Abstract:

Rudapithecus hungaricus, a late Miocene great ape from Rudabánya, Hungary, is a key taxon for understanding the origin, evolution, and dispersal of Homininae. This species has been hypothesized to be capable of processing hard food items. To test this hypothesis, we conducted three-dimensional analyses of enamel thickness (ET) across eight Rudapithecus teeth (including four premolars and four molars) and estimated bite force (BF) of four molars using μCT data. Two enamel thickness indices were measured: Three-dimensional average enamel thickness (3DAET) and the ratio of enamel-thickness to dentine-thickness (3DRED). According to Chai (2018), we measured dentine horn angle (DHA) and cuspal enamel thickness (CET) to estimate BF. Then we compared the results with that of extant great apes (Pan, Gorilla, and Pongo), including 61 ET measurements and 18 BF estimates. Results reveal that the average ET of Rudapithecus is greater in molars than in premolars. While Rudapithecus is broadly akin to Pan with respect to premolar ET, its molar ET shows a pattern more similar to Pongo. Furthermore, the average molar BF of Rudapithecus is 469.66N, which is larger than that of Pan (353.56 N), smaller than that of Gorilla (1023.06 N), and approximately equal to Pongo (499.62 N). Considering a high similarity between Rudapithecus and Pongo regarding molar ET and molar BF, and previous studies have shown that Pongo can process both tough and hard foods, thus our results support the hypothesis that Rudapithecus had the capability of processing hard foods. However, our results do not necessarily suggest that Rudapithecus had an overall tougher and/or harder diet. Which foods a species have actually eaten depends on a variety of factors such as the food processing capabilities, environmental variability, the accessibility of preferred foods, and the competition with other species. Combined with previous dietary researches, it is possible that the functional significance of thick enamel and great molar BF presented in Rudapithecus is to ensure basic energy intake by processing infrequently-exploited exigent mechanically challenging foods (hard and/or tough foods) during periods of fruit scarcity. To advance the understanding of Rudapithecus feeding ecology, future researches may need to incorporate direct dietary evidence derived from various methods such as phytolith, calcium isotope, and dental chipping analyses.

Key words: Rudapithecus hungaricus, 3D enamel thickness, bite force, fallback food