Not surprisingly, these paintings attract tens of thousands of visitors every year. However, there is another aspect to this art that often escapes attention, but which is now providing scientists with fresh insights into our recent evolution. Instead of studying those magnificent galloping horses and bisons, researchers are investigating the symbols painted beside them. These signs are rarely mentioned in most studies of ancient cave art. Some are gathered in groups, some appear in ones or twos, while others are mixed in with the caves' images of animals. There are triangles, squares, full circles, semicircles, open angles, crosses and groups...