To aid in digestion, particularly of hard-to-digest leaves, they have multichambered, complex stomachs, making them the only primates with foregut fermentation.

Foregut fermenters use bacteria to detoxify plant compounds before reaching the intestine, where toxins can be absorbed.

In the silvery lutung (Trachypithecus cristatus) and the Northern plains gray langur (Semnopithecus entellus) females begin reproducing after around 3 years of age.

[7][2] The discordant gene tree topologies and divergence age estimates suggest that hybridization, particularly involving female introgression from Piliocolobus/Procolobus into Colobus and male introgression from Semnopithecus into Trachypithecus, played a prominent role in shaping the phylogenetic relationships of African and Asian colobine monkeys during their evolutionary history.

The earliest fossils of the genus in Eurasia are those of Mesopithecus found in Greece, dating to around 8.2 million years ago.

[10] Roos, Christian, et al. “Nuclear Versus Mitochondrial DNA: Evidence for Hybridization in Colobine Monkeys.” BMC Evolutionary Biology, vol.