CLIMATE, HETEROCHRONY, AND HUMAN-EVOLUTION

The Late Neogene African records of climatic change at the start of th e modern ice age, and of turnover in some mammalian groups including H ominidae, support the turnover pulse prediction. Many of the new speci es that appear 2.9-2.5 myr (millions of years) ago show similar suites of integrated character complexes, including larger bodies (consisten t with Bergmann's Rule) and relative reduction in some body parts (Ali en's Rule in the case of bodily extremities), together with enlargemen t of others including brains. I explore further the hypothesis (Vrba 1 994) that the same evolutionary event of growth prolongation, or time hypermorphosis, as it acts on characters with different ancestral grow th Profiles in the same body plan, can result in a major reorganizatio n-or ''shuffling''-of body proportions such that some characters becom e larger and others smaller, some hyperadult and others more juveniliz ed. I suggest that this hypothesis applies to major features of homini d evolution including hominine encephalization.