OBJECTIVES:Ontogenetic trajectories in intrinsic hand and foot proportions are likely to vary in primates according to their locomotor adaptations. We analyzed the developmental trajectories of chimpanzees (Pan troglodytes), which exhibit particular locomotor adaptations related to suspensory and climbing abilities, testing whether autopodial growth reflects biomechanical and ecological constraints associated with ontogenetic changes in locomotor behavior. MATERIALS AND METHODS:We analyzed 157 radiographs of 7 female and 198 of 8 male P. troglodytes individuals, from 1.5 to 13 years old. Lengths of metapodials and proximal/intermediate phalanges were measured to compute phalangeal indices (PIs: ratio of summed non-distal phalangeal length to corresponding metapodial length). Ontogenetic allometry was assessed by regressing bone length against body mass, with sex included as a factor. Non-linear Gompertz growth models were fitted to estimate bone-specific growth rates and durations. RESULTS:The results show a positively allometric relationship between all bone lengths and body mass. However, sex-related differences are observed in the allometry of phalanges and metapodials. PIs decline during growth for all digits, with this ontogenetic decline remaining highly similar between sexes. Gompertz models further indicate distinct growth rates between manual and pedal elements. DISCUSSION:Ontogenetic changes in chimpanzees indicate canalized autopodial growth, with reduced intrinsic proportional changes at ~5 years, aligning with their major positional shift. Comparative analyses show species-specific phalangeal trajectories, possibly more pronounced in the foot than in the hand and likely reflecting adaptations to ecological and locomotor demands, such as terrestrial knuckle-walking in large-bodied chimpanzees.
OBJECTIVES:Childbirth complications occur if fetal size is excessive for the maternal birth canal. We hypothesized that young women's metabolic traits (organ and muscle mass, resting energy expenditure (REE)) known to promote fetal growth would correlate with dimensions of the birth canal, and that some of this association would be explained by growth markers (tibia length, height). MATERIALS AND METHODS:We analyzed cross-sectional data on anthropometry, organ mass (magnetic resonance imaging (MRI)), skeletal muscle (dual-energy X-ray absorptiometry), fat mass (4-component model), pelvic dimensions (MRI), and REE (indirect calorimetry) in 68 nulliparous women aged 20-28 years of South Asian ancestry living in the UK. Principal component analysis (PCA) was used to summarize variability in organ/muscle mass and pelvic dimensions (PCApelvis). Associations between metabolic and pelvic traits were assessed using Pearson correlations, and partial correlations adjusting for height or tibia length. RESULTS:Mean height was 161 cm and body mass index 22.3 kg/m2. There were positive correlations between REE, organ/muscle mass, head girth and the first PCApelvis score, which were partly explained by variability in tibia and height. Fat mass was associated with REE and organ/muscle mass but not pelvic dimensions. DISCUSSION:Correlations between metabolic and pelvic traits indicate a degree of coordination: women with greater metabolic capacity to promote fetal growth also have larger pelvic dimensions, partly explained by linear growth patterns. However, body fat in nulliparous women correlates with REE but not pelvic dimensions; hence high adiposity could increase risk of childbirth complications when these women give birth.
OBJECTIVES:Metagenomic investigations of ancient dental calculus provide insights into oral health, disease, and diet. Here, we analyze the dental calculus metagenome of King Richard III of England (1452-1485). MATERIALS AND METHODS:Dental calculus DNA was extracted from three teeth of King Richard III and shotgun sequenced to a depth of nearly 400 million reads. The metagenomic data were taxonomically profiled and compared to new and previously published dental calculus metagenomes from England, Ireland, the Netherlands, and Germany spanning the Neolithic to the present. Sequencing data were de novo assembled, and metagenome-assembled genomes assigned to the genus Tannerella were investigated for phylogenetic relatedness and virulence. Putative dietary DNA was assessed for authenticity. RESULTS:The dental calculus of King Richard III was well-preserved and yielded an exceptionally high quantity of DNA. Oral microbiome species diversity fell within the range previously observed among other northern European populations, suggesting that a royal lifestyle and a rich diet did not substantially impact his oral microbiota. The reconstructed Tannerella genomes contained many virulence factors found today among oral Tannerella species. No putative dietary DNA could be authenticated. DISCUSSION:The dental calculus of King Richard III produced one of the richest ancient oral metagenomes published to date, yet the species diversity was indistinguishable from that of commoners living in northern Europe over the last 7000 years. Insufficient plant and animal DNA were recovered to investigate diet, suggesting that dental calculus may not be a sufficient source of dietary DNA even when exceptionally well-preserved.
