Final answer:
The main differences between australopithecines and pre-australopithecines lie in their physical characteristics, such as tooth size and sexual dimorphism.
Step-by-step explanation:
The main differences between australopithecines and pre-australopithecines can be identified in their physical characteristics. Pre-australopithecines, such as Australopithecus anamensis, had larger teeth and jaws compared to australopithecines like Australopithecus afarensis. Pre-australopithecines also exhibited sexual dimorphism, with males being up to 50% larger than females, while australopithecines had a reduced sexual dimorphism. Additionally, australopithecines had a more pronounced projection of the face (prognathism) than pre-australopithecines.