Two partial skeletons unearthed from a cave in South Africa belong to a previously unclassified species of hominid that is shedding new light on the evolution of our own species, Homo sapiens, researchers say. The newly documented species, called Australopithecus sediba, was an upright walker that shared many physical traits with the earliest known Homo species—and its introduction into the fossil record might answer some key questions about what it means to be human.