Early hominin speciation at the Plio/Pleistocene transition

Over the last half-decade or so, there has been an explosion in the recognition of hominin genera and species. We now have the late Miocene genera Orrorin and Sahelanthropus, the mid Pliocene genus Kenyanthropus, three new Pliocene species of Australopithecus (A. anamensis, A. garhi and A. bahrelghazali) and a sub species of Ardipithecus (Ar. r. kadabba) to contend with. Excepting also the more traditional species allocated to Paranthropus, Australopithecus and early Homo we are approaching around 15 species over 5 million years (excluding hominin evolution over the last one million years). Can such a large number of hominin species be justified? An examination of extant hominid (Gorilla gorilla, Pan troglodytes, and Pan paniscus) anatomical variability indicates that the range of fossil hominin variability supports the recognition of this large number of fossil species. It is also shown that not all hominins are directly related to the emergence of early Homo and as such have become extinct. Indeed the traditional australopithecine species 'A'. anamensis, 'A'. afarensis and 'A'. garhi are considered here to belong to a distinct genus Praeanthropus. They are also argued not be hominins, but rather an as yet undefined hominid group from which the more derived hominins evolved. The first hominin is represented by A. africanus or a hominin very much like it. The Paranthropus clade is defined by a derived heterochronic condition of peramorphosis, associated with sequential progenesis (contraction of successive growth stages) in brain and dental development, but a mixture of peramorphic and paedomorphic features in its craniofacial anatomy. Conversely, Kenyanthropus and Homo both share a pattern of peramorphosis, associated with sequential hypermorphosis (prolongation of successive growth stages) in brain development, and paedomorphosis processes in cranial, facial and dental development. This suggests, that these two clades share an important synapomorphy not recognised in the parsimony analyses, suggesting that they may form a sister group relationship to the exclusion of Paranthropus. This highlights the need to re-interpret phylogenetic results in terms of function and development. The rapid speciation and extinction as argued here is in keeping with other fossil groups in Africa at the Plio/Pleistocene transition. This emphasises that we must approach the pre-australopithecines and hominins as part of the endemic African fauna, and not in isolation to the evolutionary and climatic processes that were operating all around them.     

Human mandibular incisors from the late Middle Pleistocene locality of Hoedjiespunt 1, South Africa.

The Hoedjiespunt 1 locality is an archaeological and palaeontological site located on the Hoedjiespunt Peninsula at Saldanha Bay, South Africa. In 1996 two human teeth, a left central mandibular incisor and a left lateral mandibular incisor, were discovered during excavations in the late Middle Pleistocene palaeontological layers. These teeth are described and are found to belong to a single subadult individual. Despite their developmental stage, these incisors already display early signs of wear. Their crown diameters are larger than modern and archaeological African comparative material and are most closely comparable with crown diameters of an early Middle Pleistocene and late Middle Pleistocene dental sample from Africa, Europe and Asia. In the light of this metrical evidence, data on two previously excavated maxillary molars, most probably belonging to the same individual, were re-examined. It was found that the Hoedjiespunt 1 hominid possessed dental metrical features (large anterior teeth and small molars) comparable with other African and European hominids referred to the Middle Pleistocene.     

The Casal de' Pazzi archaic parietal: comparative analysis of new fossil evidence from the late Middle Pleistocene of Rome

A fossilized fragment of human parietal bone has been recently recovered from the lowest layer of the Casal de' Pazzi fluvial deposit (stratigraphically dated at about 200–250 ky BP). The fossil presents characters-i.e., thickness, degree and development of curvature, type of endocranial vascularization-which distinguish it from the corresponding cranial regions of both Homo erectus and anatomically modern Homo sapiens. While a morphological orientation towards Neanderthal characters can be considered, the affinities of the Casal de' Pazzi parietal are primarily with other late Middle Pleistocene specimens. The authors conclude that the Casal de' Pazzi human find can be assigned to the “archaic Homo sapiens” group falling within the European pre-Neanderthal range. Its particular morphology constitutes new evidence of human evolution from the geographical area of Rome.     

