Scientists have discovered Europe's oldest cave artwork - painted by our ancestors at least 40,800 years ago.
The Palaeolithic paintings in Northern Spain have been precisely dated for the first time proving the art form actually began in Europe 10,000 years earlier than originally thought.
This means the cave paintings were created by either the first anatomically modern humans in the area - first thought to exist 41,500 years ago - or by Neanderthals.
Experts were able to work out the age of the paintings by dating the formulation of tiny stalactites on top of the art - using the radioactive decay of uranium.
They examined a total of 11 caves in Northern Spain, including the UNESCO World Heritage sites of Altamira, El Castillo and Tito Bustillo.
Hand stencils and disks made by blowing paint on to the wall in the El Castillo cave in Northern Spain proved to dated back to at least 40,800 years.
A large club-shaped symbol in the famous polychrome chamber in Altamira was found to be at least 35,600 years old - showing painting started 10,000 years earlier than believed.
The cave was revisited and painted on a number of different occasions over a period spanning a staggering 20,000 years.
Dr Alistair Pike, of the University of Bristol, said the paintings were up to 10,000 years older than previous examples from France.
He said: 'Evidence for modern humans in Northern Spain dates back to 41,500 years ago, and before them were Neanderthals.
'Our results show that either modern humans arrived with painting already part of their cultural activity or it developed very shortly after, perhaps in response to competition with Neanderthals - or perhaps the art is Neanderthal art.'
He added that the creation of art is considered an important marker for the evolution of modern thinking and behaving and could be linked with the development of language.
Dr Pike said: 'We see evidence for earlier human symbolism in the form of perforated beads, engraved egg shells and pigments in Africa 70-100,000 years ago, but it appears that the earliest cave paintings are in Europe.
'One argument for its development here is that competition for resources with Neanderthals provoked increased cultural innovation from the earliest groups of modern humans in order to survive.
'Alternatively, cave painting started before the arrival of modern humans, and was done by Neanderthals.
'That would be a fantastic find as it would mean the hand stencils on the walls of the caves are outlines of Neanderthals' hands, but we will need to date more examples to see if this is the case.'
The scientists were forced to use the uranium method as the paintings lacked organic pigments or binders suitable for radiocarbon dating.
And even if there is organic material - such as charcoal pigments - only small samples can be used for dating to minimise damage.
This can cause contamination, leading to an inaccurate result.
Instead, the international team measured uranium isotypes in the thin calcite flowstone growths which had formed on the surfaces of the paintings to date the art.
The method, known as uranium-series disequilibrium, is used in Earth Sciences to accurately date ancient objects.
Dr Dick Hoffmann, of the National Centre for the Investigation of Human Evolution in Burgos, Spain, said: 'The key development was our method to date tiny calcium carbonate deposits similar to stalactites.
'We can now date samples of just 10 milligrams - about as small as a grain of rice. This has allowed us to find samples that had formed directly on top of hundreds of paintings, whereas the larger stalactites were much less frequent.'
Cave art specialist Dr Paul Pettitt of the University of Sheffield, UK added: 'Until now our understanding of the age of cave art was sketchy at best; now we have firmly extended the earliest age of European cave art back by several thousand years, to the time of the last Neanderthals and earliest Homo sapiens.
'These earliest images do not represent animals, and suggest that the earliest art was non-figurative, which may have significant implications for how art evolved.'
The research 'U-series of Palaeolithic Art in 11 Caves in Spain' is published in Science.