We announce a new palaeoanthropological locality, the Andrew Phaswana Site (APS), located near the main Swartkrans Cave in the UNESCO Cradle of Humankind World Heritage Site (hereafter ‘The Cradle’) of South Africa. Preliminary analyses of faunal and lithic assemblages from APS reveal its complex formational history, during which geologically older breccia bodies adhering to the roof and walls of the cave eroded and collapsed in large blocks, and were subsequently incorporated into the floor sediments. As such, the mammalian faunal assemblages are mixed temporally, including Pleistocene and Holocene species. On the other hand, cultural materials buried in the floor, such as lithics, ostrich eggshell fragments, ochre and quartz crystals, likely represent an intact assemblage we preliminarily assign to the Later Stone Age (LSA). LSA sites are rare in the Cradle region, and, along with lithic and faunal assemblages from Members 4 and 5, respectively, of the Swartkrans Formation (exposed at the main Swartkrans Cave), APS has the potential to provide perspective on later Pleistocene to Holocene human occupation in this area.

The oldest deposit at the hominin-bearing cave of Swartkrans, South Africa, is the Lower Bank of Member 1, dated to ca. 2.2 million years ago. Excavations of this unit have produced a diverse and extensive mammalian fossil record, including Paranthropus robustus and early Homo fossils, along with numerous Oldowan stone tools. The present study focuses on the taxonomic analysis of the micromammalian fossil assemblage obtained from recent excavations of the Lower Bank, conducted between 2005 and 2010, as part of the Swartkrans Paleoanthropological Research Project. The taxonomic composition of this assemblage is dominated by Mystromys, a rodent indicative of grassland environments. Taphonomic analysis indicates an accumulation of prey by Tyto alba (Barn owl) or a related species. Environments inferred from this evidence reflect an open landscape primarily covered by grassland vegetation, but they also feature components of wooded areas, rocky outcrops, and the proximity of a river. The Swartkrans fossil assemblage is compared with Cooper's D (dated to ca. 1.4 Ma) and a modern coprocoenosis of Bubo africanus (spotted eagle-owl) collected within the Swartkrans cave for taxonomic, taphonomic, and paleoecological perspectives. Contrasting fossil and modern micromammalian data provide a better understanding of accumulation processes and facilitate a diachronic reconstruction of changes in climate and landscape evolution. Issues regarding paleoenvironmental reconstruction methodologies based on micromammals are also discussed. (c) 2024 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Since paleontological work began there in 1948, Swartkrans (South Africa) has yielded hundreds of Early Pleistocene hominin fossils, currently attributed to (in ascending order of quantity) cf. Australopithecus africanus, Homo spp., and Paranthropus robustus. The bulk of that large sample comprises craniodental remains, with (mostly fragmentary) postcranial materials being much less abundant at the site. In that context, our announcement here of the first articulating partial os coxae, nearly complete femur, and complete tibia of a young adult hominin (SWT1/HR-2), excavated from the <2.3 to >1.7-million-year-old Hanging Remnant (Member 1) of the Swartkrans Formation, represents an important addition to the understanding of hominin postural and locomotor behavior in Early Pleistocene South Africa. We provide qualitative and quantitative descriptions and initial functional morphological interpretations of the fossils, based mostly on external bone morphology. Epiphyseal fusion data, element dimensions, the crural index, and live body stature and mass estimates that we provide all indicate that SWT1/HR-2 is one of the smallest known adult hominins in the fossil record. We discuss the paleobiological implications of these findings in relation to our taxonomic diagnosis of SWT1/HR-2 as representing P. robustus.

