The Geological Context of Human Evolution

Abstract

Geological processes and changes during the last 15 million years helped to shape the course of human evolution, in the same way that environments influenced the adaptation or extinction of all organisms. This is obvious in a broad sense, but just how geology influenced our emergence as a unique species is not obvious. With the recent increase in understanding of global tectonic and climatic patterns for the later Cenozoic and the recovery of an ever-increasing fossil and contextual record for human evolution, we are beginning to see how geological processes and the evolution of Homo sapiens may fit together. This paper focuses on the fossil and paleoenvironmental record for the larger hominoids over the period between 15 and 1 m.y. B.P. This time interval encompasses the major evolutionary changes that transformed one of the many primitive apelike primates that existed before 15 m.y. B.P. into the unmistakable Homo of 1 m.y. B.P. Hominoid refers to the superfamily Homi­ noidea, which includes the Hylobatidae (gibbons), Pliopithecidae (small fossil apes), Pongidae (apes), and Hominidae (humans and their closest fossil rela­ tives) (65, 80). In this paper hominoid is used as the inclusive term for the larger-bodied fossil Pondigae and Hominidae, which are of most interest to the evolutionary history of Homo sapiens . Familiar genera included under this label are Homo, Australopithecus, Sivapithecus, Ramapithecus, Gigan­ topithecus, Pango, Dryopithecus, and Proconsul. Gorilla and Pan also be­ long with the larger hominoids, although they have no fossil record and are not