In primates and other mammals, the capacity to generate a wide maximum jaw gape is an important performance variable related to both feeding and nonfeeding oral behaviors, such as canine gape display and clearing the canines for use as weapons during aggressive encounters. Across sexually dimorphic catarrhine primates, gape is significantly correlated with canine height and with musculoskeletal features that facilitate wide gapes. Given the importance of canine gape behaviors in males as part of intrasexual competition for females, functional relationships between gape, canine height, and musculoskeletal morphology can be predicted to differ between the sexes. We test this hypothesis by investigating sex-specific relationships among these variables in a maximum sample of 32 cercopithecoid species. Using phylogenetic least squares regression, we found that of 18 predicted relationships, 16 of the 18 (89%) were significant in males, whereas only six (33%) were significant in females. Moreover, 15 of the 18 correlations were higher-10 of the 18 significantly higher-in males than in females. Males, but not females, showed strong and significant positive allometry of fiber lengths, indicating that increase in male jaw length is accompanied by allometric increases in the capacity for muscle stretch. While males and females showed significant negative allometry for muscle leverage, only males showed significant negative allometry of muscle leverage relative to jaw gape and canine height. Collectively, these results provide support for the hypothesis that as selection acted to increase relative canine height in male cercopithecoids, one change was an allometric increase in relative maximum jaw gape, along with allometric increases in musculoskeletal morphologies that facilitate gape. Lastly, if gape and canine display/clearance are key targets of selection on masticatory morphology in male cercopithecoids, then cercopithecoid monkeys such as macaques, baboons, and sooty mangabeys may have diminished utility as models for drawing paleobiological inferences from musculoskeletal morphology about feeding behavior and diet in fossil hominins.

Reconstructing habitat types available to hominins and inferring how the paleo-landscape changed through time are critical steps in testing hypotheses about the selective pressures that drove the emergence of bipedalism, tool use, a change in diet, and progressive encephalization. Change in the amount and distribution of woody vegetation has been suggested as one of the important factors that shaped early hominin evolution. Previous models for reconstructing woody cover at eastern African hominin fossil sites used global-scale modern soil comparative datasets. Our higher-spatial-resolution study of carbon isotopes in soil organic matter is based on 26 modern African locations, ranging from tropical grass-dominated savannas to forests. We used this dataset to generate a new Eastern Africa-specific Woody Cover Model (EAWCM), which indicates that eastern African hominin sites were up to 13% more wooded than reconstructions based on previous models. Reconstructions using the EAWCM indicate widespread woodlands/bushlands and wooded grasslands and a shift toward C-dominated landscapes in eastern Africa over the last 6 million years. Our results indicate that mixed tree-C grass savannas with 10-80% tree cover (but not pure grasslands with <10 % tree cover) dominated early hominin paleoenvironments. Landscapes with these biomes are marked by exceptional heterogeneity, which posed challenges and offered opportunities to early hominins that likely contributed to major behavioral and morphological shifts in the hominin clade.

The transition between the Bridgerian and Uintan North American Land Mammal Ages of the middle Eocene is a pivotal time in the evolution of modern mammal ecosystems in North America, marking the beginning of a global cooling trend that led to the recession of tropical forests and gradual faunal turnover on the continent. However, few mammalian faunas are known from this time period, leading to difficulty characterizing and recognizing early Uintan faunal assemblages. The Sand Wash Basin in northwestern Colorado has been suggested to yield fossil faunas of early Uintan age, but fossils from the Sand Wash Basin have not been formally described since the 1970s despite active field work in the region. Here, I describe plesiadapiform and euprimate fossils from the Sand Wash Basin and compare them to other late Bridgerian and early Uintan North American primate assemblages. The Sand Wash Basin primate fauna comprises five species, all of which are known from the Washakie Basin in Wyoming. The presence of Ourayia uintensis suggests that at least some fossil localities within the Sand Wash Basin yield fossils that are Uintan in age; however, the rarity of primates and lack of a stratigraphic context in which to interpret localities make it difficult to determine whether some may be older.

