The researchers spent two weeks in Spain last year testing the new method in caves, and have just returned from another fortnight's expedition to sample nine more caves, including the so called 'Sistine Chapel of the Palaeolithic', Altamira cave.
"This lets us challenge assumptions about the age of cave art," says Alistair Pike, senior lecturer in archaeological sciences at Bristol University, who has helped develop the technique.
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Variability in traces of Middle Pleistocene hominid behavior in the Kapthurin Formation, Baringo, Kenya.
Indeed, Altamira's artists are renowned for how they used the natural contours of the cave to make their animal figures seem extra-real.