Do rates of dental wear in extant African great apes inform the time of weaning?

Reconstructing the life histories of extinct hominins remains one of the main foci of paleoanthropological inquiry, as an extended juvenile period impacts the social and cognitive development of species. However, the paucity of hominin remains, the lack of comparative hominoid data, and the destructive nature of many life history approaches have limited our understanding of the relationship between dental development (eruption) and weaning in primates. Alternatively, the rate of dental wear in early-forming teeth has been suggested a good proxy for the timing of weaning. Here we test this hypothesis on an ontogenetic series of Gorilla gorilla gorilla and Pan troglodytes troglodytes, using geographic information systems-based shape descriptors of M1s in relation to the nitrogen (δ15N) and carbon (δ13C) isotope composition of their associated hair. Results show that Gorilla g. gorilla are fully weaned considerably later than Pan t. troglodytes, that is, after M1s had been in full functional occlusion for some time. Yet, throughout ontogeny, gorilla dental wear rates are greater than they are in chimpanzees. This refutes the hypothesis that the rates of wear of early-forming teeth inform the time of weaning (i.e., nutritional independence). Instead, dietary breadth and seasonal variation in resource availability are implicated. This finding has implications for interpreting the hominin fossil record and raises questions about the triggers for, and the mechanisms of, life history change in hominin evolution. As a case in point, commonalities in life history patterns between early hominins and Western lowland gorillas seem to be a means to mitigate the effects of recurrent (i.e., seasonal) resource limitations and-conceivably-to prevent high infant mortality rates. Taken further, difference between hominid life histories are likely to be of degree, not kind.

Age-related tooth wear in African rainforest hunter-gatherers.

OBJECTIVES: Central African small-scale foragers subsist primarily on hunting game activities and wild plant-food gathering. Starch-rich tubers are underground storage organs (USOs) and staple food resources in savanna and tropical rainforests. However, little is known about the effect of USO consumption on tooth wear development in living hunter-gatherers. We report age- and sex-dependent tooth wear rates in forest-dwelling Baka Pygmies with well-documented wild-yam-tuber-based diet to explore the long-term impact of USO mechanical hardness and abrasiveness on the wearing down of the teeth. MATERIALS AND METHODS: Percentages of dentine exposure (PDEs) of permanent left mandibular first molars (M1 ) were recorded using in vivo high-resolution replicas of Baka individuals (aged 8-33 years), inhabiting Le Bosquet district in Cameroon (Western Africa). Regression and covariance analyses were used to test the effect of individual aging by sex on PDE rates. RESULTS: We found a strong increase of PDE by age among Baka individuals. No evidence of sexual dimorphism in wear patterns suggests similar sex-related dietary and masticatory demands during growth. Overall, greatest dentine exposure values ≈4% denote unexpected slow wear down rates for foraging diets relying on USO consumption. DISCUSSION: The low molar wear rates with age found in Baka Pygmies contrast with extensive wear rates in savanna-dwelling foragers, reflecting differences in thermal processing techniques affecting fracture toughness and grittiness of mechanically challenging foods. Our findings reveal that culture-specific dietary proclivities influence tooth wear among foraging behaviors with important implications in hominin dietary versatility and abrasive stress on chewing surfaces.

Dental size variability in Central African Pygmy hunter-gatherers and Bantu-speaking farmers.

OBJECTIVES: Odontometric studies of African populations show high within-group variation in tooth size. Overall, North Africans exhibit smaller dimensions than groups from eastern and southern sub-Saharan regions, but no previous studies have analyzed the full dental metrics among extant African Pygmy hunter-gatherers and Bantu-speaking farmers. Furthermore, the population variability in tooth crown sizes from equatorial rainforest regions remains to be elucidated. MATERIALS AND METHODS: The mesiodistal and buccolingual diameters of the permanent teeth (I1-M2) were measured in vivo using high-resolution replicas from Baka Pygmies and Mvae and Yassa Bantu-speakers from Cameroon (western Africa). Analyses of variance were used to record sex-related and population-level differences in tooth sizes, and a principal component analysis of geometrically scaled measures was used to plot the odontometric variability among groups. RESULTS: Cameroonian Baka Pygmies differ in dental size from their Bantu-speaking neighbors. Molar teeth are larger in Pygmies than in Bantu individuals, while the anterior dentition is larger in the Bantu. Baka males exhibit significantly larger teeth than females, whereas sexual dimorphism in non-Pygmies is only present in the anterior dentition. DISCUSSION: Odontometric patterns and the degree of sexual dimorphism in dental size differ among Central African groups, indicating adaptation to their different forager and farmer lifestyles. In particular, the admixture of Bantu-speakers in Baka populations is smaller than that in other western Pygmy groups. The greater dental phenetic diversity in Baka compared to that of the smaller-toothed farmers suggests that ecogenetic and microevolutionary factors are influencing a particular divergence scenario.

