A human skull from a Romanian bear cave is shaking up ideas about ancient sex. The Homo sapiens skull has a distinctive feature previously found only in Neandertals, providing further evidence of interbreeding between the two species, according to a new study. The human cranium was found during World War II mining operations in 1942, in a cave littered with Ice Age cave bear remains. Recently the fossil was radiocarbon dated to 33,000 years ago and thoroughly examined, revealing the controversial anatomical feature. The otherwise human skull has a groove at the base of the back of the skull, just...