OBJECTIVES:This study explores the subsistence strategies of Middle-to-Late Holocene human populations in the Argentinean Pampas and Paraná River Delta by analyzing dental microwear patterns. MATERIALS AND METHODS:We examined occlusal molar microwear textures of individuals from the Middle and Late Holocene recovered from 12 archaeological sites across three ecologically distinct areas: the Upper Delta of the Paraná River, Central Pampas, and the lower Colorado River Valley. RESULTS:Our results reveal both expected and unexpected trends. Individuals from the resource-rich Upper Delta of the Paraná River exhibited the predicted high dietary diversity (indicated by elevated mean heterogeneity (Hasfc81) values) but also showed surprisingly high mean complexity values (Asfc)-exceeding even those from the two semi-arid areas (Central Pampas and lower Colorado River Valley), where environmental abrasives would have been expected to have resulted in greater microwear texture complexity. DISCUSSION:Within the Paraná Delta, significant intra-site variation at Los Tres Cerros 1 suggests differential food access, possibly tied to social stratification in the Goya-Malabrigo archaeological entity. In the Central Pampas, Middle Holocene individuals from the Arroyo Seco 2 archaeological site displayed greater dietary heterogeneity than contemporaneous and Late Holocene sites, contradicting expectations of progressive diversification during this period. These findings underscore that prehistoric subsistence strategies emerged from complex interactions between ecological constraints and cultural practices, including food processing and social organization.
OBJECTIVES:The study of deciduous teeth provides insights into early dental development, morphological variation and underlying biological processes, with relevance to oral biology, pediatric dentistry and anthropological research. Here, we analyze the linear dimensions of the largest known sample of associated deciduous molars to investigate patterns of sexual dimorphism, covariation, and developmental integration. MATERIALS AND METHODS:The sample comes from the Ratón Pérez Collection, a modern human sample curated at the National Research Center on Human Evolution (Burgos, Spain). Standard odontometric measurements were collected from 428 upper and lower deciduous molars from 211 children, including mesiodistal (MD) and buccolingual (BL) diameters, crown index (CI) and crown area (CA). The sample included isolated and associated individuals, enabling within-individual comparisons across teeth and jaws. Statistical analyses evaluated sexual dimorphism and correlation between molars within and across dental arcades. RESULTS:Sexual dimorphism is generally low, with significant differences restricted to a small number of comparisons, mainly involving mandibular second deciduous molars. Within individuals, crown size-related variables (MD, BL, and CA) show strong and consistent metameric covariation (dm1-dm2) and between dental arcades (upper-lower), indicating developmental integration. Crown proportions (CI) display weaker and less consistent associations. DISCUSSION:These findings indicate that crown size during early odontogenesis is shaped by shared developmental influences operating across the deciduous molar field. In contrast, crown proportions reflect localized aspects of crown morphology. The weak expression of sexual dimorphism supports the use of pooled samples, while the strong integration of size-related variables helps explain the effectiveness of odontometric approaches.
