The hominid cranial remains from the East Africa fossil site, Koobi Fora, comprise the richest available source of evidence for interpreting hominid taxonomy and phylogenetic history. This volume not only reviews the Koobi Fora evidence, but includes a morphological and morphometric survey ofall the other relevant Plio-Pleistocene fossil evidence for hominid evolution. These data include more than a quarter of a million measurements which are presented in detailed "reference tables". The data, and other information presented in the monograph, are used to generate a new interpretation ofthe nature and relationships of early hominid species. Two new taxa of the earlyHomo are introduced and defined, evidence is provided to support the re-introduction ofParanthropus, and a new phylogenetic hypothesis for hominid evolution is set out. This unique work is of special importance topaleontologists, paleoanthropologists as well as biologists interested in human evolution.