There has been a long debate about the possibility of multiple contemporaneous species of Australopithecus in both eastern and southern Africa, potentially exhibiting different forms of bipedal locomotion. Here, we describe the previously unreported morphology of the os coxae in the 3.67 Ma Australopithecus prometheus StW 573 from Sterkfontein Member 2, comparing it with variation in ossa coxae in living humans and apes as well as other Plio-Pleistocene hominins. Statistical comparisons indicate that StW 573 and 431 resemble humans in their anteroposteriorly great iliac crest breadth compared with many other early australopiths, whereas Homo ergaster KNM WT 15000 surprisingly also has a relatively anterioposteriorly short iliac crest. StW 573 and StW 431 appear to resemble humans in having a long ischium compared with Sts 14 and KNM WT 15000. A Quadratic Discriminant Function Analysis of morphology compared with other Plio-Pleistocene hominins and a dataset of modern humans and hominoids shows that, while Lovejoy's heuristic model of the Ardipithecus ramidus os coxae falls with Pongo or in an indeterminate group, StW 573 and StW 431 from Sterkfontein Member 4 are consistently classified together with modern humans. Although clearly exhibiting the classic "basin shaped" bipedal pelvis, Sts 14 (also from Sterkfontein), AL 288-1 Australopithecus afarensis, MH2 Australopithecus sediba and KNM-WT 15000 occupy a position more peripheral to modern humans, and in some analyses are assigned to an indeterminate outlying group. Our findings strongly support the existence of two species of Australopithecus at Sterkfontein and the variation we observe in os coxae morphology in early hominins is also likely to reflect multiple forms of bipedality.

The StW 573 skeleton of Australopithecus prometheus from Sterkfontein Member 2 is some 93% complete and thus by far the most complete member of that genus yet found. Firmly dated at 3.67 Ma, it is one of the earliest specimens of its genus. A crucial aspect of interpretation of locomotor behaviour from fossil remains is an understanding of the palaeoenvironment in which the individual lived and the manner in which it would have used it. While the value of this ecomorphological approach is largely accepted, it has not been widely used as a stable framework on which to build evolutionary biomechanical interpretations. Here, we collate the available evidence on StW 573’s anatomy in order, as far as currently possible, to reconstruct what might have been this individual’s realized and potential niche. We explore the concept of a common Australopithecus “bauplan” by comparing the morphology and ecological context of StW 573 to that of paenocontemporaneous australopiths including Australopithecus anamensis and KSD-VP-1/1 Australopithecus afarensis. Each was probably substantially arboreal and woodland-dwelling, relying substantially on arboreal resources. We use a hypothesis-driven approach, tested by: virtual experiments, in the case of extinct species; biomechanical analyses of the locomotor behaviour of living great ape species; and analogical experiments with human subjects. From these, we conclude that the habitual locomotor mode of all australopiths was upright bipedalism, whether on the ground or on branches. Some later australopiths such as Australopithecus sediba undoubtedly became more terrestrial, allowing sacrifice of arboreal stability in favour of manual dexterity. Indeed, modern humans retain arboreal climbing skills but have further sacrificed arboreal effectiveness for enhanced ability to sustain striding terrestrial bipedalism over much greater distances. We compare StW 573’s locomotor adaptations to those of living great apes and protohominins, and agree with those earlier observers who suggest that the common panin-hominin last common ancestor was postcranially more like Gorilla than Pan.

AFFILIATIONS: 1Department of Anthropology, University of North Carolina at Greensboro, Greensboro, NC, USA 2Department of Anthropology, University of Wisconsin-Madison, Madison, WI, USA 3Evolutionary Studies Institute, University of the Witwatersrand, Johannesburg, South Africa 4Gray & Pape, Inc., Providence, RI, USA 5Institute of Evolution in Africa, University of Alcalá de Henares, Madrid, Spain 6Department of Anthropology, Rice University, Houston, TX, USA