OBJECTIVES:We examined how seasonality and reproductive stage affect foraging behavior in adult female white-headed langurs (Trachypithecus leucocephalus). Because high-quality foods (e.g., young leaves and fruits) become scarce in the dry season, forcing langurs to shift to low-quality mature leaves, we predicted females would increase food intake either by extending feeding bout duration or elevating intake rate. Given the high metabolic costs of lactation, we further predicted lactating females would consume more food than non-lactating females, and that maternal intake would change with infant age. METHODS:Data were collected over 14 months from a habituated group of 12 individuals using focal sampling. For each session, an adult female was randomly selected for observation and video recording; if the focal individual was out of sight for > 5 min, we switched to another visible adult. Videos were used to quantify feeding bout duration, food intake, and intake rate. RESULTS:Adult females had significantly higher intake of young leaves in the wet season than in the dry season, whereas intake of fruits was significantly higher in the dry season. Lactating females showed no significant differences from non-lactating females in feeding bout duration and intake rate, but their intake of young leaves was significantly higher. Infant age (months) did not affect maternal feeding bout traits. DISCUSSION:In the karst habitat, langurs maintain energy balance not by increasing overall food intake, but via dietary selectivity (prioritizing young leaves), seasonal dietary switching (exploiting dry season fruits), and a prolonged lactation period that spreads metabolic costs.
Taxonomic practice in evolutionary biology increasingly prioritizes the recognition of monophyletic groups (clades), yet paleoanthropology still applies this principle inconsistently. Here, I outline these inconsistencies and broader challenges in hominin taxonomy and propose a potential solution. Australopithecus is widely considered non-monophyletic. In addition, the temporal depth of Homo is shallow relative to most primate genera, with recently diverged genera often taxonomically unstable due to complex morphological and genetic signatures and extensive gene flow among closely related taxa. The hominin fossil record exhibits pronounced morphological mosaicism and homoplasy, with supposedly key traits increasingly blurred both within and among genera. This obscures putative adaptive distinctions and contributes to persistent taxonomic disagreement. One potential solution is the subsumption of Australopithecus and Paranthropus within an expanded genus Homo. Such a revision would help address problems of non-monophyly, avoid conceptual difficulties associated with genera with shallow time depths, and facilitate more coherent evolutionary comparisons within a more stable taxonomy. Within this framework, Hominini is best defined as the Pan-Homo clade, with Hominina retained as the appropriate subtribal designation for the human clade. Although similar proposals have been advanced previously, accumulating fossil and genetic evidence makes this a timely moment to reconsider hominin taxonomy. This proposal has limitations, including the loss of taxonomic information relating to adaptive and ecological variation, particularly within Paranthropus and large-brained Homo. At a minimum, however, this article argues for greater consistency and transparency in distinguishing clades from grades in homininan taxonomy, and for more consistent criteria for the recognition of genera.
OBJECTIVES:Caregiving during early childhood emerges from a dynamic interplay between maternal and allomaternal contributions. This study aimed to challenge polarized portrayals of hunter-gatherer childcare as either "mother-centered" or "cooperative" and provide empirical evidence for an integrative cross-cultural approach. MATERIALS AND METHODS:We compared caregiving structures in two hunter-gatherer populations positioned at contrasting ends of a continuum of child-rearing strategies: the !Xun in southern Africa, portrayed as emphasizing mother-child closeness, and the Baka in central Africa, described as exemplifying cooperative caregiving. Over 500 h of caregiving interactions involving 40 children (1-59 months) were recorded using a standardized focal-follow protocol with 30-s interval coding. Rates of maternal, allomaternal, and peer-based caregiving behaviors were analyzed using generalized additive mixed models. RESULTS:Maternal holding did not differ between the !Xun and the Baka, underscoring the central role of mothers during infancy. However, breastfeeding was less frequent among the !Xun than among the Baka. Allomaternal holding was less frequent among the !Xun than among the Baka. When focusing on child and adolescent allomaternal caregivers, child-holding was more frequent among the !Xun than among the Baka during a period that included the likely !Xun weaning period. Care by young allomaternal caregivers may have played a supportive role during the earlier weaning period associated with sedentarization. DISCUSSION:Human caregiving systems should not be understood as either "mother-centered" or "cooperative". Rather, they should be understood as flexible combinations of interrelated components-including maternal, allomaternal, and peer-based care-shaped by ecological, social, and developmental factors.
