Abstract The degree of attrition on the mandibular deciduous teeth of 35 great apes, between 6 months and 5 years of age, was recorded by direct observation of each tooth. Specimens of Gorilla show markedly advanced attrition in relation to specimens Pan or Pongo of similar age. No differences in attrition could be detected between these last two species. It is argued that the heavy gorilla attrition is unlikely to be related to relative enamel thickness, to eruption sequence, to the length of time the deciduous teeth are in functional occlusion in the mouth, or to cusp morphology. Rather the extreme gorilla attrition seems to be related either to early weaning in this species or to diet or to a combination of these factors. It is also noted that Paranthropus and Australopithecus africanus infants seem to follow the same pattern of increased attrition on their deciduous dentition earlier in the growth period as does Gorilla . If this heavy attrition is related, even in part, to early weaning in these hominids, it could also reflect a relatively short interbirth interval as suggested for Gorilla . This provides some evidence to suggest that these fossils would have had a relatively faster reproductive rate than inferred for either earlier ( Australopithecus afarensis ) or later hominids.