Abstract: The relationship between hominins in Europe and Asia has been the concern of human evolutionary studies for a while. Based on morphological studies of hominin fossils, some researchers believe that there was gene flow between these hominins during the Middle and Late Pleistocene based on morphological evidence. However there have been different understandings of some of aspects of population affinity, function, development and homology. In this research, occurrences and expression patterns of Carabelli’s cusp of 98 upper molars of Chinese hominins were analyzed in both the outer enamel surface (OES) and enamel dentine junction (EDJ) based on micro-CT scanning. Comparisons with the specimens of African and European hominins were also considered. Our results show that Carabelli’s cusp has a high frequency in Chinese hominins (27.6%~62.5%) including different expression patterns, specifically the cingulum-protocone crest and horizontal groove across the crown lingual surface or shelf-like Carabelli’s cusp, which usually occur in chimpanzee and African early hominins but are also identified in a number of upper molars of Chinese hominins. With these results, we support the view that Carabelli’s cusp is an ancient or primitive feature that evolved from apes until modern humans. The expression patterns of Carabelli’s cusp in Chinese hominins suggest that this trait is possibly a remnant of the ancient or primitive feature. This study shows that Carabelli’s cusp has a high frequency in both Chinese and European hominins but is more pronounced in Chinese hominins than its European counterparts. Therefore, there is no reliable evidence to currently support Carabelli’s cusp as a morphological feature indicative of gene flow between Chinese and European hominins.

Key words: Carabelli’s cusp; Dentition; Paleoanthropology; Gene flow