces of uranium and thorium atoms. Over time, the uranium in the crust has decayed into thorium. A measure of the ratio of uranium to thorium gives the minimum age of the art just beneath the crust.
This is an improvement over radiocarbon dating, which becomes less reliable at ages over 30,000 years and is not usable in dating art unless the pigment contained carbon, not mostly minerals. The uranium-thorium method has now been made more sensitive, so that calcite samples of just 10 milligrams, about as small as a grain of rice, can do the job.
Asked how the Neanderthal question could be resolved, Dr. Pike said, â€˜â€˜Simply go back and date more of these samples and find something that predates modern humans in Europe.â€™â€™
PubliÃ©: 2012-6-23 Mis Ã jour: 2012-6-23