Scientists have already become remarkably good at answering two other questions about cave art. Chemical analysis can identify pigments such as red ochre and charcoal, while advances in dating techniques have steadily pushed the origins of cave art further back in time. Scientists sampled painted and unpainted cave walls at 11 sites across Spain and Portugal. Ancient human DNA turned up in the rock itself, demonstrating for the first time that cave walls can preserve genetic material for thousands of years. It does, however, suggest that cave walls preserve more than paintings.