Nacholapithecus skeleton from the Middle Miocene of Kenya

An almost entire skeleton of a male individual of Nacholapithecus kerioi (KNM-BG 35250) was discovered from Middle Miocene (approximately 15 Ma) sediments at Nachola, northern Kenya. N. kerioi exhibits a shared derived subnasal morphology with living apes. In many postcranial features, such as articular shape, as well as the number of the lumbar vertebrae, N. kerioi resembles Proconsul heseloni and/or P. nyanzae, and lacks suspensory specializations characteristic of living apes. Similarly, N. kerioi shares some postcranial characters with Kenyapithecus spp. However, despite the resemblance, N. kerioi and Proconsul spp. are quite different in their body proportions and some joint morphologies. N. kerioi has proportionally large forelimb bones and long pedal digits compared to its hindlimb bones and lumbar vertebrae. Its distinctive body proportions suggest that N. kerioi was more derived for forelimb dominated arboreal activities than P. nyanzae and P. heseloni. On the other hand, it exhibits a mixture of derived and primitive cranio-dental and postcranial features relative to the contemporaneous Kenyapithecus and Early MioceneMorotopithecus. While the phylogenetic position of N. kerioi is unsettled, it seems necessary to posit parallel evolution of cranio-dental and/or postcranial features in fossil and living apes.     

Nuclear DNA sequences from late Pleistocene megafauna

We report the retrieval and characterization of multi- and single-copynuclear DNA sequences from Alaskan and Siberian mammoths (Mammuthusprimigenius). In addition, a nuclear copy of a mitochondrial gene wasrecovered. Furthermore, a 13,000-year-old ground sloth and a 33,000-year-old cave bear yielded multicopy nuclear DNA sequences. Thus, multicopyand single-copy genes can be analyzed from Pleistocene faunal remains. Theresults also show that under some circumstances, nucleotide sequencedifferences between alleles found within one individual can bedistinguished from DNA sequence variation caused by postmortem DNA damage.The nuclear sequences retrieved from the mammoths suggest that mammothswere more similar to Asian elephants than to African elephants.     

Two hominin incisor teeth from the middle Pleistocene site of Boxgrove, Sussex, England

In 1995-1996 two isolated hominin lower incisors were found at the middle Pleistocene site of Boxgrove in England, with Lower Palaeolithic archaeology. Boxgrove 2 is a permanent lower right central incisor and Boxgrove 3 a permanent lower left lateral incisor. They were found separately, but close to one another and appear to belong to the same individual. The Boxgrove 1 tibia discovered in 1993 came from a different stratigraphic context and is thus believed to represent a different individual. This paper describes the morphology of the incisors, which is similar to other middle Pleistocene hominin specimens and, as with the tibia, suggests that they could be assigned to Homo heidelbergensis (recognising that the taxonomic status of this species is still a matter of debate). The incisors show substantial attrition associated with secondary dentine deposition in the pulp chamber and clearly represent an adult. They also show extensive patterns of non-masticatory scratches on the labial surfaces of both crown and root, including some marks which may have been made postmortem. The roots were exposed in life on their labial sides by a large dehiscence, extending almost to the root apex. This is demonstrated by deposits of calculus, polishing, and scratching on the exposed surfaces. The dehiscence may have been caused by repeated trauma to the gingivae or remodelling of the tooth-supporting tissues in response to large forces applied to the front of the dentition.     

Middle and late Pleistocene faunas of Pinnacle Point and their paleoecological implications

The Western Cape region of South Africa is home to a unique type of mediterranean vegetation called fynbos, as well as some of the earliest sites of modern human occupation in southern Africa. Reconstructing the paleohabitats during occupations of these early anatomically modern Homo sapiens is important for understanding the availability of resources to the humans during the development of behaviors that are often considered advanced. These reconstructions are critical to understanding the nature of the changes in the environment and resources over time. Here we analyze the craniodental fossils of the larger mammals recovered from two Pleistocene assemblages in the Pinnacle Point complex, Mossel Bay, Western Cape Region, South Africa. We reconstruct the paleohabitats as revealed by multivariate analyses of the mammalian community structures. Pinnacle Point 30 is a carnivore assemblage and Pinnacle Point 13B includes early evidence of a suite of modern human behavior; together they present an opportunity to identify environmental change over time at a localized geographic scale. Further, this is the first such study to include dated Western Cape localities from Marine Isotope Stage 6, a time of environmental pressure that may have marginalized human populations. Results indicate that environmental change in the Western Cape was more complex than generalized C(4) grassland expansions replacing fynbos habitats during glacial lowered sea levels, and thus, resources available to early modern humans in the region may not have been entirely predictable.     

