Perhaps it was too much to hope that we should get very far with answers to the questions: What is man?; where, when and why did he begin? But with a sound basis of chronology, such as was provided by Curtis, the dates by which several important stages had been reached can now be fixed more definitely than before. Evidence such as that of Tuttle and Leakey establishes that some hominids were certainly walking bipedally before 3.0 Ma ago. But as Simons asked ‘How long before?’ The conditions for bipedalism may have first arisen after the marked cooling ca .14 Ma ago that led to formation of an Antarctic ice cap, producing a fall in sea levels and drier conditions generally (Kennet 1977). Much forest was then replaced by open prairie and many cursorial herbivores and carnivores appeared. Such circumstances would have favoured development of the earliest terrestrial anthropoids, who were probably still partly climbers, as indicated by the curved phalanges.