At the Cosquer Cave in France, deep sea divers discovered charcoal prints in the shape of hand stencils, thought to be at least 10,000 years old, on the walls of the undersea cave. Analysis of the prints, which appear in a number of different sizes, showed that they had been made with high-pressure charcoal no denser than that comprising the dense walls of the cave itself. However, scientists were unable to replicate the charcoal prints on the walls of the Cosquer Cave, because small pieces of charcoal from the cave walls do not maintain their consistency underwater and the prints were immediately washed away.
Which of the following, if true, would, taken together with the information above, provide the best basis for the claim that the prints were in fact charcoal handprints made by people during the Upper Paleolithic era, which ended 10,000 years ago?