Sterkfontein Formation Research Articles

Endostructural assessment of a hominin maxillary molar (StW 669) from Milner Hall, Sterkfontein, South Africa

The site of the Sterkfontein Caves, South Africa, is one of the richest early hominin fossil-bearing sites in Africa. Recent excavations in the Milner Hall locality have contributed to the discovery of new hominin specimens, including StW 669, a right permanent maxillary first molar (M1). StW 669 was excavated from the T1 deposits, which consist of a mixture of sediments from Members 2 and 5 of the Sterkfontein Formation. Accordingly, the deposits have the potential to contain remains of Australopithecus, Paranthropus and Homo. In this study, we employed micro-focus X-ray tomography in order to assess dental tissue proportions, enamel thickness distribution and enamel-dentine junction morphology as approaches to investigate the taxonomy of StW 669. We compare our results to those generated on the teeth of Australopithecus africanus, Paranthropus robustus, Homo erectus, Homo antecessor, Homo neanderthalensis and Homo sapiens. Our results suggest that StW 669 shares quantitative and qualitative affinities with M1s of Homo in terms of tissue proportions (i.e. two- and three-dimensional average and relative enamel thickness of 1.2–1.3 mm and 18.4, respectively) and enamel thickness distribution (i.e. thickest enamel on the lingual aspect of the protocone). However, data on the enamel-dentine junction morphology of StW 669 are inconclusive as to the tooth’s taxonomic affinities. Pending additional morphometric analyses, our studies of inner morphology of the crown of StW 669 support its attribution to Homo.
 Significance:
 
 The Sterkfontein Caves have contributed significantly to our understanding of early human evolution and continue to do so. This study highlights the specific value of the Milner Hall locality as a valuable store of hominin fossils. Moreover, we tentatively clarify the enigmatic taxonomic status of StW 669, a right permanent maxillary first molar, excavated from the T1 deposit of Milner Hall. Pending additional morphometric evidence, our preliminary data on tissue proportions, enamel thickness distribution and enamel-dentine junction morphology, suggest an attribution of StW 669 to early Homo. This result is significant given the historical contention concerning the presence of early Homo at Sterkfontein.

Hominin cranial fragments from Milner Hall, Sterkfontein, South Africa

The Sterkfontein Caves site is one of the richest early hominin localities in Africa. In addition to significant fossil assemblages from Members 2 and 4 of the Sterkfontein Formation, recent excavations have revealed hominin-bearing sedimentary deposits in the lesser-known Milner Hall. We describe two hominin cranial fragments excavated from the Milner Hall in 2015 and present the results of a high-resolution microtomographic-based approach to diagnosing the anatomical and taxonomical origin of these specimens. Based on external morphology, StW 671 and StW 672 are tentatively identified as frontal and occipital fragments, respectively. Our non-invasive bi-dimensional quantitative investigation of the two cranial fragments reveals a mean cranial thickness of 8.8 mm and 5.6 mm for StW 671 and StW 672 respectively and a contribution of the diploic layer to the cumulative cranial thickness that is less than 50%. While the mean cranial thickness of StW 671 falls within the range of Homo, the relative proportion of the diploë in both StW 671 and StW 672 is lower than in Australopithecus (>60%) and extant humans (>50%). Accordingly, in terms of both cranial thickness and inner structural organization, the Milner Hall hominins combine derived and unique traits, consistent with the condition of other postcranial and dental material already described from the deposit. Moreover, our study opens interesting perspectives in terms of analysis of isolated cranial fragments, which are abundant in the hominin fossil record.
 Significance:
 
 The Sterkfontein Caves have widely contributed to our understanding of human evolution.
 Besides the well-known Members 4 and 2, where the iconic ‘Mrs Ples’ and ‘Little Foot’ have been found, in this study we suggest that the Milner Hall locality represents an additional, stratigraphically associated source of not only fossil hominins, but also Oldowan stone tools.
 In particular, we describe for the first time two cranial fragments, StW 671 and StW 672, identified as frontal and occipital bones, respectively.
 Our microtomographic-based analysis of these materials reveals some affinities with Homo combined with unique characters.
 In this context, our study suggests an intriguing mosaicism consistent with the description of the two fossil hominins found in the Milner Hall.

