Abstract: The processes of formation and diversification of modern human populations resulted in a series of physical characteristics in different geographic regions. These characteristics were consequently important in tracing population affinity. As an essential part of molar morphometrics, the relative cuspal area has gained intense interest due to its value in studies of both human evolution and population affinity. However, it was not clear whether the regional variation of M1 relative cuspal areas exists among different populations. Based on measurements and comparisons of relative cuspal areas of 208 M1s, the present study revealed that recent Asian and African populations were significant different from each other in relative sizes of all four cusps. Specifically, Asians had a relatively large protocone and paracone, and a relatively small metacone and hypocone. Ranges of variations of all four cusps were larger in African specimens than in Asian ones, especially the relative protocone and hypocone sizes. Discriminant analysis could correctly discriminate 69.2% of the specimens into their original groups. After comparisons with corresponding data of fossil hominins, recent Africans were found to be more close to early forms of human evolution in relative cuspal areas of protocone and hypocone, as well as in the proportion of paracone/metacone. Diversification of recent Asian and African populations in the M1 relative cuspal areas can be traced back at least to the early Holocene, and the acquiring of a more precise diversification time required involvement of hominins of Late and even Middle Pleistocene. The high degree of heterogeneity and relative primitiveness of recent African specimens revealed by the present study need to be ascertained through further studies.

Key words: Modern human; Upper first molar; Relative cuspal area; Heterogeneity; Primitiveness