Taxonomic status of the hominine cranium KNM-ER 1813 (primates: Homininae) from the Plio/Pleistocene of Koobi Fora

The hominine cranium KNM-ER 1813, from the late Plio/Pleistocene of Koobi Fora, has been regarded recently by some authors as a female ofHomo habilis Leakey, Tobias, andNapier, 1964 and by others as an enigma. Reassessment of its cranial morphology, dental metrics, proportions, and a new detailed determination of its sex indicates that it does not conform with the diagnosis forH. habilis, and is probably a male. It is sympatric withH. habilis yet shows more primitive features and rather a closer affinity to the smaller, more primitive chronospeciesH. antiquus Ferguson, 1984, and is thus the first, nearly complete skull of our oldest known human ancestor.     

Re-appraisal of the stratigraphy and determination of new U-Pb dates for the Sterkfontein hominin site, South Africa

Sterkfontein Caves is the single richest early hominin site in the world with deposits yielding one or more species of Australopithecus and possible early Homo, as well as an extensive faunal collection. The inability to date the southern African cave sites accurately or precisely has hindered attempts to integrate the hominin fossil evidence into pan-African scenarios about human evolutionary history, and especially hominin biogeography. We have used U-Pb and U-Th techniques to date sheets of calcium carbonate flowstone inter-bedded between the fossiliferous sediments. For the first time, absolute age ranges can be assigned to the fossil-bearing deposits: Member 2 is between 2.8 ± 0.28 and 2.6 ± 0.30 Ma and Member 4 between 2.65 ± 0.30 and 2.01 ± 0.05 Ma. The age of 2.01 ± 0.05 Ma for the top of Member 4 constrains the last appearance of Australopithecus africanus to 2 Ma. In the Silberberg Grotto we have reproduced the U-Pb age of ∼2.2 Ma of for the flowstones associated with StW573. We believe that these deposits, including the fossil and the flowstones, accumulated rapidly around 2.2 Ma. The stratigraphy of the site is complex as sediments are exposed both in the underground chambers and at surface. We present a new interpretation of the stratigraphy based on surface mapping, boreholes logs and U-Pb ages. Every effort was made to retain the Member system, however, only Members 2 and 4 are recognized in the boreholes. We propose that the deposits formally known as Member 3 are in fact the distal equivalents of Member 4. The sediments of Members 2 and 4 consisted of cone-like deposits and probably never filled up the cave. The U-Th ages show that there are substantial deposits younger than 400 ka in the underground cave, underlying the older deposits, highlighting again that these cave fills are not simple layer-cakes.     

A large male hominin cranium from Sterkfontein, South Africa, and the status ofAustralopithecus africanus

Stw 505 is the most complete hominin cranium discovered in Sterkfontein Member 4 since Broom's excavations. It was found in situ in Member 4 breccia in 1989 and is larger, on the whole, than any other cranium from Sterkfontein that has comparable parts. Displacement due to breakage, as well as plastic deformation, has affected Stw 505 in several areas, especially the face and the vault. Diagnosticmorphology is nevertheless abundant in the specimen. In several areas-the distinct anterior pillar, the straight inferior border of the zygoma, the pattern of cresting on the naso-alveolar clivus, the basal aspect of the temporal bone-Stw 505 closely matches the morphology of specimens of Australopithecus africanus and is distinct from other hominins. Some isolated characters overlap with other groups, mainly early Homo and/or A. robustus. However, only the hypodigm of A. africanus can accommodate the entire suite of morphology.In some cases, Stw 505 introduces more variation into the Sterkfontein sample. For example, prominent superciliary eminences occupy the medial portions of the supraorbital region and flow medially into a strongly protruding glabellar mound. These characteristics are probably attributable to sexual dimorphism. In many respects, Stw 505 highlights similarities between A. africanus and early Homo. Comparison with other species suggests that males of A. africanus do not show derived features of A. robustus that are not also present in females, and that cranial differences between A. afarensis and A. africanus have, if anything, been understated.     