Anterior dental microwear textures show habitat-driven variability in Neandertal behavior.

The causes of Neandertal anterior tooth wear patterns, including labial rounding, labial scratches, and differential anterior-posterior wear, have been debated for decades. The most common explanation is the "stuff-and-cut" hypothesis, which describes Neandertals clamping down on a piece of meat and slicing a portion close to their lips. "Stuff-and-cut" has been accepted as a general aspect of Neandertal behavior without fully assessing its variability. This study analyzes anterior dental microwear textures across habitats, locations, and time intervals to discern possible variation in Neandertal anterior tooth-use behavior. Forty-five Neandertals from 24 sites were analyzed, represented by high-resolution replicas of permanent anterior teeth. The labial surface was scanned for antemortem microwear using a white-light confocal profiler. The resultant 3D-point clouds, representing 204 × 276 µm for each specimen, were uploaded into SSFA software packages for texture characterization. Statistical analyses, including MANOVAs, ANOVAs, and pairwise comparisons, were completed on ranked microwear data. Neandertal descriptive statistics were also compared to 10 bioarchaeological samples of known or inferred dietary and behavioral regimes. The Neandertal sample varied significantly by habitat, suggesting this factor was a principal driving force for differences in Neandertal anterior tooth-use behaviors. The Neandertals from open habitats showed significantly lower anisotropy and higher textural fill volume than those inhabiting more closed, forested environments. The texture signature from the open-habitat Neandertals was most similar to that of the Ipiutak and Nunavut, who used their anterior teeth for intense clamping and grasping behaviors related to hide preparation. Those in more closed habitats were most similar to the Arikara, who did not participate in non-dietary behaviors. These Neandertal individuals had a broad range of texture values consistent with non-dietary and dietary behaviors, suggesting they varied more in anterior tooth-use behaviors and exploited a wider variety of plant and animal resources than did those from open habitats.

Buccal dental microwear texture and catarrhine diets.

OBJECTIVES: Two-dimensional dental microwear analyses on occlusal and nonocclusal enamel surfaces have been widely applied to reconstruct the feeding behaviors of extant primates and to infer ecological adaptations in fossil hominins. To date, analyses of dental microwear texture, using three-dimensional, Scale-Sensitive Fractal Analysis approaches has only been applied to occlusal surfaces. Here, for the first time, we apply this 3D proxy to buccal enamel surfaces of catarrhine primates of known feeding ecologies to assess the utility of nonocclusal microwear texture variables as indicators of dietary habits. MATERIALS AND METHODS: Buccal microwear texture attributes were collected from high-resolution second molar casts in a sample of seven extant African catarrhine taxa with differing dietary behaviors. A white-light confocal microscope with a 100× objective lens was used to record six microwear texture variables that assess complexity, anisotropy, heterogeneity, and textural fill volume. RESULTS: The physical properties and variation in hardness of ingested foods is reflected by significant differences in the microwear variables on buccal enamel surfaces between species, which is in agreement with early reports using 2D microwear signatures of the same samples. Species that consume hard brittle items showed high buccal enamel complexity and low anisotropy values, while folivorous species that consume tough foods revealed high anisotropy and low complexity enamel patterns. DISCUSSION: Buccal microwear texture analysis on enamel surfaces clearly reflects diet-related variation in nonhuman primates. Our findings indicate that microwear texture attributes on nonworking enamel surfaces provide an alternative procedure for reconstructing dietary behavior when wear facets on occlusal surfaces are lacking.