OBJECTIVES:The human plantar aponeurosis (PA) is a unique structure that spans the longitudinal arch of the foot, contributing to locomotor efficiency by storing and releasing elastic energy. It is traditionally believed that the PA primarily enhances running economy by reducing muscular effort and metabolic cost. However, the extent to which the PA contributes to walking versus running has not been quantitatively assessed. This study aims to quantitatively compare the mechanical contribution of the PA during walking and running, and to evaluate its relative contribution to whole-body metabolic energy expenditure per unit distance in each gait. MATERIALS AND METHODS:This study investigated the role of the PA in human locomotion by comparing its mechanical contribution during walking and running in 10 healthy adults. Using a detailed foot model and motion capture technology, we quantified PA strain, force, power, and energy release during gait cycles. RESULTS:Peak power and shortening velocity were higher in running, resulting in a significantly larger total energy released by the PA per gait cycle. However, the relative contribution of PA energy to overall metabolic energy expenditure per distance was significantly greater during walking (1.8%) compared to running (1.1%), despite the greater absolute energy output during running. DISCUSSION:These findings challenge the prevailing view that the PA evolved primarily to enhance running efficiency. Instead, the results suggest that the PA plays a relatively larger role in reducing energy consumption during walking, shedding light on the evolutionary adaptation of the human foot for bipedal locomotion.
OBJECTIVES:For anthropologists and forensic scientists, sex estimation using skeletally dimorphic traits is fundamental in biological profile reconstruction. Archaeogenetic research on past populations allows us to identify genetic sex generating opportunities to validate the accuracy of commonly used skeletal traits. We compare genetic sex estimates, derived from aDNA analysis of dental calculus, with macroscopic skeletal observations to ascertain the accuracy of trait-based estimates on British skeletons. MATERIALS AND METHODS:Dental calculus was sampled from 146 individuals from two British sites (Barton-upon-Humber and St James's Gardens [London]), and genetic sex was obtained. A combination of frequently analyzed skull and os coxae traits was assessed to determine overall osteological sex; individual skeletal traits were also evaluated separately. These were then compared to genetic sex. A regression analysis of trait scores was used to identify the best trait combination for sex estimation. RESULTS:We found high agreement between overall osteological sex and genetic sex (97.9%); the os coxa estimate demonstrated almost perfect agreement (97.8%). Skull-based estimates were less accurate (79.0%). Individual Phenice traits demonstrated the greatest accuracy (80.2%-97.5%), whilst multiple skull traits performed poorly (58.9%-68.8%). DISCUSSION:Overall, application of osteological sex estimation techniques to British remains was highly accurate, especially using combined traits of the os coxa. However, we identified multiple skeletal features that are not reliable in isolation, but provide new sectioning points and regression equations to improve skull estimate accuracy. We emphasize the need for further work on factors affecting pelvic morphology, and the benefits of dental calculus as aDNA source.
OBJECTIVES:In human foraging societies, hunting skill is often interpreted as a signal of male quality linked to reproductive success through his ability to provision his family and community. Similarly, in some bird and insect species, males offer mates food to indicate their quality as a provider. Among nonhuman primates, however, the relationship between meat sharing and reproductive success is underexplored, leaving the evolutionary origins of this phenomenon unresolved. MATERIALS AND METHODS:Guinea baboons (Papio papio) are a promising model to investigate whether meat sharing signals male quality, since females choose their mates, have been shown to rely on males to catch and transfer prey, and respond to male foraging skill. We combined records of 109 meat-eating events with 9 years of behavioral data to test whether males who more frequently acquired and transferred meat to females had more females in their social units for longer. RESULTS:Contrary to our predictions, we found no evidence that females preferred males who acquired or transferred meat more frequently, suggesting that meat acquisition is not a signal of male quality in Guinea baboons. DISCUSSION:One explanation may be the relatively low frequency of meat-eating events. Another is that females are less dependent on males for meat than previously reported. Our results revealed that nearly half (41%) of female meat intake originated from sources besides her unit male, including the first documented cases of female prey capture (11% of events) in this species. Thus, females likely apply other, more pertinent criteria in mate choice.
