Radiation and Evolution of Three Macaque Species, Macaca fascicularis, M. radiata and M. sinica, as Related to Geographic Changes in the Pleistocene of Southeast Asia

In a study of intrageneric variation in the genus Macaca , 72 dental and cranial measures of 11 species were examined morphometrically. Results indicate that 3 species, M. fascicularis, M. sinica and M. radiata , display close morphometric similarities. These species also share more similar patterns of sexual dimorphism compared with other macaques, regardless of which cranial part is considered. These findings differ from those of Fooden (1976) and 1980) and Delson (1980) concerning species-groups in Macaca , but are similar to findings from biochemistry, genetics and external features. These three species may thus have undergone common evolutionary processes and shared common ancestors. The crab-eating monkey, M. fascicularis , may have originated from southern India or the area that originally linked with Sri Lanka. They may have first dispersed eastwards, and then turned south, to penetrate southeastern Asia as they approached the geographic barriers caused by the up-lift of the Qinghai-Tibetan Plateau in the Pleistocene.