A contribution to the question of early Homo in southern Africa : researches into dating, taxonomy and phylogeny reconstruction

Abstract

The origin of genus Homo is a core problem in contemporary palaeoanthropology. Most research in early hominid studies has hitherto focussed on the bearing of East African hominids on this problem. This dissertation examines the importance of southern African early Homo to this question, and provides a comprehensive assessment of the age, morphology, taxonomic status and evolutionary relationships of these fossils. This study establishes the reliability of electron spin resonance (ESR) dating of tooth enamel for samples from South African early hominid cave sites. These sites are characterised by a number of geological and geochemical factors, including low sample uranium concentrations, which allow for the dating of Upper Pliocene and Lower Pleistocene samples with this method. Given sufficient understanding o f the depositional history and provenance of fossil teeth, age estimates can be derived which are consistent with established views of the antiquity of early hominids from these deposits. This study marks the first comprehensive numerical dating of the sites of Sterkfontein and Swartkrans, and experimental dating of Kromdraai and Gladysvale. It also combines the first direct dating of australopithecine remains to provide the first chronological framework for early hominid evolution in southern Africa based on numerical dating. Remains from Sterkfontein previously attributed to A. africanus, but H. africanus in this study, are dated from around 3.0 to 2.0 Ma. Homo habilis from Sterkfontein, or Homo sp. nov. in this study, is dated around 1.6-1.7 Ma. Paranthropus robustus (SKW 11) from the “Hanging Remnant” of Member 1 of the Swartkrans Formation has been directly dated in this study to around 2.0-2.1 Ma. The estimated age of SKW 11, and faunal samples from this unit, provide an inferential age for early Homo from the “Hanging Remnant” of around 2.0 Ma. ESR dating of the hominid bearing unit of the Kromdraai B cave site suggests P. robustus survived well into the Middle Pleistocene. If the single tooth dated in this study is representative of the stratigraphic unit as a whole, then Paranthropus may have gone extinct after 1.0 Ma, and possibly as late as 800 ka. ESR dates for Kromdraai A suggest an age of around 1.6 to 2.0 Ma, which is consistent with faunal estimates for this site (Vrba, 1985a; Delson, 1984, 1988). A ‘blind’ ESR dating study of the Gladysvale cave site provides an internally consistent chronology, suggesting an age range of around 320 ka to 2.2 Ma. Considerable support has been found in this study for the inclusion of fossils previously assigned to the taxon A. africanus to Homo. This has a number of important implications for contemporary views of hominid evolution, including a Southern African origin for genus Homo, an origin of Homo greater than 3.0 Ma, and invalidity of genus Australopithecus. Early Homo from southern Africa appears to be very distinct from taxa sampled in East Africa during the same time period. The southern African sample appears to be taxonomically heterogenous, containing separate Homo taxa at Sterkfontein and Swartkrans. It also appears to contain the ancestor of H. habilis, Homo aff. H. habilis, a taxon which includes SK 847 and SK 15 from Swartkrans. The Sterkfontein Homo remains Stw 53 are herein assigned to Homo sp. nov., and possess a morphology consistent with ancestral status to Homo aff. H. habilis. The bearing of southern Africa on questions of fundamental importance to contemporary palaeoanthropology is immense. The results of this study suggest Homo first appeared in this region; that it provided the ancestor of H habilis from Olduvai Gorge, a species which appears to be the ancestor of H. ergaster and H. erectus\ and it documents the survival of australopithecines well into the Middle Pleistocene. Many important questions about the origins and subsequent diversification of Homo, the human genus, and our australopithecine cousins, may ultimately be resolved in southern Africa. Show more