Volume 23 1980
Permanent URI for this collectionhttps://wiredspace.wits.ac.za/handle/10539/15926
Browse
Search Results
Item Palaeontologia africana Volume 23(Bernard Price Institute for Palaeontological Research, 1980)Item The Sterkfontein Valley australopithecine succession(Bernard Price Institute for Palaeontological Research, 1980) Vrba, E. S.If we knew the kinds and relative frequencies of animal species belonging to a natural living community, we would be able to predict the supporting environment with some accuracy. Unfortunately for the palaeoecologist the equivalent parameters of a fossil assemblage usually differ substantially from those of the ancient living parent community. This distortion results from the action of a number of taphonomic factors during the passage of remains "from the biosphere to the lithosphere". The major steps of palaeoenvironmental reconstruction from fossils follow a circuitous route of erecting hypotheses upon hypotheses: 1. Analyses of taxonomy and relative frequency. 2. Recognition of environmental indicators (El): Which fossil groups are environmentally specialized (i.e. good Els); and precisely what kind of environments do they indicate? (estimated from modern analogy). 3. Recognition of taphonomic biases: Have the proportions of Els in the original community been distorted by preferential inclusion and survival in the assemblage? Such bias or distortion may be caused by many factors, for example seasonality and duration of deposition, geographic area sampled, mode of death, transport and accumulation, species death rate, and so forth. 4. Estimation of El proportions in the original community by correcting where necessary for taphonomic biases. 5. Interpretation of taxonomic and morphologic change: Let us assume that estimates of original EI proportions, resulting from steps 1-4, can be seen to change significantly in chronologically successive strata in one area like the Sterkfontein Valley. Must such morphologic/ taxonomic change necessarily imply a change in the ecosystem, or may it imply no more than the passage of time? A particular palaeoenvironmental study on fossil assemblages from Sterkfontein, Swartkrans and Kromdraai is followed through steps 1-5 to its conclusion.Item "Australopithecus afarensis" and A. Africanus: Critique and an alternative hypothesis(Bernard Price Institute for Palaeontological Research, 1980) Tobias, Phillip V.During the seventies, a succession of East African discoveries has been claimed to represent the "true" ancestral line of modern man, thus relegating A. africanus, and especially its Transvaal subspecies, to a subordinate role in hominid phylogeny. The latest such attempt has been the claim of Johanson and his co-workers that the 3, 7-2,6 My-old hominids of Laetoli in Tanzania and of Hadar in Ethiopia represent a new species, "A. afarensis", which led to H. habilis, whilst A. africanus represents early stages in a specialized side-branch leading to A. robustus and A. boisei. A critique of the diagnostic criteria of "A. afarensis" reveals that on the available evidence, the Laetoli and Hadar fossils cannot be distinguished at specific level from A. africanus transvaalensis. Furthermore, it is by no means clear that the pooling for statistical and comparative purposes of the Hadar and Laetoli fossils is justified. Hominids from the two sites are separated by about 800 000 years and about 1 600 km as well as by morphometric differences. As an alternative hypothesis, it is proposed that the Laetoli and Hadar hominids belong to the same lineage as that represented by the hominids of Makapansgat Members 3 and 4 and of Sterkfontein Member 4. Moreover, it is hypothesized that the Laetoli and Hadar hominids cannot be separated morphologically from A. africanus and that they represent two new subspecies of that species. Since "A. afarensis" is tied to a Laetoli specimen as holotype, only the Laetoli specimens should be designated A. africanus afarensis (though A. africanus tanzaniensis suggested by the author in 1978 would have been a more appropriate nomen) and the Hadar fossils A. africanus aethiopicus. These newest East African discoveries afford strong confirmation of the hypothesis that A. africanus is the common ancestor of the two later hominid lineages, A. robustuslboisei and Homo, leading from H. habilis through H. erectus to H. sapiens.Item On the genesis of bipedalism(Bernard Price Institute for Palaeontological Research, 1980) Suzman, Ivan M.Bipedalism is the hallmark of the Hominidae, past and present. Only against this fundamental adaptive background could cerebral, dental and manual modifications develop to change ape into ape-man, and ape-man into man. Yet surprisingly little is known of its origin, of the variety of forms of locomotor behaviour it has encompassed, or about the sequence of postural refinements which has led to our modern pattern of stance and gait. In an attempt to trace the Plio-Pleistocene history of two-footedness, lower limb fossils of early hominids are examined here. South and East African sites are covered, with special reference to the period 3,6 to 1 ,5 My ago. Numerous structural challenges had to be met so that uprightness could evolve successfully. Several are considered of special interest here, including sacroiliac joint consolidation, a lumbo-acetabular weight transfer mechanism, acetabular remodelling and femorotibial alignment. These features have contributed to the attainment of balance over two limbs, minimal eccentric joint movements and a flow of body weight close to or through joint centres. A primary palaeoanthropological question is then discussed: the time period during which cladogenesis brought about the emergence of earliest Homo from an Australopithecus stock. Lower limb evidence is used to evaluate whether A. africanus postdated this split, and in so