Journal of Human Evolution最新文献

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.

As a potential corridor connecting Southwest Asia with western and northern Europe, the Armenian Highlands and southern Caucasus hold great potential for increasing our understanding of Upper Paleolithic behavioral and cultural variability. However, given the dearth of Upper Paleolithic sites, we lack the data necessary to answer basic questions regarding the timing and nature of the Upper Paleolithic in this region. Solak-1 is an open-air site located along the upper Hrazdan Valley (1635 m above sea level) in central Armenia. The site preserves a rich Upper Paleolithic lithic assemblage produced almost exclusively on obsidian and is just the fourth Upper Paleolithic sequence in Armenia. The goal of this study is to present geoarchaeological, chronometric, and technological analyses of the Solak-1 site to integrate the site into the regional Upper Paleolithic sequence. Solak-1 is composed of six lithostratigraphic units (LUs 1-6) comprising recently reworked (LUs 1-2), pedogenically modified (LUs 3-5), and primary (LU 6) loess. A single-grain postinfrared infrared stimulated luminescence date of 27.73 ± 3.63 ka was obtained from LU 4. This age is comparable to regional Middle Upper Paleolithic sites in Armenia and Georgia. Technotypological analyses indicate a lithic assemblage dominated by the production of bladelets and bladelet tools from formal and informal cores. Geochemical sourcing of the obsidian highlights a predominance of local raw material use, with rare transport of artifacts over 185 linear km. These results add an important new datapoint to the Upper Paleolithic record of the Armenian Highlands, offering additional insights into technotypological patterning within this period.

Samburupithecus kiptalami is an ape found in Late Miocene deposits (ca. 9.5 Ma) of northern Kenya. Initial assessments of the holotype specimen (KNM-SH 8531), a female-gorilla-sized maxillary fragment preserving the postcanine tooth row, noted similarities to gorillas or to African apes more broadly. More recently, primitive features of the maxilla and dentition have been used to propose a stem hominoid position for Samburupithecus. In particular, Samburupithecus shares some dental features with orepithecids (nyanzapithecines and Oreopithecus). To evaluate these competing hypotheses, and investigate possible affinities to oreopithecids, we reanalyzed the dentition of Samburupithecus quantitatively and assessed qualitative dental and maxillary features shared by oreopithecids and Samburupithecus. Based on the results of our analyses, we suggest that Samburupithecus is a late-occurring African oreopithecid, which we regard as a long-lived family of stem hominoids. The inclusion of Samburupithecus within Oreopithecidae highlights that stem hominoids and oreopithecids, in particular, spanned a large range of body sizes, similar to the range of size variation seen among all extant apes. Finally, the presence of oreopithecids in Africa on either side of a notable gap in the Late Miocene African fossil record of apes (from ∼13 to 10 Ma) demonstrates that the rarity of fossil African apes (i.e., nonhominin hominines) during this period is likely due to sampling biases rather than a recent immigration back into Africa from Eurasia.

The hominin mandible SK 15 was discovered in April 1949 in Swartkrans Member 2, dated to ∼1.4 Ma. Albeit distorted on the right side, the left and right corpus of SK 15 are relatively low and thick, even compared to most Early to Middle Pleistocene Homo specimens. It preserves the left molar row and the right M₂ and M₃ that show a distalward increase in mesiodistal diameter. SK 15 was originally attributed to Telanthropus capensis but is now generally attributed to Homo erectus/Homo ergaster, even if it was previously suggested to possibly belong to Australopithecus. Similarities between SK 15 and Homo naledi mandible and tooth morphology were also claimed. To clarify the taxonomy of SK 15, we used X-ray microtomography to investigate aspects of bone and tooth structural organization. Geometric morphometric analyses of the dental arcade shape, mandible symphysis outline, and the M₂ and M₃ enamel-dentine junction shape were conducted. For mandibular symphysis shape, SK 15 exhibits an australopith signal, whereas for both the dental arcade and enamel-dentine junction analyses, the specimen is statistically classified as Paranthropus. Altogether, the results show that SK 15 unambiguously falls outside the variation of H. erectus/H. ergaster and that it is most compatible with the morphology of Paranthropus, albeit showing smaller dimensions and an absence of some dental morphological features (e.g., developed protostylid, distally tapering M₃, short molar roots) typically found in specimens of Paranthropus aethiopicus, Paranthropus boisei, and Paranthropus robustus. In particular, SK 15 differs markedly in size and morphology from mandibular remains of P. robustus from Swartkrans Member 2. We thus tentatively attribute SK 15 to Paranthropus capensis, a more gracile species of Paranthropus than the other three currently recognized species of this genus and discuss the implications for the existence of another species of Paranthropus in southern Africa during the Early Pleistocene.