OBJECTIVES:Platycnemia, a mediolateral flattening of the tibial shaft, has been argued to be an adult phenomenon caused by mechanical forces shaping bone. Here we investigate the possibility that this condition develops prior to growth plate closure, at a time when the epiphyseal cartilage is responsive to torsional loading. MATERIALS AND METHODS:We analyze the degree of torsion along the tibial shaft and compare that to the cnemic index (a measure of platycnemia) in two populations: ancient Jomon and modern Japanese. Through linear mixed-effects modeling, we aimed to determine whether platycnemia, as measured by the cnemic index, is correlated with the magnitude of torsion that the tibia undergoes during development, prior to growth plate closure. RESULTS:Our results show that cnemic index significantly decreases as individuals age and the tibia lengthens, resulting in increasing mediolateral flattening and greater instances of platycnemia. However, we found no significant relationship between tibial torsion and the cnemic index. DISCUSSION:Our findings suggest that a broader range of genetic, biomechanical, and environmental properties needs to be considered when hypothesizing how skeletal modeling might be related to the development of platycnemia.
OBJECTIVES:In many rural regions of developing countries, increasing market access is reshaping local food systems. Traditional diets rooted in local agriculture are being replaced by market-driven alternatives. It is suspected that this dietary transition will contribute to rising risks of non-communicable diseases through increased chronic inflammation. This study, conducted in northern Lao People's Democratic Republic, investigated the association between dietary transition and concentrations of C-reactive protein (CRP) as a biomarker of chronic inflammation in three villages with varying levels of market exposure. METHODS:Data were collected from 380 adults in three villages with different degrees of market integration. Questionnaires recorded individual characteristics and weekly intake frequency of 28 food groups. Dried blood spots were analyzed for CRP using enzyme-linked immunosorbent assay. Dietary patterns were identified using principal component analysis, and scores were compared among villages. Associations between dietary patterns and CRP were examined using multivariable logistic regression. To account for seasonality, analyses were conducted within same-season subgroups: rainy (Na Lae, Na Savang) and dry (Na Savang, Nam Nyon). RESULTS:CRP concentrations were higher in villages with a higher degree of market integration. A dietary pattern was identified, characterized by high consumption of foraged wild plants and a low intake of market-related foods. This pattern was negatively associated with elevated CRP in the dry season subsample. CONCLUSIONS:Higher CRP concentrations were found in residents of villages with a higher degree of market integration. This trend may partly be explained by a dietary transition from a foraging-based to a market-dependent diet.
OBJECTIVES:Recent studies of Paranthropus robustus crania identified temporal trends in features associated with increased bite force production, coinciding with environmental shifts toward more arid conditions. To test whether the evolution of postcanine teeth also reflects increasing mechanical demands associated with hard food consumption, we analyzed trends in the architecture of P. robustus postcanine teeth, including crown area, tooth shape, and average (AET) and relative (RET) enamel thickness. MATERIALS AND METHODS:2D mesial sections were created from microCT scans of upper premolars (n = 24), upper molars (n = 14), and lower molars (n = 16) from multiple South African sites. Descriptive statistics, Mann-Whitney U tests, and Jonckheere-Terpstra tests were used to identify significant differences over time, with Holm-Bonferroni corrections applied for multiple comparisons. RESULTS:Significant temporal trends existed in premolar morphology with increased crown area (CA), absolute crown strength (ACS), overall enamel thickness (AET and RET), and increased enamel thickness over the occlusal half of the tooth. Upper molars increased in CA but no other measured variable. Lower molars showed no significant temporal trends in any measured variable. DISCUSSION:These results suggest rapid dental evolution in response to dietary pressures, with varying and independent rates of change between different tooth types. These findings support the hypothesis that selection resulted in shifts to P. robustus dental morphology to increase mechanical resistance, consistent with an expanding dietary niche that incorporated increasingly challenging foods.