Here we describe new fossil material of Antillothrix bernensis, a Pleistocene-Holocene primate taxon from Hispaniola. It is now represented by seven crania, five mandibles, and dozens of postcranial elements from several paleontologically rich cave systems. The five adult crania included here share a similar overall profile as well as specific features such as a deep depression at the glabella. The complete anterior dentition of Antillothrix can now be described for the first time; short canine crowns, in the apicobasal dimension, compare well with titi monkeys, but the new crania and mandibles lack the specialized tall-crowned incisors of the extant pitheciids. They do, however, have a diastema between the lateral maxillary incisors and canines, a feature not present in the previously known crania. The new mandibles deepen posteriorly and have a medial inflection of the mandibular ramus, as in some pitheciids, but also share with Xenothrix a significant vertical narrowing of the corpus under P/M not observed among extant taxa. Two of the specimens, a cranium and a mandible that do not fit together, exhibit congenitally absent third molars-a rarity among extant, noncallitrichine taxa. There is an approximately 1-kg range in the estimated body mass among the full Antillothrix sample (from 2.4 to 3.4 kg), as well as a range of approximately 5 cm of endocranial volume (from 40 to 45 cm). With these extended ranges from the new specimens, Antillothrix can no longer be described as a taxon with a brain size smaller than that expected for its body size. Neither of these ranges in the brain size or body size is large enough to indicate a substantial level of sexual dimorphism or to necessitate separating the sample into male and female individuals. Given this, and the similar canine sizes for all specimens where they are present, the sample is consistent with a morphologically variable but monomorphic species.

The Schöningen 13II-4 site is a marvel of Paleolithic archaeology. With the extraordinary preservation of complete wooden spears and butchered large mammal bones dating from the Middle Pleistocene, Schöningen maintains a prominent position in the halls of human origins worldwide. Here, we present the first analysis of the complete large mammal faunal assemblage from Schöningen 13II-4, drawing on multiple lines of zooarchaeological and taphonomic evidence to expose the full spectrum of hominin activities at the site-before, during, and after the hunt. Horse (Equus mosbachensis) remains dominate the assemblage and suggest a recurrent ambush hunting strategy along the margins of the Schöningen paleo-lake. In this regard, Schöningen 13II-4 provides the first undisputed evidence for hunting of a single prey species that can be studied from an in situ, open-air context. The Schöningen hominins likely relied on cooperative hunting strategy to target horse family groups, to the near exclusion of bachelor herds. Horse kills occurred during all seasons, implying a year-round presence of hominins on the Schöningen landscape. All portions of prey skeletons are represented in the assemblage, many complete and in semiarticulation, with little transport of skeletal parts away from the site. Butchery marks are abundant, and adult carcasses were processed more thoroughly than were juveniles. Numerous complete, unmodified bones indicated that lean meat and marrow were not always so highly prized, especially in events involving multiple kills when fat and animal hides may have received greater attention. The behaviors displayed at Schöningen continue to challenge our perceptions and models of past hominin lifeways, further cementing Schöningen's standing as the archetype for understanding hunting adaptations during the European Middle Pleistocene.

Grotte Mandrin is located in the middle Rhône River Valley, in Mediterranean France, and has yielded 11 Pleistocene archeological and paleoanthropological layers (ranging from the oldest layer J to the youngest layer B) dating from Marine Isotope Stage (MIS) 5 to MIS 3. We report here the nearly complete dentition of an adult Neanderthal individual, nicknamed 'Thorin,' associated to the last phase of the Post-Neronian II, in layer B2 (∼44.50-42.25 ka). A previous paleogenetic analysis revealed that Thorin is a male individual and that he shows a deep genetic divergence with other penecontemporaneous Neanderthals from western Europe that possibly occurred ∼105 ka. The 31 teeth of Thorin (including two distomolars) are described and analyzed using microcomputed tomography imaging and are compared with other Neanderthals and modern humans. Based on direct observation and measurements on the fossil remains, and using microtomographic imaging, tooth wear, nonmetric characters, crown dimensions, and dental tissue proportions were investigated, and the shape of the enamel-dentine junction of the M, M, and M was analyzed by geometric morphometrics. Our results indicate that Thorin's teeth show dental characteristics typical of MIS 5-3 Neanderthals. It is also the first time that the presence of two distomolars is reported in a Neanderthal individual, a trait that is rare among modern human populations. Combined with the genetic peculiarities of this individual, the results of the present study imply either a process of morphological convergence among the latest Neanderthal groups or an underestimation of the genetic variability of recent Neanderthal groups.

