ABSTRACT
Several evolutionary histories of Australopithecus and Homo species have been presented during the past decade (e.g., Johanson and White, 1979; Tobias, 1980; White et al., 1981; Olson, 1981), and the recent discovery of a late Pliocene “ robust” cranium in the Lake Turkana Basin (Walker et al., 1986) has led to improved phylogenetic schemes. One such scheme is shown in Fig. 24.1. Eventually, as the phylogeny of hominids becomes more firmly known, the chronology and underlying causes of their evolutionary history will emerge. Meanwhile, most current hominid phylogenies show more than one splitting event in late Pliocene time between 3.0 and 2.0 Myr (Fig. 24.1) (Grine, this volume, chapter 30; Kimbel et al., this volume, chapter 16; Walker and Leakey, this volume, chapter 15; Wood, this volume, chapter 17).
