Among hyenas, only the spotted and striped hyenas have been known to become man-eaters. Hyenas are known to have preyed on humans in prehistory: Human hair has been found in fossilised hyena dung dating back 195,000 to 257,000 years. Some paleontologists believe that competition and predation by cave hyenas ("Crocuta crocuta spelaea") in Siberia was a significant factor in delaying human colonisation of Alaska. Hyenas may have occasionally stolen human kills, or entered campsites to drag off the young and weak, much like modern spotted hyenas in Africa. The oldest Alaskan human remains coincide with roughly the same time cave hyenas became extinct, leading certain paleontologists to infer that hyena predation was what prevented humans crossing the Bering strait earlier. Hyenas readily scavenge from human corpses; in Ethiopia, hyenas were reported to feed extensively on the corpses of victims of the 1960 attempted coup and the Red Terror. Hyenas habituated to scavenging on human corpses may develop bold behaviours towards living people: hyena attacks on people in southern Sudan increased during the Second Sudanese Civil War, when human corpses were readily available to them.