Hominin hand bone fossils from Sterkfontein Caves, South Africa (1998–2003 excavations)

We describe eleven hominin metacarpals and phalanges recovered from Jacovec Cavern and Member 4 of the Sterkfontein Formation between 1998 and 2003. Collectively, the fossils date in excess of 2.0 Ma, and are probably attributable to Australopithecus africanus and/or Australopithecus prometheus. When combined with results of previous studies on Australopithecus postcranial functional morphology, the new data presented here suggest that at least some late Pliocene and/or early Pleistocene hominins from Sterkfontein were arboreally adept. This finding accords with the reconstruction of the site's >2.0 Ma catchment area as well-vegetated and containing significant woody components. In addition, most of the new specimens described here evince morphologies that indicate the hands from which they derived lacked complete modern humanlike manual dexterity, which is integral to the manufacture and use of intentionally shaped stone tools. The absence of lithic artifacts from both stratigraphic units from which the fossils were excavated is consistent with this conclusion.

The stratigraphy and formation history of fossil- and artefact-bearing sediments in the Milner Hall, Sterkfontein Cave, South Africa: New interpretations and implications for palaeoanthropology and archaeology

The Sterkfontein palaeokarst deposits, the richest repository of Australopithecus fossils in the world, are currently divided into six members (M1–M6) and named the Sterkfontein Formation (Partridge and Watt, 1991). In this system, it was proposed that the passages and chambers deeper than the Silberberg Grotto formed most recently and are filled with comparatively young sediments from newer openings or reworked sediments from older, upper chambers. Here we describe the geomorphology, sedimentology, fauna and archaeological evidence from six deposits excavated near the base of the system in the Milner Hall. The use of a multidisciplinary approach enabled us to clarify the complex stratigraphic history, to track artefact-bearing deposits through multiple phases of deposition, and to identify an early deposit accumulated from the Silberberg Grotto to the base of the system. We propose that the Australopithecus-bearing Member 2 deposit originally extended down to near the base of the Milner Hall. We further propose that the vertical extent of the cave system was developed prior to the opening to the landscape surface, and that at that time the groundwater level was comparable to that seen now. We therefore argue that some of the earliest palaeoanthropological material in South Africa may have been deposited into the deepest chambers of the Sterkfontein Caves.

Early hominid dental remains from Members 4 and 5 of the Sterkfontein Formation (1966–1996 excavations): Catalogue, individual associations, morphological descriptions and initial metrical analysis

The fossils recovered from the Sterkfontein Formation represent, without doubt, the largest collection of early hominid specimens from a single locality. Among the over 600 entries in the catalogue of fossil hominid specimens recovered since 1966, there are 242 dental remains (isolated teeth, jaws with two or more teeth, isolated teeth in association) for a total number of 495 teeth. The aim of this paper is to provide morphological descriptions of all hominid dental specimens recovered between 1968 and 1996 from areas presently known as Members 4 and 5 of the Sterkfontein site. Together with the descriptions, explanatory catalogue information is provided, along with basic measurements and summary statistics. This paper consists of six sections, with descriptive tables: (1) Catalogue of dental remains, arranged numerically. This includes isolated teeth, specimens with teeth still in position within their jaws, and specimens comprised of isolated teeth in association. (2) List of specimens with more complete dentition and the numbers of available teeth per tooth class. (3) List of specimens subdivided in tooth class, with an indication of their preservation, of the wear, if any, and with measurements (mesiodistal and buccolingual diameters) of the individual teeth. (4) List of associations of isolated teeth as individuals i.e. dental remains that can be associated with one another. Some remarks on the relative abundance of maxillary versus mandibular teeth, and on the numbers of available teeth are presented. (5) Morphological descriptions. (6) Summary statistics for the entire Sterkfontein sample (thus including specimens recovered both before and after 1966) and updated descriptive statistics for South African early hominids ( A. africanus, A. robustus, South African early Homo). We have compared the coefficients of variation for the MD and BL diameters of the permanent teeth of the Sterkfontein Member 4 hypodigm of A. africanus with the hypodigms of the early hominid taxa. The results show that the Sterkfontein Member 4 sample is not consistently more variable than the other fossil hominid samples analysed; it turned out to be generally less variable than H. habilis sensu lato and A. boisei; it shows overall similar levels of variability to A. afarensis and higher levels than A. robustus. These results, per se, do not provide evidence of the existence of multiple species in the Sterkfontein Member 4 sample.