Childhood and adolescence are two life-history stages that are either unique to humans, or significantly expanded in the human life course relative to other primates. While recent studies have deepened our knowledge of childhood in the Upper Paleolithic, adolescence in this period remains understudied. Here, we use bioarchaeological maturational markers to estimate puberty status of 13 Upper Paleolithic adolescents from sites in Russia, Czechia, and Italy to 1) evaluate the feasibility of the application of bioarchaeological puberty assessment methods to Upper Paleolithic (Homo sapiens) skeletal individuals, 2) estimate the timing and tempo of puberty in Upper Paleolithic adolescents compared to other archaeological populations analyzed using the same method, and 3) characterize adolescence in the Upper Paleolithic by contextualizing the results of this puberty assessment with data on individual and population-level health, morbidity and burial practices. Our results revealed that while puberty had begun by 13.5 years of age for the majority of individuals, there was a lot of variability, with the adolescents from Arene Candide (AC1 and AC16), both aged around 16 years when they died, taking several years longer to progress through puberty than their peers. Assessing the age of menarche was challenging due to the paucity of female adolescents, but based on the available evidence, it appears to have occurred between 16 and 17 years of age. For some, full adulthood had been achieved by 17-22 years, similar to the patterns seen in modern wealthy countries and in advance of historic populations living in urbanized environments. The bioarchaeological analysis of puberty among Upper Paleolithic adolescents has important implications for the study of the emergence of adolescence within human-life histories, as well as for understanding the developmental plasticity of sexual maturation across past and present human populations.

The degree of sexual size dimorphism in fossil hominins is important evidence for the evaluation of evolutionary hypotheses, but it is also difficult/impossible to measure directly. Multiple methods have been developed to estimate dimorphism in univariate and multivariate datasets, including when data are missing. This paper introduces 'dimorph', an R package that implements many of these methods and associated resampling-based significance tests and evaluates their performance in terms of Type I error rates and power. Tests evaluated here are those that appear most commonly in the hominin literature: testing whether a fossil sample is significantly more dimorphic than a comparative sample of known dimorphism. Univariate and multivariate methods are applied to metric data from four extant hominoid species: Gorilla gorilla, Homo sapiens, Pan troglodytes, and Hylobates lar. Each species is represented by 47 female and 47 male adult individuals, from which 10 linear postcranial measurements are collected. Data are resampled at a broad range of sample sizes (n = 4 to n = 82), sex ratios (proportion of females range from 0 to 1), and in the case of missing-data methods, proportions of missing data (0-0.9). Type I error rates and power are evaluated by the proportion of tests correctly or incorrectly rejecting null hypotheses regarding dimorphism difference within pairs of samples drawn from these four species, in which one sample stands in for a fossil sample. Results indicate low Type I error rates for all methods, whereas power is variable across methods but often low at sample sizes common to fossil analyses. Recommendations are made for the best significance tests. Additionally, previous work using lack of significant difference as evidence for similarity in dimorphism between fossils and extant species should be re-examined to determine whether those studies have enough power to detect known differences among extant taxa.

The Grotte du Bison, in Arcy-sur-Cure (Yonne, France), yielded a large assemblage of 49 Neandertal remains from late Mousterian layers, offering critical insights for the study of Middle to Upper Paleolithic populations of Western Europe. Previous studies described the external morphology of 13 isolated teeth and a partial maxilla. Building on this previous work, the current study provides further descriptions and analyses of the remains, including one postcranial fragment, six cranial fragments, two maxillary fragments, and 40 isolated teeth. The dental remains are examined for a more detailed assessment of the metric and nonmetric variability of their external and internal morphologies. We focus our description on preservation, health status, and age at death, and we assess the minimum number of individuals. The dental variability is also compared to that of Middle and Upper Pleistocene hominins. Our results indicate that the collection represents at least nine to 17 individuals, comprising mostly children and adolescents. Five to seven pairings are identified based on shared dental traits, developmental criteria, such as perikymata and pitted hypoplasia, wear patterns, and taphonomic alterations. This collection exhibits characteristic Neandertal features, including occasionally markedly expressed traits (e.g., I¹ and P³ ridging and tubercular expressions), as well as a homogenous expression of accessory structures (particularly for the molars). The highest morphological variability is observed on maxillary premolar roots, which display different stages of root fusion, mesially placed hypercementosis, and pulp cavity extension. This collection also reflects the morphological and behavioral diversity observed in the other Arcy-sur-Cure caves.

The use of broad tool repertoires to increase dietary flexibility through extractive foraging behaviors is shared by humans and their closest living relatives (chimpanzees, Pan troglodytes). However, comparisons between tool use in ancient human ancestors (hominins) and chimpanzees are limited by differences in their toolkits. One feature shared by primate and hominin toolkits is rock selection based on physical properties of the stones and the targets of foraging behaviors. Here, we document the selectivity patterns of stone tools used by wild chimpanzees to crack nuts at Bossou, Guinea, through controlled experiments that introduce rocks unknown to this population. Experiments incorporate specific rock types because previous studies document hominin selection of these lithologies at Kanjera South 2 Ma. We investigate decisions made by chimpanzees when selecting stones that vary in their mechanical properties-features not directly visible to the individual. Results indicate that the selection of anvils and hammers is linked to task-specific mechanical properties. Chimpanzees select harder stones for hammers and softer stones for anvils, indicating an understanding of specific properties for distinct functions. Selectivity of rock types suggests that chimpanzees assess the appropriate materials for functions by discriminating these 'invisible' properties. Adults identify mechanical properties through individual learning, and juveniles often reused the tools selected by adults. Selection of specific rock types may be transmitted through the reuse of combinations of rocks. These patterns of stone selection parallel what is documented for Oldowan hominins. The processes identified in this experiment provide insights into the discrete nature of hominin rock selection patterns in Plio-Pleistocene stone artifact production.