A new species of the genusAustralopithecus (primates: hominidae) from Plio/Pleistocene deposits west of Lake Turkana in Kenya

The cranium of a robust australopithecine, KNM WT 17000, was discovered from the Plio/Pleistocene deposits west of Lake Turkana in Kenya, and assigned to the speciesAustralopithecus boisei Leakey, 1959. A comparative morphological study shows that it does not conform with the diagnosis forA. boisei. It is characterized by having a much smaller brain, a low hyperprognathous facial skeleton, and a less developed masticatory apparatus. Its unique morphological pattern justifies its placement in a new taxon which is calledAustralopithecus walkeri n. sp.     

Craniofacial diversity in earlyHomo and the affinities of the Sterkfontein Valley

The Sterkfontein Valley specimens SK 847 (Swartkrans Member 1) and Stw 53 (Sterkfontein Member 5) provide important evidence of earlyHomo in southern Africa. However, specific identity has been disputed, with that of SK 847 especially contentious. Opinions differ markedly as to whether the specimens are conspecific or not, whether they should be referred to East African earlyHomo species, or whether they represent new species. Morphometric analysis of facial dimensions reveals contrasting affinities for the two South African fossils, and so does not support claims for their conspecifity. Stw 53 is very like smaller East African crania referred toH. habilis, whereas SK 847 has a distinctive facial pattern. In some respects it resembles early AfricanH. erectus (=H. ergaster), but with a markedly more projecting mid-face, prominent zygomatic and unexpanded frontal region, all of which militate against inclusion in that species. The taxonomic implications of these contrasting facial affinities are briefly discussed.     

Stratigraphy, artefact industries and hominid associations for Sterkfontein, member 5

A revised stratigraphy for the early hominid site of Sterkfontein (Gauteng Province, South Africa) reveals a complex distribution of infills in the main excavation area between 2.8 and 1.4 m.y.a, as well as deposits dating to the mid to late Pleistocene. New research now shows that the Member 4 australopithecine breccia (2.8-2.6 Ma) extends further west than was previously thought, while a late phase of Member 4 is recognized in a southern area. The artefact-bearing breccias were defined sedimentologically as Member 5, but one supposed part of these younger breccias, the StW 53 infill, lacks in situ stone tools, although it does appear to post-date 2.6 Ma when artefacts first appear in the archaeological record. The StW 53 hominid, previously referred to Homo habilis, is here argued to be Australopithecus. The first artefact-bearing breccia of Member 5 is the Oldowan Infill, estimated at 2-1.7 Ma. It occupies a restricted distribution in Member 5 east and contains an expedient, flake-based tool industry associated with a few fossils of Paranthropos robustus. An enlarged cave opening subsequently admitted one or more Early Acheulean infills associated in Member 5 west with Homo ergaster. The artefacts attest to a larger site accumulation between ca. 1.7 and 1.4 Ma, with more intensive use of quartzite over quartz and a subtle but important shift to large flakes and heavier-duty tools. The available information on palaeoenvironments is summarized, showing an overall change from tropical to sub-tropical gallery forest, forest fringe and woodland conditions in Member 4 to more open woodland and grassland habitats in the later units, but with suggestions of a wet localized topography in the Paranthropus -bearing Oldowan Infill.     