The evolution of the human hand is a topic of great interest in paleoanthropology. As the hand can be involved in a vast array of activities, knowledge regarding how it was used by early hominins can yield crucial information on the factors driving biocultural evolution. Previous research on early hominin hands focused on the overall bone shape. However, while such approaches can inform on mechanical abilities and the evolved efficiency of manipulation, they cannot be used as a definite proxy for individual habitual activity. Accordingly, it is crucial to examine bone structures more responsive to lifetime biomechanical loading, such as muscle attachment sites or internal bone architecture. In this study, we investigate the manual entheseal patterns of Australopithecus afarensis, Australopithecus africanus, and Australopithecus sediba through the application of the validated entheses-based reconstruction of activity method. Using a comparative sample of later Homo and three great ape genera, we analyze the muscle attachment site proportions on the thumb, fifth ray, and third intermediate phalanx to gain insight into the habitual hand use of Australopithecus. We use a novel statistical procedure to account for the effects of interspecies variation in overall size and ray proportions. Our results highlight the importance of certain muscles of the first and fifth digits for humanlike hand use. In humans, these muscles are required for variable in-hand manipulation and are activated during stone-tool production. The entheses of A. sediba suggest muscle activation patterns consistent with a similar suite of habitual manual activities as in later Homo. In contrast, A. africanus and A. afarensis display a mosaic entheseal pattern that combines indications of both humanlike and apelike manipulation. Overall, these findings provide new evidence that some australopith species were already habitually engaging in humanlike manipulation, even if their manual dexterity was likely not as high as in later Homo.

The phylogenetic relationships of the small-bodied catarrhine Pliobates cataloniae (∼11.6 Ma, NE Iberian Peninsula) have been controversial since its original description. However, the recent report of additional dentognathic remains has supported its crouzeliid pliopithecoid status. Based on the available hypodigm, the molar enamel-dentine junction (EDJ) shape of P. cataloniae is compared with that of other pliopithecoids from the same basin as well as both extinct and extant hominoids to further evaluate its pliopithecoid affinities. We also quantitatively compare the EDJ shape among these taxa by means of landmark-based three-dimensional geometric morphometrics using principal component analysis (PCA), canonical variate analysis, and between-group PCA. Permutation tests are performed to test whether Pliobates variation exceeds that of extant hominoid genera. Results indicate that Pliobates is similar in molar EDJ shape to other pliopithecoids, particularly crouzeliids. The variation displayed by Pliobates upper molars is less marked at the EDJ level than at the outer enamel surface, probably owing to differential enamel wear and intraspecific differences in enamel thickness. Multivariate analyses of EDJ shape show that all pliopithecoids (including Pliobates) cluster together in the PCAs, canonical variate analyses, and between-group PCAs and occupy a different portion of the morphospaces from extinct and extant hominoids. Posterior and typicality probabilities strongly support the classification of Pliobates as a pliopithecoid, wheras permutation tests fail to reject the single-genus hypothesis for the P. cataloniae hypodigm. We conclude that P. cataloniae is a crouzeliid pliopithecoid, as recently supported by cladistic analyses of craniodental characters, and that previous cladistic results that supported a stem hominoid status are attributable to postcranial convergences with crown hominoids. Our results further highlight the potential of three-dimensional geometric morphometrics analyses of the EDJ shape for better informing fossil primate alpha-taxonomy by means of quantitatively testing hypotheses about tooth shape variation.

Understanding the mechanism underlying the evolution of knuckle-walking in African great apes but not in humans may provide important implications about the origin and evolution of human bipedal locomotion. In this study, aiming to reveal possible structural adaptations of the chimpanzee's forearm and hand musculature related to knuckle-walking, we measure the passive elastic moment of the chimpanzee's and orangutan's wrist as it was rotated into extension, immobilizing the metacarpophalangeal joint at three different positions: extended (as in knuckle-walking), flexed (as in fist-walking), and an intermediate position. Our findings demonstrate that when the metacarpophalangeal joints are extended, the rigidity of the wrist joint in the extended direction increases. This increased rigidity is attributed to the passive elongation and force generation of digital flexor muscles, which are relatively short in chimpanzees. Consequently, this enhanced wrist-joint rigidity contributes to the stability and energetically efficient transmission of propulsive force to the ground during the stance phase. Overall, our study supports the hypothesis that knuckle-walking is an adaptation to terrestrial locomotion for an ancestor characterized by the restricted capacity for wrist extension owing to the relatively shorter tendons of digital flexor muscles.