doing the possibility is considered that southern African australopithecines exhibited parallel evolution to Homo, rather than having been ancestral. Finally, comparisons are drawn between certain East and South African features of pelvic and lower limb evolution. A chronology of osseous aspects of such evolution is proposed.Item Models in geomorphology- Quaternary evolution of the actual relief pattern of coastal central and northern Namib desert(Bernard Price Institute for Palaeontological Research, 1980) Rust, U.Field and laboratory results gained at various SWA/Namibian sites between the Kuiseb river in the south and the Unjab river in the north are presented. At the Namib coast under study two low stands of sea level and two high stands, one of them of Intra-Wurmian age, can be proved. From Toscanini northward a third (? Holocene) high stand exists besides the other two. The former shore lines can be linked spatially and temporally to the terrestrial relief sequences by means of fluvial and eolian land forms and sediments. Thus the changing patterns of more arid or more humid environments at different morphoclimatic stages up to the present one can be described. Furthermore, it is evident that the geomorphic processes themselves change regionally, and it is seen that the Central Namib desert is a geomorphologically unique area in comparison with the Skeleton Coast and the southern dune area. Finally, the tendencies of Quaternary landscape evolution even enable us to deduce some geoecological consequences concerning man's activities in this desert.Item Late Pleistocene and Holocene climates as viewed from Verlore Vlei(Bernard Price Institute for Palaeontological Research, 1980) Parkington, JohnEvidence from a number of sites along the lower reaches of the Verlore Vlei and the adjacent coastline is interpreted as reflecting considerable environmental change since about 18 000 B.P. In particular seven points are relevant.Item An overview of palaeomagnetic chronology with special reference to the South African hominid sites(Bernard Price Institute for Palaeontological Research, 1980) McFadden, P. L.The phenomena of secular variation, polarity reversals and apparent polar wander are discussed. The calibration of each of these phenomena for use in palaeomagnetic chronology is outlined and the use of each of these calibrated scales for dating is briefly explained. A successful application of the polarity reversal dating technique is presented as an example of the potential for palaeomagnetic chronology in South Africa. In this example it is shown that the age of the important Member 3 in Makapan is about 3 My. It is concluded that palaeomagnetic chronology has a vast potential in South Africa ; a palaeomagnetic laboratory specifically oriented to chronological problems would be extremely valuable.Item Dune systems an palaeoenvironments in southern Africa(Bernard Price Institute for Palaeontological Research, 1980) Lancaster, N.Extensive systems of fixed linear dunes occur throughout the Kalahari. Together the dunes form a semicircular arc with a radius of 1 000 km which corresponds approximately with the pattern of outblowing winds around the South African anticyclone. The dunes were formed by a wind regime broadly similar to that existing today. However, differences between dune alignments and present-day potential resultant sand flows in the northern part of the system suggest that shifts in the position and strength of the South African anticyclone may have taken place since these dunes were formed. Comparison of the extent of fixed dunes with that of the presently active dunes indicates that the extent of the arid zone in southern Africa has altered substantially in the past. Evidence exists for at least two periods of much greater aridity in the subcontinent, but their dating remains uncertain.Item Last integral shorelines in the South Cape(Bernard Price Institute for Palaeontological Research, 1980) Davies, OliverMy paper discusses the Last Interglacial shorelines of the South Cape with reference to findings from the rest of the world. I call them Eemian shorelines, and define Eem as an interglacial with three peaks of sea level separated by two stadials when the ocean dropped. I use the term Eem though it has been wrongly applied in north-west Europe (Kukla 1977). Other names have been given to this interglacial; in the deep-ocean record the stage is referred to as Stage X or Stage 5. It has been dated mostly by Uranium/Thorium as lasting from about 125 000 to 80 000 B.P. The dates and the fluctuations will be discussed belowItem The nature and genesis of solution cavities (Makondos) in Transvaal Cave breccias(Bernard Price Institute for Palaeontological Research, 1980) Brink, A. B. A.; Partridge, T. C.The discovery of a large part of the cranium of a hominid, evidently closely related to Homo habilis (Hughes and Tobias 1977) in a solution cavity within the calcified Member 5 of the Sterkfontein Formation (Partridge 1978) has again drawn attention to the frequent occurrence of these features in the hominid-bearing breccias of the Transvaal. The authors first studied these features at Makapansgat (fig. 1) some fifteen years ago and have since then become aware of their very widespread occurrence in soluble rocks in many parts of the world. All subsequent information has served to confirm the origin of these features, but, since these were never published, it is worthwhile to place these findings on record. Solution cavities, or Makondos, in the Transvaal cave breccias are soil-filled pits shaped like an inverted cone. Their walls and intervening areas of the calcified cave deposit are usually rough, and the coalescing of adjacent cavities below the surface is common. They seldom exceed 2 m in diameter and 6 m in depth and occur at intervals of 2 to 3 m in the calcified cave deposit.