Human evolution is the evolutionary process leading up to the appearance of anatomically modern humans. The topic usually covers the evolutionary history of primates, in particular the genus Homo, and the emergence of Homo sapiens as a distinct species of hominids rather than studying the evolutionary history that led to primates. The study of human evolution involves many scientific disciplines, including physical anthropology, primatology, archaeology, paleontology, ethology, linguistics, evolutionary psychology, embryology and genetics. Genetic studies show that primates diverged from other mammals about 85 million years ago, in the Late Cretaceous period, and the earliest fossils appear in the Paleocene, around 55 million years ago. The family Hominidae diverged from the Hylobatidae family 15-20 million years ago, and around 14 million years ago, the Ponginae diverged from the Hominidae family. Bipedalism is the basic adaption of the Hominin line, and the earliest bipedal Hominin is considered to be either Sahelanthropus or Orrorin, with Ardipithecus, a full bipedal, coming somewhat later.