Ancient DNA analysis of 8000 B.C. near eastern farmers supports an early neolithic pioneer maritime colonization of Mainland Europe through Cyprus and the Aegean Islands.

The genetic impact associated to the Neolithic spread in Europe has been widely debated over the last 20 years. Within this context, ancient DNA studies have provided a more reliable picture by directly analyzing the protagonist populations at different regions in Europe. However, the lack of available data from the original Near Eastern farmers has limited the achieved conclusions, preventing the formulation of continental models of Neolithic expansion. Here we address this issue by presenting mitochondrial DNA data of the original Near-Eastern Neolithic communities with the aim of providing the adequate background for the interpretation of Neolithic genetic data from European samples. Sixty-three skeletons from the Pre Pottery Neolithic B (PPNB) sites of Tell Halula, Tell Ramad and Dja'de El Mughara dating between 8,700-6,600 cal. B.C. were analyzed, and 15 validated mitochondrial DNA profiles were recovered. In order to estimate the demographic contribution of the first farmers to both Central European and Western Mediterranean Neolithic cultures, haplotype and haplogroup diversities in the PPNB sample were compared using phylogeographic and population genetic analyses to available ancient DNA data from human remains belonging to the Linearbandkeramik-Alföldi Vonaldiszes Kerámia and Cardial/Epicardial cultures. We also searched for possible signatures of the original Neolithic expansion over the modern Near Eastern and South European genetic pools, and tried to infer possible routes of expansion by comparing the obtained results to a database of 60 modern populations from both regions. Comparisons performed among the 3 ancient datasets allowed us to identify K and N-derived mitochondrial DNA haplogroups as potential markers of the Neolithic expansion, whose genetic signature would have reached both the Iberian coasts and the Central European plain. Moreover, the observed genetic affinities between the PPNB samples and the modern populations of Cyprus and Crete seem to suggest that the Neolithic was first introduced into Europe through pioneer seafaring colonization.

Quantification of Myosin Heavy Chain Isoform mRNA Transcripts in the Supraspinatus Muscle of Vertical Clinger Primates.

Vertical clinging is a specialized form of locomotion characteristic of the primate family Callitrichidae. Vertical clinging requires these pronograde primates to maintain a vertical posture, so the protraction of their forelimbs must resist gravity. Since pronograde primates usually move as horizontal quadrupeds, we hypothesized that the supraspinatus muscle of vertical clingers would present specific characteristics related to the functional requirements imposed on the shoulder area by vertical clinging. To test this hypothesis, we quantified by real-time quantitative polymerase chain reaction the mRNA transcripts of myosin heavy chain (MHC) isoforms in the supraspinatus muscle of 15 species of pronograde primates, including vertical clingers. Our results indicate that the supraspinatus of vertical clingers has a specific expression pattern of the MHC isoforms, with a low expression of the transcripts of the slow MHC-I isoform and a high expression of the transcripts of the fast MHC-II isoforms. We conclude that these differences can be related to the particular functional characteristics of the shoulder in vertical clingers, but also to other anatomical adaptations of these primates, such as their small body size.

Molar shape variability in platyrrhine primates.

Recent phylogenetic analyses suggest that platyrrhines constitute a monophyletic group represented by three families: Cebidae, Atelidae, and Pitheciidae. Morphological variability between and within these three families, however, is widely discussed and debated. The aim of this study was to assess molar shape variability in platyrrhines, to explore patterns of interspecific variation among extant species, and to evaluate how molar shape can be used as a taxonomic indicator. The analyses were conducted using standard multivariate analyses of geometric morphometric data from 802 platyrrhine lower molars. The results indicated that the interspecific variation exhibited a highly homoplastic pattern related to functional adaptation of some taxa. However, phylogeny was also an important factor in shaping molar morphological traits, given that some phenotypic similarities were consistent with current phylogenetic positions. Our results show that the phylogenetic and functional signals of lower molar shape vary depending on the taxa and the tooth considered. Based on molar shape, Aotus showed closer similarities to Callicebus, as well as to some Cebidae and Ateles-Lagothrix, due to convergent evolutionary trends caused by similar dietary habits, or due to fast-evolving branches in the Aotus lineage, somewhat similar to the shape of Callicebus and Cebidae.

