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.[2] The Hominidae family diverged from the Hylobatidae (gibbon) family some 15–20 million years ago, and from the subfamily Ponginae (orangutans) about 14 million years ago.[3] The basic adaption of the hominin line is bipedalism. The earliest bipedal hominin is considered to be either Sahelanthropus or Orrorin; alternatively, either Sahelanthropus or Orrorin may instead be the last shared ancestor between chimps and humans. Ardipithecus, a full bipedal, arose somewhat later, and the early bipedals eventually evolved into the australopithecines, and later into the genus Homo.