Scientists using a new dating technique reported Thursday that many of the most famous cave paintings in Spain are thousands of years older than previously thought - ancient enough to have been created not by Homo sapiens like ourselves but by Neanderthals, the species that lived in Europe long before the newcomers arrived from Africa.

"It is very important stuff, and one more piece in the puzzle minimizing the differences between the behavioral/cognitive capabilities and actual behaviors of Neanderthals and modern humans," said anthropologist Erik Trinkaus of Washington University in St. Louis, who has studied Neanderthals for decades and was not involved in the new study.

Figuring out who painted the hand stencils, shapes, and animals in such famous caves as Altamira in Spain could shed light on several enigmas of human evolution.

Cave art is a form of symbolic thinking: the depictions on walls stood for real animals and possibly (in the case of shapes) for something abstract. It is thus an important clue to when this cognitive capacity - which underlies language, abstract thought and other higher brain functions - arose and whether it evolved separately in two parallel human lineages.

"We are interested in knowing when people became more like us," said paleoanthropologist Eric Delson of Lehman College in New York, who lauded the new study as "a very nice piece of work." Cave painting, he said, "is an example of symbolic behavior, which makes us human."

DISKS AND STENCILS

For the new study, published in Science, researchers from eight universities and research institutions in Europe took minute samples - 10 grams, about the size as a grain of rice - from thin layers of calcite that coat paintings on the walls of 11 caves in northwestern Spain. This crust contains trace amounts of radioactive uranium. Measuring how much uranium has decayed into thorium reveals how old the layer is. That, in turn, gives a minimum age of the painting beneath it. In other words, the painting must be older.

Using this technique, archaeologist Alistair Pike of the University of Bristol and colleagues determined the ages of 50 works of cave art. Most lay beneath calcite less than 25,000 years old. But five, the scientists wrote, were "more interesting."

A large club-like shape at Altamira is at least 35,600 years old, millennia older than previous estimates, they report. Stencils made by blowing pigment onto a hand pressed against a wall at El Castillo is more than 37,300 years old, also thousands of years older than previously calculated.

The biggest surprise was the age of several large red disks, also made by blowing pigment, at El Castillo: at least 40,800 years. Dozens of such disks and 40 hand stencils are in the same panel, along with rectangles and ovals, suggesting that 40,800 is the minimum age of the entire composition.

That makes the painting, which would not look out of place in a Joan Miro retrospective, "Europe's oldest known art by at least 4,000 years," said Pike said at a news conference Wednesday.

That extreme age raises the highly charged question of who the artists were. If Homo sapiens, it suggests the newcomers developed their painterly talents right after they walked to Europe from Africa via the Levant. "But why would that ability develop in Europe and not Africa" where no cave paintings have been found, asked Pike.

The more controversial possibility is that the art is the work of Neanderthals (or "Neandertals," in scientists' preferred spelling). "Symbolic culture clearly existed among Neanderthals," said archaeologist Joao Zilhão of the University of Barcelona, the study's senior author. Given that, "it wouldn't be surprising if they were Europe's first cave artists."

That is not as outrageous a suggestion as it would have been 10 years ago. Anthropologists have recently made several discoveries showing that Neanderthals were capable of symbolic thought.

JEWELRY AND GRAVES

Neanderthals buried their dead and placed objects in the graves, "as if they recognized some stage after death," said Lehman's Delson. They also painted scallop shells and cockleshells, scientists excavating caves in Spain discovered in 2010. That was the first hard evidence Neanderthals created jewelry, which scientists call evidence of symbolic thinking ("this painted shell pendant means I belong to this clan"). Such discoveries put the nail in the coffin of the idea that Neanderthals were mentally inferior to Homo sapiens, leading to their demise.

"There is no documentable difference in symbolic behavior between Neanderthals and modern humans at any given time period," said Trinkaus.

The crux of the who-were-the-artists controversy therefore comes down to this: were Neanderthals the only humans in Europe when the cave art was made?

Zilhão believes the most solid evidence dates the arrival of modern humans to 40,500 years ago. If the cave art is at minimum 40,800 years old - and probably centuries if not millennia older - "that is enough to place the paintings in a time period when there were no modern humans in Europe," said Zilhão. "It cannot be proven at this time, but that's my gut feeling."

Others disagree. "The oldest Homo sapiens in Europe may date from 45,000 to 42,000 years ago," retorted Delson in an interview with Reuters. He said a 2011 study found fossils of that age in England and Italy. "There is no need to hypothesize that Neanderthals created these paintings."

That 2011 claim, too, is controversial, however. Critics argue that the fossils are actually Neanderthals. Last month in Science, Zilhão accused rivals of being "on a mission from God to put modern humans in Europe early enough" to be the creators of ancient art and other artifacts, "putting Neanderthals back where they ‘deserve' to be."

For laypeople who don't care about the academic sniping, the possibility that the hand stencils and other cave paintings were made by long-gone Neanderthals offers a certain thrill. It means, said Pike, "that anyone can walk into El Castillo and see a Neanderthal hand on the wall."

(Editing by Doina Chiacu)

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