A reproduction of the Altamira Polychrome Ceiling in the National Museum and Research Center of Altamira. The famous polychrome bison can be seen painted over earlier red symbols dated to earlier than 35,600 years ago. | Video © National Museum and Research Centre of Altamira
Researchers have shown that some cave paintings in northwestern Spain are older than expected, which raises some questions about the artists responsible. According to Alistair Pike from the University of Bristol and colleagues from England and Spain, the tradition of decorating caves with colored pigments must have begun in Spain more than 40,000 years ago—an age that coincides with the arrival of modern humans in Europe.
But the antiquity of the cave paintings in Spain means that Pike and his colleagues can’t dismiss the possibility that Neandertals created the ancient works of art, since they were also living in the region when Homo sapiens arrived.
The researchers dated calcite deposits associated with 50 paintings in 11 different caves. These deposits, which cannot be older than the cave art itself when they overlie the cave paintings, provide a minimum age for the artwork. The age of the calcite was determined by a technique known as uranium-thorium (U-Th) dating, which is less destructive than radiocarbon dating and only requires a few milligrams of sample material.
The researchers’ results are published in the 15 June issue of the journal Science.
“Science is excited to be publishing this paper because it both develops an approach for dating cave art and provides a rich series of dates on art in numerous caves,” said Brooks Hanson, the journal’s deputy editor for the physical sciences.
Cave paintings are among some of the earliest examples of art and human symbolic behavior, but inconsistencies produced by radiocarbon dating techniques have prevented archaeologists from understanding how different styles and practices developed. The U-Th dating technique used by Pike and his colleagues, however, has improved enough over the past few decades to produce consistently accurate results from extremely small sample sizes.
“We had a real problem providing reliable chronologies for cave art, and one of the reasons was that one of the primary dating methods that archaeologists use—radiocarbon dating—is not suitable for paintings that are made purely with mineral pigments or engravings,” said Pike during a 13 June press teleconference. “So, we attempted to circumvent these problems by using a completely different method that is based on the radioactive decay of uranium.”
“These cave paintings have, growing on top of them, very thin calcium carbonate crusts that are formed by the same processes that form stalagmites and stalactites,” he explained. “They incorporate tiny amounts of radioactive uranium, which decays to thorium, and it’s the measurement of this build-up of thorium that can tell us how long ago those crusts formed.”
The researchers visited caves in northern Spain, including the UNESCO World Heritage sites at Altamira, El Castillo, and Tito Bustillo, and collected rice grain-sized samples of cave paintings that represent different artistic styles. With U-Th dating, they identified a small cluster of paintings that coincide with the arrival of early modern humans in Europe.
According to Pike and his colleagues, one particular cave painting of a red disk from El Castillo is at least 40,800 years old, whereas another—an ancient hand stencil—is at least 37,300 years old, and a club-like symbol from Altamira appears to be more than 35,600 years old.
The age of these cave paintings helps to document how artistic styles evolved over time, they say. And since the cave paintings were created around the same time that modern humans and Neandertals lived on the continent, Pike and his colleagues suggest that it’s currently impossible to assign them to specific artists.
Alistair Pike of Bristol University removes calcite samples from the cave paintings for dating. As little as 10 milligrams—about the size of a grain of rice—are required. | Image courtesy of Marcos Garcia Diez
“After 150 years of Paleolithic archaeology, we have no evidence of modern humans in Europe that predates 41,500 years ago, and the earliest directly dated modern human remains are those from the Romanian cave site of Oase, which date to about 40,500 years ago,” said Joao Zilhão, a co-author of the Science report.
“So, simply by comparing the dates of the earliest modern human remains currently known in Europe with the minimum age of El Castillo art, we can already say that the cave art predates modern humans to the extent of the currently available evidence,” he continued. “But we cannot make the statement with 100% certainty that this earliest abstract art—of symbols and hand stencils—relates to Neandertals.”
The ancient artwork could mean instead that cave painting was already part of modern humans’ repertoire when they reached Europe. To know for sure, researchers will have to keep searching for even older cave art.
“If these samples were painted by Neandertals, it would be a fairly straightforward thing to prove that they were,” said Pike. “Quite simply, all we have to do is go back, date more of these samples and find a date that predates the arrival of modern humans in Europe.”
“Bear in mind that we have only sampled a tiny percentage of available cave paintings in Europe,” he said. “And we have an ongoing program that, at the moment, is targeting quite specifically hand stencils, red disks, and red symbols in order to see whether or not dates that are significantly older than 41,000 or 42,000 years can be found in similar samples of other paintings.”
Read the abstract, “U-Series Dating of Paleolithic Art in 11 Caves in Spain,” by Alistair Pike and colleagues.
Listen to the research team discuss its findings during a 13 June press teleconference.