The view from the Lincoln Cave: mid- to late Pleistocene fossil deposits from Sterkfontein hominid site, South Africa

The Lincoln-Fault cave system lies adjacent to the Sterkfontein Cave system in the Cradle of Humankind World Heritage Site, Gauteng Province, South Africa. Lincoln Cave contains a mid- to late Pleistocene fossiliferous deposit which has been dated using uranium series methods to between 252,600+/-35,600 and 115,300+/-7,700 years old. Although speleologists presumed that there was no connection between the Lincoln Cave and Sterkfontein Cave systems, results of excavations conducted in 1997 suggest a link between the deposits. Detailed comparisons of artifacts, fauna, hominid material, and a statistical correspondence analysis (CA) of the macromammalian fauna in the deposits strongly support this hypothesis. The recovery of Early Acheulean-type artifacts from the Lincoln Cave suggests that older artifacts eroded out of Sterkfontein Member 5 West and were redeposited into the younger Lincoln Cave deposits. The close physical proximity of these deposits, and the nature of the material recovered from them, indicates that the material was probably redeposited via a link between the two cave systems. Although faunal mixing is present, it is possible to say that large carnivorans become more scarce at Sterkfontein during the mid- to late Pleistocene, while small canids and felids appear to become more abundant, indicating that large and small carnivorans probably varied their use of the site through time. This may also reflect an increasing presence of humans in the Sterkfontein area during the mid- to late Pleistocene.     

Revision of the subspecies ofAustralopithecus africanus (primates: Hominidae), including a new subspecies from the late pliocene of Ethiopia

The subspecies ofAustralopithecus africanus Dart, 1925 have been revised in a morphological and statistical analysis. Four subspecific names were previously proposed, but only one was found to be valid. The subspeciesA. africanus transvaalensis (Broom, 1936), from the Plio/Pleistocene of South Africa, cannot be sustained due to an insufficient sample, and is combined with the nominate race,A. a. africanus. The type ofA. africanus afarensis Tobias, 1980 is a mistake in identification and notA. africanus, but a pongid. The population ofA. africanus from the late Pliocene of Ethiopia does indeed represent a relatively small-toothed geographical race for which the nameA. africanus aethiopicus was conditionally proposed; and the lectotype for it, A.L. 288-1, is notA. africanus, but the type ofHomo antiquus Ferguson, 1984. The trinominalaethiopicus is thus unavailable for the Ethiopian race, which is redescribed as a new subspecies,A. africanus miodentatus n. ssp., and the mandible A.L. 266-1 is designated as the holotype.     

The context of Stw 573, an early hominid skull and skeleton from Sterkfontein Member 2: taphonomy and paleoenvironment

The reconstructed taphonomic and paleoenvironmental contexts of a ca. 4 million-year-old partial hominid skeleton (Stw 573) from Sterkfontein Member 2 are described through presentation of the results of our analyses of the mammalian faunal assemblage associated stratigraphically with the hominid. The assemblage is dominated by cercopithecoids (Parapapio and Papio) and felids (Panthera pardus, P. leo, Felis caracal, and Felidae indet.), based on number of identified specimens, minimum number of elements and, minimum number of individuals. In addition, the assemblage is characterized by a number of partial skeletons and/or antimeric sets of bones across all taxonomic groups. There is scant indication of carnivore chewing in the assemblage. These observations, in addition to other taphonomic data, suggest that the remains of many animals recovered in Member 2 are from individuals that entered the cave on their own-whether accidentally by falling through avens connecting the cave to the ground surface above or by intentional entry-and were then unable to escape, rather than primarily through systematic collection by a biotic, bone-accumulating agent. The taphonomic conclusion that animals with climbing proclivities (i.e., primates and carnivores) are preferentially preserved over other taxa, ultimately because of those proclivities, urges caution in assessing the fidelity of the assemblage for reconstruction of the Member 2 paleoenvironment. With that caveat, we infer that the Member 2 paleoenvironment was typified by rolling, rock-littered and brush- and scrub-covered hills, indicated by the abundant F. caracal and cercopithecoid fossils recovered and the identified presence of the extinct Caprinae Makapania broomi. In addition, the valley bottom may have retained standing water year-round, perhaps supporting some tree cover--a setting suitable for the well-represented ambush predator P. pardus and suggested by the presence of Alcelaphini. Finally, the reconstructed taphonomic and paleoenvironmental settings of Sterkfontein Member 2 are compared to penecontemporaneous sites in South and East Africa.     