Middle Pleistocene human remains from the Bau de l'Aubesier

Excavations in later Middle Pleistocene levels at the Bau de l'Aubesier, Vaucluse, France yielded a maxillary molar (M(1) or M(2); Aubesier 10) and a partial mandible from the left C(1) alveolus to the right condylar base lacking the coronoid process (Aubesier 11). Dentally they are similar to other later Middle Pleistocene Europeans in dental dimensions and variable taurodontism (Aubesier 10 but not Aubesier 11). The small Aubesier 11 mandible exhibits a retreating symphyseal profile with a minimal tuber symphyseos, an anterior marginal tubercle at P(4)/M(1), the mental foramen at P(4)/M(1)-M(1), a modest retromolar space, no lingular bridging of the mandibular foramen, an enlarged superior medial pterygoid tubercle, a modest lateral condylar tubercle, and a mandibular notch crest that intersects the middle third of the condylar margin. All of these features fall within the ranges of variation of later Middle Pleistocene Neandertal lineage humans, and some are characteristic of Middle Pleistocene human mandibles in general. In addition, Aubesier 11 exhibits pervasive ante mortem alveolar resorption with apical abscesses, alveolar bone destruction, universal labial/buccal bone loss, ante mortem tooth loss (for > or =81.8% of preserved alveoli), a lingual alveolar fenestration, and two broken root apices with masticatory attrition. These lesions indicate significantly impaired masticatory function, the oldest specimen currently known with such a reduced degree of dental function but one of several Middle Pleistocene human remains with indications of serious abnormalities.     

A comparative study of frontal bone morphology among Pleistocene hominin fossil groups

Features of the frontal bone that are conventionally used to distinguish among fossil hominin groups were quantitatively examined. Fifty-five fossil crania dating from the early to the late Pleistocene were analyzed. Using a modified pantograph, outlines of the frontal bone were collected along the midsagittal and two parasagittal planes. The profile from nasion to bregma, as well as two profiles above the medial and lateral sections of the orbit, respectively, extending from the orbital margin to the coronal suture were traced. The outlines were measured using Elliptical Fourier Function Analysis (EFFA), which enabled a quantification of aspects of the frontal bone that have historically been described primarily in nonmetric or linear terms. Four measurements were obtained: 1) overall morphology as expressed in the Fourier harmonic amplitudes; 2) maximum projection of the supraorbital torus at three points along the browridge (glabella and the medial and lateral aspects of the torus above the orbit); 3) maximum distance of the frontal squama from the frontal chord, capturing forehead curvature; and 4) nasion-bregma chord length. The results indicate that the midsagittal profile is significantly different among all Pleistocene groups in analyses that include both size and shape, as well as size-adjusted data. Homo erectus is significantly different from the late Pleistocene groups (Neandertals and early modern H. sapiens) in glabellar projection. Anatomically modern humans are significantly different from all other groups in both raw and size-standardized analyses of all three outlines that captured overall morphology, as well as forehead curvature and lateral supraorbital torus prominence, and middle Pleistocene Homo are significantly different in both medial and lateral overall parasagittal form. However, for the majority of analyses there were no significant differences among the Pleistocene archaic groups in supraorbital torus projection, frontal squama curvature, nasion-bregma chord length, or overall frontal bone morphology.     

Middle Pleistocene hominids from Olduvai Gorge, northern Tanzania

Cranial, dental, and mandibular remains of eight Olduvai hominids are described in detail. Four individuals were recovered in situ in Beds II to IV, while three more are most probably derived from Bed IV, the Masek Beds and the Lower Ndutu Beds. One specimen is of uncertain provenance. Deposits from which the fossils were collected range from late Lower Pleistocene to Middle Pleistocene in age. Of particular interest are three fragmentary lower jaws, which can be compared to mandibles of Homo erectus known from localities in Northwest Africa and China. Olduvai hominid 22, a nearly complete half mandible with crowns of P3-M2 in place, shares many anatomical features with fossils from Ternifine and Choukoutien. This individual is also similar to a jaw from the Kapthurin Formation west of Lake Baringo, Kenya. How best to interpret these comparisons is not clear, but in view of marked similarities between specimens representing geographically diverse populations from different time periods, it may be unwise to rely on mandibular evidence alone to document the presence of regional lineages. Gradual change and continuity within a sequence of Northwest African Homo fossils has been endorsed by many workers, but such hypotheses cannot be tested adequately with the fragmentary jaws available.     

