During the late Paleolithic era, 10,000 to 50,000 years ago, humans roamed a vast steppe covering modern Europe, Asia and North America. These wandering hunters left behind myriad paintings on cave walls and artifacts depicting human figures and the large mammals of the day, including mam-moth, elk, bison and horses. Early interpretations cast the images as religious icons or magical totems, perhaps part of hunting or fertility rituals performed by shamans. Humans definitely produced repetitive, stylized iconography over the past 10,000 years, says R. Dale Guthrie, a paleobiologist emeritus at the University of Alaska-Fairbanks. "Paleolithic art isn't like that," he contends. "It was done in a more naturalistic way, [showing] real animals eating, copulating, braying or bellowing, biting." To Guthrie, a hunter and amateur artist himself, cave painters seem more like natural historians than shamans.