Description, new reconstruction, comparative anatomy, and classification of the Sterkfontein Stw 53 cranium, with discussions about the taxonomy of other southern African early Homo remains

Specimen Stw 53 was recovered in 1976 from Member 5 of the Sterkfontein Formation. Since its incomplete initial description and comparison, the partial cranium has figured prominently in discussions about the systematics of early Homo. Despite publication of a preliminary reconstruction in 1985, Stw 53 has yet to be compared comprehensively to other Plio-Pleistocene fossils or assessed systematically. In this paper, we report on a new reconstruction of this specimen and provide a detailed description and comparison of its morphology. Our reconstruction differs in important respects from the earlier one, especially in terms of neurocranial length, breadth, and height. However, given that Stw 53 exhibits extensive damage, these dimensions are most likely prone to much error in reconstruction. In areas of well-preserved bone, Stw 53 shares many cranial features with Homo habilis, and we propose retaining it within this species. We also consider the affinities of dental remains from Sterkfontein Member 5, along with those from Swartkrans and Drimolen previously assigned to Homo. We find evidence for sympatry of H. habilis and Australopithecus robustus and possibly Plio-Pleistocene Homo sapiens sensu lato in Sterkfontein Member 5. At Swartkrans and Drimolen, we find evidence of H. habilis. We also compare the morphologies of Stw 53 and SK 847 and find compelling evidence to assign the latter specimen to H. habilis, as has been proposed.

Contribution to the speleology of Sterkfontein Cave, Gauteng Province, South Africa

The authors present more data about the speleological aspect of the Sterkfontein Cave, famous for its bone breccia which yielded abundant hominid remains. They also briefly review the previous voluminous studies by numerous authors, which are mainly dealing with the paleontology, stratigraphy and sedimentology of the breccia. The present investigations were oriented to hitherto poorly investigated aspects such as detail mapping of the cave, its country rock stratigraphy and recording the underground extension of the basal part of the breccia body. The cave consists of a complex network of phreatic channels, developed along joints in Neoarchaean cherty dolostone over a restricted surface of 250x250m. The combined length of all passages within this area amounts to 5,23km. The system extends over a height of about 50m and the dry part of it is limited downwards by the water-table appearing as numerous static pools. The fossiliferous breccia (= Sterkfontein Formation) forms an irregular lenticular mass 75x25m horizontally by 40m vertically, which is included within the passage network. It crops out at surface and in the cave, and resulted from the filling of a collapse chamber, which was de-roofed by erosion. The present investigation confirmed that the cave and the Sterkfontein Formation are part of a single speleogenetic event. The breccia resulted from cavity filling by sediments introduced from a pit entrance, whereas many of the phreatic passages around it, which are developed at the same elevation, were only partly filled or remained entirely open up to present. This filling took place mainly in a vadose environment. Taking into account the age of the Sterkfontein Formation (>3,3-1,5 My, from base to top), the geomorphic evolution of the landscape and the context of other caves in the region, it seems that the cave might have started to form 5 My ago. It has been continuously developing up to present as a result of a slow drop of the water-table.

Morphology and affinities of new hominin cranial remains from Member 4 of the Sterkfontein Formation, Gauteng Province, South Africa

Descriptions are provided of 27 hominin cranial specimens recovered from Member 4 of the Sterkfontein Formation between 1968 and 1994. Provisional statements of taxonomic affinity are given. The principal conclusion of this overview is that the bulk of the cranial remains from Member 4 are attributable to Australopithecus africanus or are consistent with the anatomy of that species, while some others are indeterminate. No specimen can be assigned confidently to a known species other than A. africanus. However, two specimens document the possibility that a second, possibly new species is represented among the Member 4 hominins, although such a species is difficult to characterize on cranial evidence alone.

The mixed dentition and associated skull fragments of a juvenile fossil hominid from Sterkfontein, South Africa.

In April-May 1983, the late A.R. Hughes and his field team recovered more than 40 bone fragments and teeth from a single solution pocket of the Sterkfontein Formation. After preparation and reconstruction by JMC, it was recognised that these fragments represent a single juvenile individual (Stw 151), consisting of more than 40 cranial and dental parts, with mixed dentition. It constitutes the most complete set of jaws and teeth of an early hominid child since the Taung child was recovered in 1924. In this paper, the morphological and metrical features of the individual teeth are described. The other associated skull fragments (right ramus of the mandible, left petrous bone, right glenoid region) are also described. Comparisons are made with other South (and East) African fossil hominids. The beautiful preservation simultaneously of most of the deciduous teeth and of the permanent teeth exposed in their crypts allows an accurate analysis of the developmental sequence. A report on the dental developmental status of this juvenile is presented. On the basis of the microanatomical study of the developing permanent teeth, the estimated age at death is 5.2-5.3 years. Reconstructions of the maxillary and mandibular arcades are also offered. The morphological and metrical features of Stw 151 raise the possibility that it may represent a hominid more derived towards an early Homo condition than the rest of the A. africanus sample from Member 4.