Phylogenetic signal in molar dental shape of extant and fossil catarrhine primates.

Morphology has been widely used for inferring the phylogenies of numerous taxonomic groups. Recent molecular studies performed on extant non-human primates, however, have cast doubt on the reliability of cranial and postcranial characters for characterizing evolutionary affinities. Because molecular evidence is often not available for fossil specimens, detecting phylogenetic signals in anatomical features is of great relevance. Here we have analyzed molar (M1 and M2) crown shape by means of geometric morphometrics in a large sample of both extant and fossil Miocene catarrhine primates to detect the phylogenetic signal in molar morphometry. Results support that molar shape carries a strong phylogenetic signal, mostly at the superfamily level but also to some extent at the family level. Dietary factors, however, appear to have less influence, especially for M2. The Miocene Pliopithecoidea, Cercopithecoidea, and Hominoidea superfamilies clearly grouped according to the expected taxonomic affinities with the extant groups, although some discrepancies were found depending on the tooth considered. Our findings suggest that although molar crown shape can be used as a reliable proxy for establishing taxonomic affinities of catarrhine fossil primates with extant groups, a significant amount of interspecific variation exists, indicative of derived adaptations at the genus or species level.

OH-65: The earliest evidence for right-handedness in the fossil record.

Labial striations on the anterior teeth have been documented in numerous European pre-Neandertal and Neandertal fossils and serve as evidence for handedness. OH-65, dated at 1.8 mya, shows a concentration of oblique striations on, especially, the left I1 and right I1, I2 and C1, which signal that it was right-handed. From these patterns we contend that OH-65 was habitually using the right hand, over the left, in manipulating objects during some kind of oral processing. In living humans right-handedness is generally correlated with brain lateralization, although the strength of the association is questioned by some. We propose that as more specimens are found, right-handedness, as seen in living Homo, will most probably be typical of these early hominins.

Morphological affinities of the proximal humerus of Epipliopithecus vindobonensis and Pliopithecus antiquus: suspensory inferences based on a 3D geometric morphometrics approach.

Suspension plays a major adaptive role in shaping primate postcranial morphology, which therefore enables this positional behavior to be inferred in extinct taxa. The proximal humerus stands as a key region for inferring forelimb suspensory capabilities because its morphology can be effectively linked, from a functional viewpoint, to differences in suspension use between primate taxa. Here we provide an assessment of the suspensory capabilities of two pliopithecoids (Epipliopithecus vindobonensis and Pliopithecus antiquus) by means of a 3D geometric morphometric analysis of proximal humeral shape. The comparative sample includes proximal humeri from eight extant anthropoid genera, as well as other extinct catarrhines (the propliopithecoid Aegyptopithecus zeuxis, the stem hominoid Nyanzapithecus vancouveringorum, and an unascribed small catarrhine, GSP 28062, from the Middle Miocene of Pakistan). Body mass estimates based on allometric regressions of humeral head superoinferior diameter are also provided. Our results support some degree of forelimb suspensory behaviors for Epipliopithecus and GSP 28062. In contrast, and unlike previous qualitative assessments, our analysis shows that P. antiquus has a distinct glenohumeral morphology, much closer to that displayed by generalized arboreal quadrupeds with no evidence of suspensory adaptations (as in Aegyptopithecus and stem hominoids from Africa).

Shape analysis of the proximal humerus in orthograde and semi-orthograde primates: correlates of suspensory behavior.

