fossil primate genus dating from the Middle and Late Miocene epochs (about 16.6 to 5.3 million years ago). For a time in the 1960s and '70s Ramapithecus was thought to be the first direct ancestor of modern humans.

The first Ramapithecus fossils (fragments of an upper jaw and some teeth) were discovered in 1932 in fossil deposits in the Siwālik hills of northern India. No significance was attached to these fossils until 1960, when Elwyn Simons of Yale University began studying them and fit the jaw fragments together. Based on his observations of the shape of the jaw and of the dentition—which he thought were transitional between those of apes and humans—Simons advanced the theory that Ramapithecus represented the first step in the evolutionary divergence of humans from the common hominoid stock that produced modern apes and humans.

Simons's theory was strongly supported by his student David Pilbeam, and it soon gained wide acceptance among anthropologists. The age of the fossils (about 14 million years) fit well with the then-prevailing notion that the ape-human split had occurred at least 15 million years ago. The first challenge to the theory came in the late 1960s from biochemist Allan Wilson and anthropologist Vincent Sarich, who, at the University of California at Berkeley, had been comparing the molecular chemistry of albumins (blood proteins) among various animal species. They concluded that the ape-human divergence must have occurred much later than the dates for Ramapithecus (it is now thought that the final split took place some 6 to 8 million years ago).

Wilson and Sarich's argument was initially dismissed by anthropologists, but biochemical and fossil evidence mounted in favour of it. Finally, in 1976, Pilbeam discovered a complete Ramapithecus jaw, not far from the initial fossil find, that had a distinctive V shape and thus differed markedly from the parabolic shape of hominid jaws. He soon repudiated his belief in Ramapithecus as a human ancestor, and the theory was largely abandoned by the early 1980s. Ramapithecus fossils subsequently were found to resemble those of the fossil primate genus Sivapithecus (q.v.), which is now regarded as ancestral to the orangutan; the belief also grew that Ramapithecus probably should be included in the Sivapithecus genus.