The earliest evidence for complex tool use in the archaeological record dates to 3.3 Ma. While wooden tools may have been used by our earliest ancestors, the evidence is absent due to poor preservation. However, insights into possible early hominin wooden tool use can be gained from observing the tool-use practices of our closest living relatives, chimpanzees (Pan troglodytes). By using stone hammers used to crack various nuts, chimpanzees leave a durable material signature comprised of formal tools and associated diagnostic fragments. While the archaeological evidence of chimpanzee wooden tool use is temporary, the combination of stone hammers and wooden anvils can create a more enduring lithic record. This study explores the lithic assemblages associated with wooden and stone anvil use at nut-cracking sites in Taï National Park, Côte d'Ivoire, using technological and use-wear analyses. Our results indicate clear differences in density, fracture patterns, and use-wear in the lithic records between wooden anvil and stone anvil sites. New archaeological excavations at six chimpanzee nut-cracking sites reveal that the anvils' material directly influences the visibility of nut-cracking evidence in the archaeological record. By examining the nature of the lithic signatures associated with wooden anvil and stone anvil use by chimpanzees, we can formulate hypotheses about the probability of such behaviors being preserved and identifiable in the Plio-Pleistocene hominin archaeological record. The variability in material signatures from nut-cracking on different anvils suggests that stone anvils leave a clear archaeological record. Evidence for wooden anvil use is likely underrepresented due to the more ephemeral nature of the associated percussive damage and material signature. It may, however, still be possible, albeit challenging, to identify wooden anvil use in the archaeological record.

Thermoregulation is argued to be an important factor influencing body breadth in hominins based on the relationship of surface area to body mass first proposed by Bergmann. Selection for a narrow thorax, and thus a narrow pelvis, increases body surface area relative to body mass, which could be beneficial in hot climates if it leads to a decrease in core body temperature. However, the relationship between pelvic breadth and thermoregulation in humans has not been established. Although previous work has shown that bi-iliac breadth is significantly positively associated with latitude in humans, we lack an understanding of whether this association is due to climate-related selection, neutral evolutionary processes, or other selective pressures. A missing piece of the puzzle is whether body breadth at the iliac blades is an important factor in thermoregulation. Here, we examine this in a mixed-sex sample of 28 adult runners who ran for one hour at 3.14 m s in a variety of climatic conditions while their core body temperatures were measured using internal temperature sensors. The association of maximum core temperature with anthropometric and demographic variables such as age, sex, mass, body fat percentage, and bi-iliac breadth was analyzed using a linear mixed-effect model. Due to the small sample size, the model was also bootstrapped. We found that an increase in absolute bi-iliac breadth was significantly associated with an increase in maximum core temperature. Overall, this preliminary analysis suggests a link between variation in bi-iliac breadth and maximum core body temperature during running, but further investigation is needed.

Hominoids exhibit a strikingly diverse set of locomotor adaptations-including knuckle-walking, brachiation, quadrumanuous suspension, and striding bipedalism-while also possessing morphologies associated with forelimb suspension. It has been suggested that changes in limb element integration facilitated the evolution of diverse locomotor modes by reducing covariation between serial homologs and allowing the evolution of a greater diversity of limb lengths. Here, I compare limb element integration in hominoids with that of other primate taxa, including two that have converged with them in forelimb morphology, Ateles and Pygathrix. Ateles is part of a clade that, such as hominoids, exhibits diverse locomotor adaptations, whereas Pygathrix is an anomaly in a much more homogeneous (in terms of locomotor adaptations) clade. I find that all atelines (and possibly all atelids), not just Ateles, share reduced limb element integration with hominoids. Pygathrix does not, however, instead resembling other members of its own family. Indriids also seem to have higher limb integration than apes, despite using their forelimbs and hindlimbs in divergent ways, although there is more uncertainty in this group due to poor sample size. These results suggest that reduced limb integration is characteristic of certain taxonomic groups with high locomotor diversity rather than taxa with specific, specialized locomotor adaptations. This is consistent with the hypothesis that reduced integration serves to open new areas of morphospace to those clades while suggesting that derived locomotion with divergent demands on limbs is not necessarily associated with reduced limb integration.

