CHANGES OF TOOTH DEVELOPMENT IN HOMINIDS DURING THE PLIOPLEISTOCENE -VARIATIONS OF TOOTH FORMATION CHARACTERISTICS

Tendencies in tooth formation of Plio-Pleistocene hominids have been s uggested but without regard to stratigraphic levels. Our aim is to ana lyse the modifications of tooth development over time in 21 premolars and 45 molars from Member B (3.36 Myrs) to Submember G9 (2.1 Myrs) of the Omo Group (Ethiopia). The modifications of enamel microstructure c haracteristics were analysed with Anova and correlations. Only the num ber of appositional striae increased between 3.36 and 2.1 Myrs in both premolars and molars. Other characteristics were modified over a shor t period, especially in premolars or show sudden changes, principally in molars. The more important development of the appositional stage in dicates new occlusal constraints as a result Of more abrasive diet whi ch is in agreement with changes observed in fauna and flora. This chan ge appears in its extreme form in robust australopithecines with a thi cker enamel, but a more important development of the appositional stag e over time characterizes all Plio-Pleistocene hominids.