The mixed dentition and associated skull fragments of a juvenile fossil hominid from Sterkfontein, South Africa

In April–May 1983, the late A.R. Hughes and his field team recovered more than 40 bone fragments and teeth from a single solution pocket of the Sterkfontein Formation. After preparation and reconstruction by JMC, it was recognised that these fragments represent a single juvenile individual (Stw 151), consisting of more than 40 cranial and dental parts, with mixed dentition. It constitutes the most complete set of jaws and teeth of an early hominid child since the Taung child was recovered in 1924. In this paper, the morphological and metrical features of the individual teeth are described. The other associated skull fragments (right ramus of the mandible, left petrous bone, right glenoid region) are also described. Comparisons are made with other South (and East) African fossil hominids. The beautiful preservation simultaneously of most of the deciduous teeth and of the permanent teeth exposed in their crypts allows an accurate analysis of the developmental sequence. A report on the dental developmental status of this juvenile is presented. On the basis of the microanatomical study of the developing permanent teeth, the estimated age at death is 5.2–5.3 years. Reconstructions of the maxillary and mandibular arcades are also offered. The morphological and metrical features of Stw 151 raise the possibility that it may represent a hominid more derived towards an early Homo condition than the rest of the A. africanus sample from Member 4. Am J Phys Anthropol 106:425–465, 1998. © 1998 Wiley-Liss, Inc.

Geomorphic perspectives on the sterkfontein australopithecine breccias

Breccias in the upper Sterkfontein cave system levels have yielded artifact assemblages as well as Homo and Australopithecus africanus remains. As mapped by the author, this sytem can be subdivided into a northern sector, comprising small, bedding-controlled passageways, and a southern one with large galleries controlled by subvertical fracture zones and partly filled with two generations of external, detrital sediment. A four-stage model describes the development of these deposits. The implications of this study include: (1) The caves formed in one rather than two phases, as a result of structural rather than watertable controls. (2) The lowest strata of both depositional generations, 50–60 m below the hillcrest are probably the oldest. T. C. Partridge's Sterkfontein Formation only includes approximately the upper half of the stratigraphic column recognized here. Deposits underlying those he described are also fossiliferous and probably substantially older than the 2·8+ million year age attributed to the lower units of the Sterkfontein Formation. (3) The Sterkfontein Formation, as defined by Partridge, is a composite stratotype, comprising one surface exposure and another underground, at mid to upper levels in the system. Their stratigraphic relationships are obscure and since the lower boundary of the Formation also is in doubt, erection of a formal stratotype is premature. Deep-lying breccias may ultimately warrant another component, extending the Sterkfontein Formation to the lowest known levels of the cave system.

Re-appraisal of lithostratigraphy of Sterkfontein hominid site

A new lithostratigraphic classification is proposed for the Sterkfontein hominid site. The Sterkfontein Formation is defined in terms of constituent members and beds. The new terminology is correlated with that used previously and, where possible, hominid finds are linked to the newly defined lithostratigraphic units.

A fossil skull probably of the genus Homo from Sterkfontein, Transvaal

A skull with numerous Homo features was discovered at Sterkfontein, near Krugersdorp, Transvaal, in August 1976. It stems from member 5 of the Sterkfontein Formation, with stone tools and with fauna pointing to an age of 2.0-1.5 Myr. The underlying member 4 contains Australopithecus africanus, no stone tools, and fauna dated 3.0-2.5 Myr. The new find supports the view that the Sterkfontein toolmaker was not the earlier A. africanus, but a later hominid related to Homo habilis. By a remarkable double coincidence, the first pieces of the new skull, Stw 53, were found on August 9, 1976, 40 years to the day after Robert Broom's first visit to Sterkfontein, while the last part came to light on August 17, the 40th anniversary of Broom's first discovery of a hominid cranium at Sterkfontein. Although most of the fragments were found in a decalcified pocket of cave earth, one large part of the calvaria was still present in the calcified wall of the pocket, thus establishing indisputably the provenance of the specimen.