On the Adaptive Radiation of Hominids

Abstract

A theory is advanced to explain the fragmentation of the Mio-Pliocene hominid Ramapithecus into a variety of known Plio-Pleistocene descendant lineages. The theory takes into account not only the mechanism underlying the proliferation of types from a species previously characterized by temporal and spatial stability, but also the relatively rapid differentiation of derivative lines. The latter phenomenon is remarkable for a creature with extended maturation and long generations. These factors, together with evolving emphasis on behavioral solutions to selective pressures, would ordinarily provide little capability or necessity for rapid genetic responses. The overall sequence of events was presumably triggered by changing ecological conditions which led to a discontinuous distribution of the last common ancestor of Plio-Pleistocene hominids. Rapid speciation ensued as a result of genetic drift and inbreeding, the latter sustained and reinforced by protocultural isolation.