The foragers of the southern African Middle Stone Age were among the first humans to adapt their environment and its resources to their needs. They heat-treated stone to alter its mechanical properties, transformed yellow colorants into red pigments and produced moldable adhesive substances from plants. Until now, only Podocarpus conifers have been identified as the botanical origin of Middle Stone Age adhesives. This is curious as these conifers do not produce sticky exudations that could be recognized as potential adhesives. To obtain an adhesive, tar must be made with a technical process based on fire. However, the nature of these technical processes has remained unknown, hampering our understanding of the meaning of this adhesive technology for the cultural evolution of early Homo sapiens. Here, we present the first evidence of a technique used for tar making in the Middle Stone Age. We created an experimental reference collection containing naturally available adhesives along manufactured tars from plants available in the Middle Stone Age and compared these to artifacts using gas chromatography-mass spectrometry and infrared spectroscopy. We found that, in the Howiesons Poort at Sibhudu Cave, tar was made by condensation, an efficient above-ground process. Even more surprisingly, the condensation method was not restricted to Podocarpus. The inhabitants of Sibhudu also produced tar from the leaves of other plants. These tars were then used, either without further transformation or were processed into ochre-based compound adhesives, suggesting that people needed different moldable substances with distinct mechanical properties. This has important implications for our understanding of Middle Stone Age H. sapiens, portraying them as skilled engineers who used and transformed their resources in a knowledgeable way.

A hominin mandible, KNM-ER 63000, and associated vertebrate remains were recovered in 2011 from Area 40 in East Turkana, Kenya. Tephrostratigraphic and magnetostratigraphic analyses indicate that these fossils date to ∼4.3 Ma. KNM-ER 63000 consists of articulating but worn and weathered mandibular corpora, with a broken right M crown and alveoli preserved at other tooth positions. Despite extensive damage, KNM-ER 63000 preserves diagnostic anatomy permitting attribution to Australopithecus anamensis. It can be distinguished from Australopithecus afarensis by its strongly inclined symphyseal axis with a basally convex, 'cut-away' external surface, a lateral corpus that sweeps inferomedially beneath the canine-premolar row, and alignment of the canine alveolus with the postcanine axis. KNM-ER 63000 is distinguished from Ardipithecus ramidus by its thick mandibular corpus and large M crown. The functional trait structure and enamel's stable carbon isotopic composition of the Area 40 large-mammal community suggests an environment comparable to Kanapoi and other ∼4.5-4 Ma eastern African sites that would have offered Au. anamensis access to both C and C food resources. With an age of ∼4.3 Ma, KNM-ER 63000 is the oldest known specimen of Au. anamensis, predating the Kanapoi and Asa Issie samples by at least ∼100 kyr. This specimen extends the known temporal range of Au. anamensis and places it in temporal overlap with fossils of Ar. ramidus from Gona, Ethiopia. The morphology of KNM-ER 63000 indicates that the reconfigured masticatory system differentiating basal hominins from the earliest australopiths existed in the narrow temporal window, if any, separating the two. The very close temporal juxtaposition of these significant morphological and adaptive differences implies that Ar. ramidus was a relative rather than a direct phyletic ancestor of earliest Australopithecus.

Zooarcheological and geochemical evidence suggests Neanderthals were top predators, but their adherence to a strictly carnivorous diet has been questioned. Recent studies have demonstrated the potential of calcium-stable isotopes to evaluate trophic and ecological relationships. Here, we measure the δCa values in bone samples from Mousterian contexts at Grotte du Bison (Marine Isotope Stage 3, Yonne, France) and Regourdou (Marine Isotope Stage 5, Dordogne, France) in two new Neanderthal individuals, associated fauna, and living local plants. We use a Bayesian mixing model to estimate the dietary composition of these Neanderthal individuals, plus a third one already analyzed. The results reveal three distinct diets: a diet including accidental or voluntary consumption of bone-based food, an intermediate diet, and a diet without consumption of bone-based food. This finding is the first demonstration of diverse subsistence strategies among Neanderthals and as such, reconciles archaeological and geochemical dietary evidence.

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.