"Suspensory locomotion" is an expression that encompasses a series of specialized forms of locomotion that mainly orthograde primates use to achieve below-branch traveling. It implies a number of features in the entire body associated with the use of the forelimb in overhead positions. The glenohumeral joint is one of the main joints involved in effective suspensory locomotion, being subject to a delicate balance between the high degree of mobility and stabilization needed to successfully engage in suspensory behaviors. Here, we present a 3D geometric morphometric study that explores the form of the proximal humerus of six orthograde and semi-orthograde genera (Hylobates, Pongo, Pan, Gorilla, Ateles, and Lagothrix) and a pronograde genus, Colobus, to determine to what extent suspensory locomotor requirements are driving the shape of this epiphysis. Results show the presence of a morphocline related to degree of suspension in the shape of the articular surface, with highly suspensory taxa (i.e., Hylobates) exhibiting particular morphological traits at the articular surface that provide a greater range of circumduction. The placement and orientation of the rotator cuff muscles' insertion sites on the tubercles appear associated with the divergent forces operating at the joint in quadrupedal or above-head use of the hand.

Brief communication: Developmental versus functional three-dimensional geometric morphometric-based modularity of the human proximal humerus.

The proximal humerus is formed by three secondary ossification centers during the postnatal trajectory of the human infant. The ossification centers later grow into the structures of the articular surface, major tubercle, and minor tubercle. There is a purported functional division between the articular surface and the tubercles, with the articular surface mainly responsible for the range of movement of the shoulder joint, and the tubercles bearing the insertions of the rotator cuff muscles, mainly devoted to securing the joint against humeral displacement. Using three-dimensional geometric morphometrics, we tested the presence of such developmental and functional divisions in the proximal humerus, applying the RV coefficient of Escoufier to these a priori hypothesized modules. Our results indicate that the proximal humerus might be a generally integrated structure. However, a weak signal for modular configuration was present, with slightly stronger support for the two modules depicting the boundaries between the purported functional regions of the epiphysis: the articular surface and the tubercles.

Dental shape variability in cercopithecoid primates: a model for the taxonomic attribution of macaques from Roman archaeological contexts.

Morphometric variation of biological structures has been widely used to determine taxonomic affinities among taxa, and teeth are especially informative for both deep phylogenetic relationships and specific ecological signals. We report 2-dimensional geometric morphometrics (GM) analyses of occlusal crown surfaces of lower molars (M1, n = 141; M2, n = 158) of cercopithecoid primate species. A 12-landmark configuration, including cusp tips and 8 points of the molar crown contour, were used to evaluate patterns of variation in lower molar shape among cercopithecoid primates and to predict the taxonomic attribution of 2 archaeological macaques from Roman time periods. The results showed that the lower molar shape of cercopithecoid primates reflects taxonomic affinities, mostly at a subfamily level and close to a tribe level. Thus, the cusp positions and crown contour were important elements of the pattern related to interspecific variation. Additionally, the archaeological specimens, attributed to Macaca sylvanus based on osteological information, were classified using the GM molar shape variability of the cercopithecoid primates studied. The results suggest that their molar shape resembled both M. sylvanus and M. nemestrina, and species attribution varied depending on the comparative sample used.

Exploring the interplay of bone lesions: unraveling health implications and daily life challenges in an Iron Age skeleton from Ya'amun, Jordan.

This study analyzed the paleopathological conditions of a 30-year-old male unearthed at the site of Ya'amun in northern Jordan. The skeleton was dated back to Iron age. The paleopathological examinations were performed using macroscopic and radiological analyses. The results revealed multiple significant bone lesions, including periosteal osteosarcoma of the right femur, plagiocephaly, asymmetry of the sacrum, vertebral fractures, anemia, and osteoarthritis. This case represents the first example of neoplasm and plagiocephaly in the Iron Age of the region. Despite enduring severe health conditions, the individual managed to reach the third decade while facing the demands of strenuous daily activities that exemplified the harsh living and subsistence conditions characteristic of the Iron Age.

Brief communication: Morphological effects of captivity: A geometric morphometric analysis of the dorsal side of the scapula in captive-bred and wild-caught Hominoidea.

