Dispersal scenario for colobine monkeys. Colobines most likely originated in western Africa. After the successive split of Colobus (~10.9 mya) and a progenitor of Piliocolobus/Procolobus (~10.7 mya) from the ancestor of Asian colobines, gene flow between both African lineages via female introgression from the Piliocolobus/Procolobus progenitor into Colobus occurred until ~8.5 mya (displayed by red-dashed arrow). During the late Miocene, colobines invaded eastern Asia most likely via a route north of the Himalayas. After their arrival at the Hengduan Mountains, Asian colobines diversified into a lineage comprising a progenitor of the odd-nosed monkeys and Trachypithecus/Presbytis, and of Semnopithecus, which later colonized the Indian subcontinent. Shortly afterwards, Trachypithecus/Presbytis split off from odd-nosed monkeys, and migrated to southern mainland Asia, before finally both genera diverged from each other. In the region of today's Burma, Bangladesh and India, Semnopithecus and Trachypithecus came into secondary contact and hybridized until ~2.6 mya (displayed by red-dashed arrow). In the latest Miocene, odd-nosed monkeys migrated from China to the south and expanded their range into Indochina and Sundaland. Nasalis and Simias finally separated from each other 1.1-1.9 mya.
Roos et al. BMC Evolutionary Biology 2011 11:77 doi:10.1186/1471-2148-11-77