20. Catarrhine Origins

Summary

Paleontological evidence demonstrates that early catarrhines (i.e., the clade comprising Old World monkeys, apes and humans) first occurred in Afro-Arabia during the Early Oligocene and were restricted to this zoogeographic region until the Early Miocene. The estimated divergence date for catarrhines and platyrrhines, based on molecular evidence, indicates that catarrhines may have had an even earlier phylogenetic history that extends back to about 40-44 Ma into the Middle Eocene. During this long period of isolation in Afro-Arabia, several major clades of catarrhines, including the Propliopithecoidea, Pliopithecoidea, Saadanioidea, Dendropithecoidea, Cercopithecoidea, and Hominoidea, originated. The Cercopithecoidea and the Hominoidea comprise all extant catarrhines, and are referred to as crown catarrhines. The Propliopithecoidea, Pliopithecoidea, Saadanioidea, and Dendropithecoidea are extinct lineages of catarrhines that diverged prior to the last common ancestor of hominoids and cercopithecoids, and are referred to as stem catarrhines.