Evolution of the White-Headed Langur

Combining lines of evidence of paleontology and zoogeography of Asian langurs, we here offer a hypothesis of ancestral origin and evolution of China’s white-headed langur, divided into four phases. In the initial phase, during the extreme glaciation period in the Early Pleistocene Epoch, some ancient Javan langurs took the opportunity to emigrate northwards and entered the small land mass sandwiched between Zuo Jiang and Ming Jiang Rivers in Southwest China. Barricaded by the rivers, the Javan langur ancestors evolved independently into Chongzuo langurs (Trachypithecus chongzuosis). In the second phase, under the pressure of predacious animals, the Chongzuo langurs were forced to abandon their exclusive arboreal life and find natural refuges on the numerous precipices of Guangxi’s karst topography. In the third phase, on that extensive infertile land with a scant human population, the early white-headed langurs (T. leucocephalus) found sufficient suitable habitat to further evolve locally, adapting to coexist with humans. In a short, anthropogenic phase 4, from the 1950s to the year 2000, trees were brutally chopped and forests were recklessly exploited, which devastated the white-headed langurs’ natural habitat. Along with the rampant poaching activities, white-headed langurs were driven to an evolutionary bottleneck, at the brink of extinction.