New tests of paintings in Spanish caves suggests that they were at least 15,000 years older tan previously thought, suggesting that they were created by Neanderthals, not Homo sapiens.

New tests show that crude Spanish cave paintings of a red sphere and handprints are the oldest in the world, so ancient they may not have been by modern man.

Some scientists say they might have even been made by the much-maligned Neanderthals, but others disagree.

Testing the coating of paintings in 11 Spanish caves, researchers found that one is at least 40,800 years old, which is at least 15,000 years older than previously thought. That makes them older than the more famous French cave paintings by thousands of years.

Scientists dated the Spanish cave paintings by measuring the decay of uranium atoms, instead of traditional carbon-dating, according to a report released Thursday by the journal Science. The paintings were first discovered in the 1870s.

The oldest of the paintings is a red sphere from a cave called El Castillo. About 25 outlined handprints in another cave are at least 37,300 years old. Slightly younger paintings include horses.

Cave paintings are "one of the most exquisite examples of human symbolic behavior," said study co-author Joao Zilhao, an anthropologist at the University of Barcelona. "And that, that's what makes us human."

There is older sculpture and other portable art. Before the latest test, the oldest known cave paintings were those France's Chauvet cave, considered between 32,000 and 37,000 years old.

What makes the dating of the Spanish cave paintings important is that it's around the time when modern humans first came into Europe from Africa.

Study authors say they could have been from modern man decorating their new digs or they could have been the working of the long-time former tenant of Europe: the Neanderthal. Scientists said Neanderthals were in Europe from about 250,000 years ago until about 35,000 years ago. Modern humans arrived in Europe about 41,000 to 45,000 years ago — with some claims they moved in even earlier — and replaced Neanderthals.

"There is a strong chance that these results imply Neanderthal authorship," Zilhao said. "But I will not say we have proven it because we haven't."