Fragmentary preservation represents a fundamental limitation in palaeoanthropological research, particularly for postcranial elements where symmetry cannot be exploited and large portions of bone are frequently missing. Although a wide range of virtual reconstruction methods exist, many rely on strong anatomical priors, localized interpolation, or reference specimens that risk biasing reconstructions toward predefined morphologies. The present study introduces a new approach for estimating the coordinates of missing landmarks, termed the Reverse Engineering (RE) approach. This method establishes mathematical relationships between morphological patterns observed in complete reference specimens and those preserved in reduced portions of each bone, allowing missing regions to be inferred from patterns of covariation rather than local geometric proximity. We demonstrate that the RE approach performs consistently across a range of reconstruction scenarios, including cases where substantial portions of bone are missing, and in empirical applications to Neanderthal femoral and humeral specimens. Importantly, reconstructed specimens retain morphological signal in subsequent morphometric analyses, regardless of the extent of missing data. While limitations remain, as is the case for all reconstruction methods applied to fragmentary fossil material, the RE approach offers a robust and flexible alternative that does not depend on symmetry or a single reference specimen. As such, it represents a valuable addition to the methodological repertoire available to palaeoanthropologists working with incomplete postcranial remains.
OBJECTIVES:Rural populations in northern Laos have experienced dramatic socioeconomic transformation driven by national policies and regional economic integration, substantially influencing their self-sufficient livelihoods. To investigate how these changes have manifested in local subsistence contexts, we compared hair carbon and nitrogen isotope values between two populations representing swidden- and paddy-farming systems, and assessed how isotopic variations reflect the differences in subsistence practices and degrees of livelihood transformation. By analyzing commonly consumed foodstuffs, we provide the first isotopic dataset of foods from northern Laos and baselines for interpreting human tissue isotope values. METHODS:Scalp hair and food samples and sociodemographic data were collected from the study villages. In total, 175 hair and 69 food samples were analyzed. Multiple linear regression analyses were used to examine associations with subsistence/economic and dietary variables. Rice-hair isotopic offsets were calculated to qualitatively assess dietary patterns. RESULTS:Hair δ15N was higher in the paddy-farming village than in the swidden-farming village. In the swidden-farming village, individuals who shifted to paddy cultivation showed higher δ15N and lower δ13C values than those who primarily practiced swidden cultivation. In the paddy-farming village, individuals with greater market involvement exhibited higher hair δ13C values. The rice-hair offsets suggested elevated market food consumption among paddy field cultivators. DISCUSSION:The differences in hair isotope values between (sub)populations can be attributed to isotopic variations in rice, the staple food, and to the differences in market participation. Market integration can lead to an increase in hair δ13C, but the overall isotopic outcome is highly context dependent.
The Osteological Paradox has had an immeasurable impact on bioarchaeology. It has spurred introspection, increased scientific rigor, and encouraged a suite of new and valuable approaches and methods to deal with the challenges it raises. Contrastingly, it has also been perceived as insurmountable, or a problem that simply needs to be acknowledged but not dealt with. In this synthesis, we discuss past and current approaches to the Osteological Paradox, the promise we believe agent-based modeling holds for future research, and broadly contextualize the Paradox within a philosophically optimistic outlook. Our synthesis represents a range of diverse perspectives from bioarchaeology and philosophy, and seeks to identify a path forward. We conclude that the Osteological Paradox represents a springboard more than a hurdle; one that continues to propel the discipline forward and supports the ongoing integration of new technologies to answer questions about past societies.