The fossiliferous deposits within the lower-lying Jacovec Cavern in the locality of Sterkfontein yielded valuable hominin remains, including the StW 578 specimen. Because StW 578 mainly preserves the calotte, the taxonomic status of this specimen has been a matter of discussion. Within this context, here we employed high-resolution microtomography and a landmark-free registration method to explore taxonomically diagnostic features in the external surface of the StW 578 calotte. Our comparative sample included adult humans and common chimpanzees as well as one Australopithecus africanus specimen (Sts 5). We partially restored the StW 578 calotte digitally and compared it to extant specimens and Sts 5 using a landmark-free registration based on smooth and invertible surface deformation. Our comparative shape analysis reveals morphological differences with extant humans, especially in the frontal bones, and with extant chimpanzees, as well as intriguing specificities in the morphology of the StW 578 parietal bones. Lastly, our study suggests morphological proximity between StW 578 and Sts 5. Given the intimate relationship between the brain and the braincase, as well as the integration of the hominin face and neurocranium, we suggest that cranial vault shape differences between StW 578 and extant humans, if confirmed by further analyses, could be either explained by differences in brain surface morphology or in the face. Besides providing additional information about the morphology of the Jacovec calotte that will be useful in future taxonomic discussion, this study introduces a new protocol for the landmark-free analysis of fossil hominin cranial shape. Significance: We provide further information on the enigmatic fossil specimen StW 578. We introduce a new approach for the morphological study of fossil hominin crania. We highlight morphological similarities between StW 578 and ‘Mrs Ples’.

The StW 573 skeleton of Australopithecus prometheus from Sterkfontein Member 2 is some 93% complete and thus by far the most complete member of that genus yet found. Firmly dated at 3.67 Ma it is one of the earliest of its genus. A crucial aspect of interpretation of locomotor behaviour from fossil remains, is an understanding of the palaeoenvironment in which individuals lived and the manner in which they would have used it. While the value of this ecomorphological approach is largely accepted, it has not been widely used, as a stable framework on which to build evolutionary biomechanical interpretations. Here, we collate the available evidence on StW 573’s anatomy in order to reconstruct what might have been this individual’s realised and potential niche. We explore the concept of a common australopithecus bauplan by comparing the morphology and ecological context of StW 573 to that of paenocontemporaneous australopiths including Au. anamensis and KSD-VP-1/1 Au. afarensis. Each was probably substantially arboreal and woodland-dwelling, relying substantially on arboreal resources. Using an hypothesis-driven approach, tested by virtual experiments, in the case of extinct species, biomechanical analyses of the locomotor behaviour of living great ape species, and analogical experiments with human subjects, we conclude that the habitual locomotor mode of all australopiths was upright bipedalism, whether on the ground or on branches. Some later australopiths such as Au. sediba undoubtedly became more terrestrial, allowing sacrifice of arboreal stability in favour of manual dexterity. Indeed, modern humans retain arboreal climbing skills but have further sacrificed arboreal effectiveness for enhanced ability to sustain striding terrestrial bipedalism over much greater distances. We compare StW573’s locomotor adaptations to those of living great apes and protohominins and agree with those earlier observers who suggest that the common panin-hominin Last Common Ancestor was postcranially more like Gorilla then Pan.

We describe late Pliocene and early Pleistocene hominin fossils from Sterkfontein Caves (South Africa), including two femoral specimens, as well as a partial tibia and a partial fibula. The fossils are likely assignable to Australopithecus africanus and/or Australopithecus prometheus and the morphology of each corroborates previous interpretations of Sterkfontein hominins as at least facultative bipeds. Significance: A recent series of papers by our research team describes the morphology of a hominin skeleton from Sterkfontein Caves (South Africa), nicknamed ‘Little Foot’. Based on its unique skull morphology, R.J. Clarke, the skeleton’s discoverer, places it in the species Australopithecus prometheus, as distinct from the better-known and co-occurring Australopithecus africanus. Here we describe additional hominin thigh and leg fossils from Sterkfontein that, when considered in a comparative context, support the hypothesis that there was significant (probably interspecific) variation in South African hominin postcranial morphology during the late Pliocene and early Pleistocene.