Many osteological collections from museums and research institutions consist mainly of remains from captive-bred animals. The restrictions related to the space of their enclosures and the nature of its substrate are likely to affect the locomotor and postural behaviors of captive-bred animals, which are widely considered uninformative regarding bone morphology and anatomical adaptations of wild animals, especially so in the case of extant great apes. We made a landmark-based geometric morphometrics analysis of the dorsal side of the scapular bone of both wild-caught and captive-bred great apes to clarify the effect of captivity on the morphology of a bone greatly involved in locomotion. The comparison suggested that captivity did not have a significant effect on the landmark configuration used, neither on average scapular shape nor shape variability, being impossible to distinguish the scapulae of a captive-bred animal from that of a wild-caught one. This indicates that the analyzed scapulae from captive Hominoidea specimens may be used in morphological or taxonomic analyses since they show no atypical morphological traits caused by living conditions in captivity.

3D geometric morphometric analysis of the proximal epiphysis of the hominoid humerus.

In this study we perform a three-dimensional geometric morphometric (3D GM) analysis of the proximal epiphysis of the humerus in extant great apes, including humans, in order to accurately describe the functional anatomical differences between these taxa. In addition, a fossil hominin specimen of Australopithecus afarensis was included in a multivariate GM analysis in order to test the potential of this methodological approach for making locomotor inferences from fossil remains. The results obtained show significant differences in proximal humeral morphology among the taxa studied, which had thus far largely remained unnoticed. Based on morphofunctional considerations, these anatomical differences can be correlated to differences in the locomotor repertoires of the taxa, thus confirming that the proximal humerus is suitable for constructing paleobiological inferences about locomotion. Modern humans display markedly divergent features, which set them apart from both the extant great apes and the fossil hominin A. afarensis. The morphology of the proximal epiphysis of the humerus of the latter more closely resembles that of the orangutans, thus suggesting that despite hindlimb adaptations to bipedalism, the forelimb of this taxon was still functionally involved in arboreal behaviors, such as climbing or suspension.

Brief communication: Short- and long-term in vivo human buccal-dental microwear turnover.

Buccal-dental microwear depends on the abrasive content of chewed foodstuffs and can reveal long-term dietary trends in human populations. However, in vivo experimental analyses of buccal microwear formation processes are scarce. Here, we report the effects of an abrasive diet on microwear rates in two adult volunteers at intervals of 8 days over a period of 1 month and document long-term turnover over 5 consecutive years in the same subjects under an ad libitum Mediterranean diet. Buccal microwear was analyzed on mandibular first molars using high-resolution replicas and scanning electron microscopy. Microwear turnover was assessed by recording the scratches lost and gained at each time point. Our results indicate that scratch formation on enamel surfaces increased with a highly abrasive diet compared to both pre-test and post-test ad libitum dietary controls. In the long-term analysis, scratch turnover was higher than expected, but no significant long-term trends in microwear density or length were observed, because microwear formation was compensated by scratch disappearance. Our results confirm that buccal microwear patterns on mandibular molars show a dynamic formation process directly related to the chewing of abrasive particles along with ingested food. In addition, the observed long-term stability of buccal microwear patterns makes them a reliable indicator of overall dietary habits.

Age and individual foraging behavior predict tooth wear in Amboseli baboons.

Teeth represent an essential component of the foraging apparatus for any mammal, and tooth wear can have significant implications for survival and reproduction. This study focuses on tooth wear in wild baboons in Amboseli, southern Kenya. We obtained mandibular and maxillary tooth impressions from 95 baboons and analyzed digital images of replicas made from these impressions. We measured tooth wear as the percent dentine exposure (PDE, the percent of the occlusal surface on which dentine was exposed), and we examined the relationship of PDE to age, behavior, and life history variables. We found that PDE increased significantly with age for both sexes in all three molar types. In females, we also tested the hypotheses that long-term patterns of feeding behavior, social dominance rank, and one measure of maternal investment (the cumulative number of months that a female had dependent infants during her lifetime) would predict tooth wear when we controlled for age. The hypothesis that feeding behavior predicted tooth wear was supported. The percent of feeding time spent consuming grass corms predicted PDE when controlling for age. However, PDE was not associated with social dominance rank or maternal investment.

Late neandertals in southeastern Iberia: Sima de las Palomas del Cabezo Gordo, Murcia, Spain.

Middle Paleolithic fossil human remains from the Sima de las Palomas in southeastern Iberia (dated to