bison, cave of altamira, prehistoric art, upper paleolithic, engravings, steppe bison, prehistory, works of art, great technical mastery, artist, artistic, animal theme, animal, animals, art, artwork, reproduction, nature, old painting, 15500 and 13500 years before our era, lower magdalenian, memory of the past, of our ancestors, bison, bison, bison, bison, bison, prehistoric art, prehistory, prehistory, prehistory, art