William H. Kimbel

The Importance of Species Taxa in Paleoanthropology and an Argument for the Phylogenetic Concept of the Species Category

Paleoanthropology attempts to describe the diversity of extinct primate forms, to interpret this diversity in a phylogenetic framework based on the distribution of shared evolutionary novelties, and to explain the emergence and transformation of novelties in terms of a positive causal relationship between changes in structure/function and enhanced organismal fitness (i.e., adaptation). These components may be viewed as a sequence of steps toward a “complete” explanation of evolutionary change, each step logically contingent on those preceding it. Thus, hypotheses seeking to explain the adaptive basis of evolutionary morphological change necessarily depend on the prior acceptance of a hypothesis of vectored phylogenetic change. In turn, a phylogenetic hypothesis must be grounded in some theoretical concept of the units of diversity, among which the pattern of phylogenetic relationships is sought.

Identification of a Partial Cranium of Australopithecus afarensis from the Koobi Fora Formation, Kenya

Abstract The parieto-occipital morphology of a partial hominid cranium (KNM-ER 2602) from the Pliocene Tulu Bor Member of the Koobi Fora Formation, Kenya, identifies this specimen as Australopithecus afarensis. At approximately 3·3 Myr (million years) old, this Kenyan hominid is contemporary with Hadar A. afarensis, and fills an important geographic gap between the Ethiopian and Tanzanian distributions of this species.