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| Following the extinction of the dinosaurs 65.5 million years ago, early mammal forms dispersed to new environments. Some early insectivores began to adapt more and more to life in the trees, developing grasping hands and binocular stereoscopic vision. These changes may have begun in response to the needs of insect predation and later been used to exploit additional food resources in a three-dimensional environment. The origins of primates can be traced to the primate-like mammals of the Paleocene epoch and the ancient prosimians of the Eocene. Primitive anthropoids evolved from a group of Eocene primates. The early Oligocene anthropoids ultimately gave rise to the separate lines of Old World monkeys and hominoids. The Miocene epoch is characterized by two major adaptive radiations. In the Early Miocene, primitive hominoid forms appeared in Africa. These forms, placed in the genus Proconsul, were similar in some ways to later apes but were also monkey-like in a number of features. They had jaws and teeth like those of later apes and lacked a tail. Their postcranial skeleton was generalized and primitive in a number of features. During the Middle Miocene, several new genera of hominoids evolved. These hominoids include the ancestors of present-day great apes and humans, although the specific evolutionary relationships between Miocene species and modern species are not clear at present. We are currently not able to identify precisely the common ancestor of the African apes and humans. Evidence from molecular dating supports a fairly recent split, roughly 6 million years ago. Although several genera of fossil apes could be a common ancestor (or related to a common ancestor), we cannot be definitive at this time. What is clear, however, is that there was extensive diversity in hominoids during the Miocene. |