Upper Molar Cusp Dimensions of South African Australopithecines

Recently, a number of articles have been published on the mechanisms of dental development, and in particular on the genetic control of dental formation. As a specific example of the potential of this kind of research for paleoanthropological studies, cusp areas of upper molars of two species of South African Australopithecines (Australopithecus africanus, A. robustus) have been examined. The results suggest notable differences between the two species, possibly related to markedly different developmental pathways that are still far from clear in their details.     

The taxonomic implications of cranial shape variation in Homo erectus

The taxonomic status of Homo erectus sensu lato has been a source of debate since the early 1980s, when a series of publications suggested that the early African fossils may represent a separate species, H. ergaster. To gain further resolution regarding this debate, 3D geometric morphometric data were used to quantify overall shape variation in the cranial vault within H. erectus using a new metric, the sum of squared pairwise Procrustes distances (SSD). Bootstrapping methods were used to compare the H. erectus SSD to a broad range of human and nonhuman primate samples in order to ascertain whether variation in H. erectus most clearly resembles that seen in one or more species. The reference taxa included relevant phylogenetic, ecological, and temporal analogs including humans, apes, and both extant and extinct papionin monkeys. The mean cranial shapes of different temporogeographic subsets of H. erectus fossils were then tested for significance using exact randomization tests and compared to the distances between regional groups of modern humans and subspecies/species of the ape and papionin monkey taxa. To gauge the influence of sexual dimorphism on levels of variation, comparisons were also made between the mean cranial shapes of single-sex samples for the reference taxa. Results indicate that variation in H. erectus is most comparable to single species of papionin monkeys and the genus Pan, which included two species. However, H. erectus encompasses a limited range of variation given its extensive geographic and temporal range, leading to the conclusion that only one species should be recognized. In addition, there are significant differences between the African/Georgian and Asian H. erectus samples, but not between H. ergaster (Georgia+Africa, excluding OH 9 and Daka) and H. erectus sensu stricto. This finding is in line with expectations for intraspecific variation in a long-lived species with a wide, but probably discontinuous, geographic distribution.     

A new species of the genusHomo (primates: Hominidae) from the Plio/Pleistocene of Koobi Fora,in Kenya

Reassessment of the hominine cranium, KNM-ER 1813, from the Plio/Pleistocene of Koobi Fora, in Kenya, shows that it is not a small-brained, extreme female variant ofH. habilis Leakey, Tobias, & Napier, 1964. Its cranial and dental morphology, morphometrics, and proportions do not conform with eitherH. habilis orH. antiquus Ferguson, 1984. On the basis of its distinctive morphological pattern and mensural gaps which distinguish it fromH. habilis andH. antiquus, the cranium KNM-ER 1813 is described as a common variant representing a male of a small-brained, intermediate population linkingH. habilis 1.83 Myr BP withH. antiquus 2.9 Myr BP, and a new paleospecies of the genusHomo. A key to the Homininae is provided and the phylogenetic relationship of KNM-ER 1813 toH. habilis andH. antiquus is discussed. This paper is dedicated to the memory of my wife,Grace, whose assistance will be sorely missed.     

The cation status of some indigenous plants from a Cango valley limestone-sandstone transition,South Africa

Leaf tissue of four representative species from a limestone-sandstone transition, together with their respective soils, were analysed for cations. The species studied comprisedLeucospermum cuneiforme (Proteaceae) from the acid sandstone,Indigofera sp. nov. (Fabaceae) from the base-rich limestone,Elytropappus rhinocerotis (Asteraceae) from the transition zone andDodonaea angustifolia (Sapindaceae) which occured on all three substrates. The sandstone substrate is low in cations, particularly K and it is suggested that the Leucospermum may supplement its K nutrition with Na. Despite growing on soils of differing cation content, Dodonaea maintained a constant leaf cation content over the three substrates.