OBJECTIVES:Cardiovascular disease (CVD) is the leading cause of death for women globally, and menopause is associated with elevated morbidity and mortality. The total impact of menopause on blood pressure remains inconclusive, with evidence largely based on data from industrialized populations. To address this gap, we examined associations between menopause, blood pressure, and hypertension among Tsimane forager-horticulturalists and compared results against a nationally representative US sample to assess population-level differences in blood pressure with menopause. MATERIALS AND METHODS:We analyzed data from female and male Tsimane (nindividuals = 5,570; nobservations = 18,676; ages 15-92) and US National Health and Nutrition Examination Survey participants (NHANES; nindividuals = 6,861; ages 16-80). We applied linear regression models to assess age and population effects on systolic (SBP) and diastolic blood pressure (DBP) with menopause, logistic regression models for hypertension and stage 2 hypertension, and mediation analyses with estradiol. RESULTS:SBP age trajectories were higher (b = 0.002, p < 0.001) and DBP trajectories lower (b = -0.004, p < 0.001) following menopause. Compared to US women, Tsimane women's SBP increased more quickly with age (b = 0.001, p = 0.021), while DBP decreased less dramatically (b = 0.003, p < 0.001). Postmenopause individuals had lower odds of hypertension with age compared to premenopausal women. Estradiol did not mediate blood pressure effects of menopause. DISCUSSION:We found similar associations between menopause and blood pressure in both populations, despite widely differing CVD risk environments. However, Tsimane women showed slightly different pressure changes with age postmenopause. These results indicate blood pressure change postmenopause may be universal, but premenopause CVD risk environments may impact postmenopause CVD risk outcomes.
OBJECTIVES:We have analyzed the elbow ligaments in humans and chimpanzees in order to identify differences that may be related to the use of the upper limbs in these two species. Specifically, we expected to find adaptations to arboreal locomotion and knuckle-walking in chimpanzees and adaptations to non-weight-bearing manual activities in humans. MATERIALS AND METHODS:We dissected seven upper limbs from extant humans and seven from common chimpanzees and performed anatomical and qualitative analyses of the elbow ligaments. Subsequently, we calculated the absolute and relative size of the mass of these ligaments in the two species. RESULTS:The anatomical description of the elbow ligaments was very similar in the two species. The quantitative analysis found a relatively larger anterior fascicle of the ulnar collateral ligament (UCL) in humans and a relatively larger lateral ulnar collateral ligament (LUCL) in chimpanzees. DISCUSSION:The different ways humans and chimpanzees use their upper limbs could explain the quantitative differences we observed in the elbow ligaments. We can thus hypothesize that the more developed anterior fascicle of the UCL in humans may be related to a more pronounced carrying angle in the upper limb and to the valgus forces acting on the elbow during manual tasks. In contrast, the larger LUCL in chimpanzees may help stabilize the elbow during arboreal locomotion and during the support phase of knuckle-walking.
OBJECTIVES:A largely undescribed Late Pleistocene Homo sapiens femur from Wajak, Java, Indonesia (minimum age, 36.5 ka) is reconstructed. In conjunction with data derived from other fossil specimens, we test whether ecogeographic rules relating body size and shape to climate apply to late Middle to Late Pleistocene East Asian Homo. MATERIALS AND METHODS:Preserved portions of the Wajak femur were micro-CT scanned and used to reconstruct the whole bone using a sample of modern human femora as a template. Body mass and stature were reconstructed from femoral head breadth and length. Similar data were derived from eight penecontemporaneous (40-28 ka) and five earlier (ca 260-112 ka) East Asian femora or tibiae, spanning a wide latitudinal range. Anthropometric data from 74 living Old World populations were also included in comparisons. RESULTS:Higher latitude individuals are heavier and relatively wider-bodied than lower latitude individuals in both fossil groups and among modern populations. There is also a temporal decline in body mass and relative body breadth in both latitudinal zones. Stature shows much weaker associations with both climate and time period. The Wajak femur is long (468 mm) and likely male, with an estimated stature of 170.5 cm but a relatively linear body shape, consistent with these patterns. DISCUSSION:Ecogeographic rules that relate surface area/body mass to temperature appear to apply to East Asian late Middle to Late Pleistocene Homo as well as modern humans. The temporal decline in body mass and breadth may be due to technological changes during the Late Pleistocene.
