Search

The site of Malapa, South Africa, has produced fossil evidence from multiple individuals of Australopithecus sediba including the partial skeletons designated as MH1 (holotype) and MH2 (paratype). A recent article in this Journal presented the hypothesis that MH1 and MH2 are not one species but instead represent two different genera: Australopithecus and Homo, respectively. Here we briefly evaluate this claim. We review the evidence from across the skeleton that demonstrates that MH1 and MH2 represent a single species, and we highlight other fossil samples that show the same pattern of mandibular ramus variation as observed in MH1 and MH2. The evidence shows that there is no reason to separate MH1 and MH2 into different species or genera based upon mandibular ramus morphology. This case illustrates how misleading small fragments of anatomy can be, why researchers should not use such fragments particularly for species and genus-level diagnoses, and why it is essential to use all available evidence. SIGNIFICANCE: This study shows that the mandibular variation that is present in fossils from Malapa attributed to Australopithecus sediba has parallels in both Australopithecus africanus and in Homo. This helps to demonstrate that mandibular form is not sufficient to provide evidence of species diagnosis, but also that the development and adaptations to diet in Au. sediba were overlapping with those present in other related species of hominins.

New ages for flowstone, sediments and fossil bones from the Dinaledi Chamber are presented. We combined optically stimulated luminescence dating of sediments with U-Th and palaeomagnetic analyses of flowstones to establish that all sediments containing Homo naledi fossils can be allocated to a single stratigraphic entity (sub-unit 3b), interpreted to be deposited between 236 ka and 414 ka. This result has been confirmed independently by dating three H. naledi teeth with combined U-series and electron spin resonance (US-ESR) dating. Two dating scenarios for the fossils were tested by varying the assumed levels of222Rn loss in the encasing sediments: a maximum age scenario provides an average age for the two least altered fossil teeth of 253 +82/-70 ka, whilst a minimum age scenario yields an average age of 200 +70/-61 ka. We consider the maximum age scenario to more closely reflect conditions in the cave, and therefore, the true age of the fossils. By combining the US-ESR maximum age estimate obtained from the teeth, with the U-Th age for the oldest flowstone overlying Homo naledi fossils, we have constrained the depositional age of Homo naledi to a period between 236 ka and 335 ka. These age results demonstrate that a morphologically primitive hominin, Homo naledi, survived into the later parts of the Pleistocene in Africa, and indicate a much younger age for the Homo naledi fossils than have previously been hypothesized based on their morphology.

The original version of this article has been amended to include two additional authors: Rick Hunter and Steven Tucker., PaleoAnthropology, 2021: PaleoAnthropology

The Dinaledi Chamber of the Rising Star cave system has yielded a large assemblage of fossil hominin material, attributed to Homo naledi. The unusual taphonomic and geological situation of the assemblage suggested that the remains may have been deliberately deposited in the chamber. However, the route and mechanism of deposition of the remains within the Dinaledi Chamber are still uncertain. During the 2017���2018 field seasons, we expanded explorations of the passages surrounding the Dinaledi Chamber. These explorations improved our understanding of the cave���s spatial complexity, necessitating a revision of the way the spaces are named and described. The work supported the hypothesis that there is no alternate entrance into the system other than the Chute. The work also identified new fossil deposits in several remote passages, three of which contain material attributable to H. naledi. Here, we clarify the definition of the Dinaledi Subsystem and provide terminology for new fossil localities found in this portion of the Rising Star cave system. These results emphasize the complex depositional environment of the Dinaledi Subsystem and raise new questions about the process and timing of the fossil accumulations., PaleoAnthropology, 2021: PaleoAnthropology

In 1996, Grün and coworkers provided an ESR age determination for a hominin molar from Florisbad, South Africa, at 259 ± 35 ka. The most anatomically informative hominin specimen from Florisbad is a fragmentary craniofacial specimen, attributed by many to early Homo sapiens, which has been assumed to derive from the same individual as this tooth. Since 1996, evidence about the evolutionary context for the later Middle Pleistocene and its associated hominins in Africa had markedly changed. If the Florisbad date is accurate and if the molar is associated with the craniofacial specimen, this evidence may suggest that Homo naledi coexisted in time and geography with H. sapiens in southern Africa. Thus, the accuracy for all dates needs critical investigation. This study examines the published record of excavation and subsequent analyses for the Florisbad material. We find that the contemporary records raise doubt about the contemporaneity of the tooth and calvaria. The site’s complex stratigraphy and the details about the tooth’s discovery also pose challenges for the previous ESR age estimate. Because the fragmentary cranial specimen has value for morphological comparisons, developing additional means of understanding its geological age is necessary. The current data do not demonstrate the presence of H. sapiens in southern Africa at ~260 ka.

International audience; The upper limb of Homo naledi has previously been described from fragmentary material discovered in the Dinaledi Chamber in the Rising Star cave system, Cradle of Humankind, South Africa. Recent work at Rising Star has led to the recovery of additional fossil material attributed to H. naledi from a new fossil site within the system called the Lesedi Chamber. The new fossil material preserves the upper limb elements from a partial skeleton of a single individual (LES 1). Crucially, the upper limb material from Lesedi preserves functionally significant aspects of morphology missing from the Dinaledi assemblage, including a well-preserved proximal humerus, a complete clavicle, and proximal ulna. The primitive humeral morphology of the Dinaledi material is replicated within the Lesedi material. Curvature analysis of the Lesedi clavicle revealed that the claviculae of H. naledi are similarly primitive, supporting previous interpretations of the H. naledi shoulder as being more superiorly positioned than modern humans, and closer to the hypothesized Australopith condition. Multivariate analysis of the LES 1 proximal ulna demonstrate the overall similarity of the LES 1 ulna to the KNM-BK 66 ulna from Baringo (provisionally attributed to H. erectus). While KNM-BK 66 fell closer than LES 1 to the australopith centroid along major components of variation, both ulnae clustered more with australopiths and Neandertals than with modern humans. These new findings support the presence of Homo naledi in multiple depositional contexts within the Rising Star System and provide a clearer picture of the upper limb morphology of this species.