fossil primate genus dating from the Miocene Epoch (23.7 to 5.3 million years ago) and thought to be the direct ancestor of the orangutan. Sivapithecus is closely related to Ramapithecus, and fossils of the two primates have often been recovered from the same deposits in the Siwālik Hills of northern Pakistan. Other Sivapithecus remains have been found at sites in Turkey, Pakistan, China, Greece, and Kenya. Some authorities maintain that Sivapithecus and Ramapithecus are in fact the same species. Though Sivapithecus was slightly larger than Ramapithecus, it was only a small-to-medium-sized ape about the size of a modern chimpanzee. The fossil remains of Sivapithecus reveal that it shared many of the same specialized facial features of the orangutan—i.e., eyes set narrowly apart, a concave face, a smooth nasal floor, large zygomatic bones, and enlarged central incisors.

Sivapithecus' place in primate evolution was poorly understood until the 1980s. Prior to this, the genus, along with Ramapithecus, was interpreted as having both apelike and humanlike features and thus was presumed to be a possible first step in the evolutionary divergence of humans from the common hominoid stock of the apes. But new Sivapithecus finds and the reinterpretation of existing remains convinced most authorities in the 1980s that Sivapithecus was the ancestor of the modern orangutan and diverged from the common lineage of the African apes (i.e., chimpanzees and gorillas) and humans more than 13 million years ago. The earliest Sivapithecus remains found so far are about 17 million years old, and the most recent are about 8 million years old.