Transformations of the nervous, masticatory, locomotor and manipulatory systems, with accompanying functional changes, marked the emergence of the Hominidae and of the genus Homo. Various systems evolved in a mosaic fashion. The manipulatory and locomotor systems hominized early, probably with the emergence of the hominid family. Major changes of brain form and size occurred later, with the emergence of Homo. The functional counterpart of brain change is often thought of as cultural behaviour (material and non-material). However, the evolution of a propensity for culture would not alone have ensured the perpetuation of culture. Only an advanced mechanism for social transmission could have handed on the culture itself: evolving speech was such an advanced mechanism. Direct and indirect evidence suggests that emergent Homo (though not Australopithecus) possessed at least the rudiments of a speech faculty about 2 Ma ago. Thereafter, biological and cultural evolution were in a positive reciprocal feedback relationship. In this autocatalytic system, speech was a crucial component: by making possible spoken teaching and learning, it enabled culture to evolve beyond what could be conveyed by grunts, snorts or nudges.