Lethal Interpersonal Violence in the Middle Pleistocene

Evidence of interpersonal violence has been documented previously in Pleistocene members of the genus Homo, but only very rarely has this been posited as the possible manner of death. Here we report the earliest evidence of lethal interpersonal violence in the hominin fossil record. Cranium 17 recovered from the Sima de los Huesos Middle Pleistocene site shows two clear perimortem depression fractures on the frontal bone, interpreted as being produced by two episodes of localized blunt force trauma. The type of injuries, their location, the strong similarity of the fractures in shape and size, and the different orientations and implied trajectories of the two fractures suggest they were produced with the same object in face-to-face interpersonal conflict. Given that either of the two traumatic events was likely lethal, the presence of multiple blows implies an intention to kill. This finding shows that the lethal interpersonal violence is an ancient human behavior and has important implications for the accumulation of bodies at the site, supporting an anthropic origin.     

Middle and late Pleistocene Middle Stone Age lithic technology from Pinnacle Point 13B (Mossel Bay, Western Cape Province, South Africa)

Excavations at a complex of caves and open air sites at Pinnacle Point, Mossel Bay, Southern Africa have uncovered rich stratified assemblages of Middle Stone Age materials, including those from Pinnacle Point Cave 13B (PP13B) that comprises the first modernly excavated assemblage in southern Africa to be securely dated to the Middle Pleistocene. We report here on the complete excavated lithic artifact assemblage from PP13B. Both technological and typological analyses of the complete assemblage were performed. The assemblage-scale analysis allows for intrasite comparison as well as comparison of the PP13B assemblage with other sites from the region. No size-related pattern of change over time was observed within the PP13B assemblage, although there is significant evidence for varying strategies of lithic reduction between excavation areas within the cave. Comparison with other material from the Southern African MSA suggests that there is significant inter- and intra-site variability in the Southern African Middle Stone Age, even between portions of assemblages that are roughly contemporaneous.     

Krapina 1: a juvenile Neandertal from the early late Pleistocene of Croatia

The juvenile A Skull from Krapina, Croatia (Krapina 1) has been the subject of considerable debate since B. Skerlj first suggested that it might not be a Neandertal. Although widely known by its original designation, the Krapina A Skull was recatalogued, along with all of the Krapina hominids, in the 1980's (Radovcic, et al., [1988]. The Krapina Hominids: An Illustrated Catalog of Skeletal Collection. Zagreb; Mladost). It is now catalogued as Krapina 1 in the archives of the Hrvatski Prirodoslovni Muzej, Zagreb, Croatia. We present a detailed, morphometric analysis of this specimen, comparing it to other Krapina specimens, juvenile late Pleistocene hominids (including Neandertals), and subadult recent humans. This analysis demonstrates that Krapina 1 possesses morphological features that are primitive retentions; others that represent derived Neandertal specializations; and still others that are typical for all European late Pleistocene humans. Morphological features associated with the browridges are intermediate between Neandertal and early modern European form. Nevertheless, a thorough analysis of the morphology of this specimen, in ontogenetic and regional contexts, leads to the conclusion that it cannot be excluded from the Neandertal range of variation. We conclude that the most parsimonious explanation for this 130 ka specimen is that it should be regarded as a Neandertal.     

An Early Pleistocene human pedal phalanx from Swartkrans,SKX 16699, and the antiquity of the human lateral forefoot

In order to assess the antiquity of derived human lateral (lesser) toe morphology, the SKX 16699 Early Pleistocene pedal proximal phalanx from Swartkrans (South Africa) was compared to samples of pedal phalanges attributed to Pliocene/Pleistocene australopithecines, Homo naledi and Late Pleistocene Homo. In contrast to australopith lateral phalanges, the SKX 16699 phalanx exhibits an absolutely (and probably relatively) short length, limited plantar diaphyseal curvature, proximal-to-midshaft and mid-dorsoplantar flexor sheath insertions, and a marked proximodorsal orientation of the metatarsal facet. SKX 16699 is intermediate between the australopith phalanges and later Homo ones in its modest dorsal diaphyseal curvature and mid-dorsoplantar metatarsophalangeal collateral ligament insertion areas. Its diaphyseal robustness is similar to that of Homo phalanges, but overlaps the range of later australopith ones. This combination of features and the close morphological affinities of SKX 16699 to later Homo proximal pedal phalanges suggest the emergence of a distinctly human lateral forefoot by the initial Early Pleistocene.