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This study proposes a new way to use metatarsals to identify locomotor behavior of fossil hominins. Metatarsal head articular dimensions and diaphyseal strength in a sample of chimpanzees, gorillas, orangutans, and humans (n = 76) are used to explore the relationships of these parameters with different locomotor modes. Results show that ratios between metatarsal head articular proportions and diaphyseal strength of the hallucal and fifth metatarsal discriminate among extant great apes and humans based on their different locomotor modes. In particular, the hallucal and fifth metatarsal characteristics of humans are functionally related to the different ranges of motion and load patterns during stance phase in the forefoot of humans in bipedal locomotion. This method may be applicable to isolated fossil hominin metatarsals to provide new information relevant to debates regarding the evolution of human bipedal locomotion. The second to fourth metatarsals are not useful in distinguishing among hominoids. Further studies should concentrate on measuring other important qualitative and quantitative differences in the shape of the metatarsal head of hominoids that are not reflected in simple geometric reconstructions of the articulation, and gathering more forefoot kinematic data on great apes to better understand differences in range of motion and loading patterns of the metatarsals. Am J Phys Anthropol 143:198-207, 2010. [c] 2010 Wiley-Liss, Inc. KEY WORDS forefoot; metatarsophalangeal joint; australopithecine locomotion; cross-sectional geometry; metatarsus DOI 10.1002/ajpa.21306

Life-history inference is an important aim of paleoprimatology, but life histories cannot be discerned directly from the fossil record. Among extant primates, the timing of many life-history attributes is correlated with the age at emergence of the first permanent molar (M1), which can therefore serve as a means to directly compare the life histories of fossil and extant species. To date, M1 emergence ages exist for only a small fraction of extant primate species and consist primarily of data from captive individuals, which may show accelerated dental eruption compared with free-living individuals. Data on M1 emergence ages in wild great apes exist for only a single chimpanzee individual, with data for gorillas and orangutans being anecdotal. This paucity of information limits our ability to make life-history inferences using the M1 emergence ages of extinct ape and hominin species. Here we report reliable ages at M1 emergence for the orangutan, Pongo pygmaeus (4.6 y), and the gorilla, Gorilla gorilla (3.8 y), obtained from the dental histology of wild-shot individuals in museum collections. These ages and the one reported age at M1 emergence in a free-living chimpanzee of approximately 4.0 y are highly concordant with the comparative life histories of these great apes. They are also consistent with the average age at M1 emergence in relation to the timing of life-history events in modern humans, thus confirming the utility of M1 emergence ages for life-history inference and providing a basis for making reliable life-history inferences for extinct apes and hominins. dental histology | great apes | tooth eruption | tooth growth doi/10.1073/pnas.0906206107

Previous studies have referred to the degree of dorsal canting of the base of the proximal phalanx as an indicator of human-like metatarsophalangeal joint function and thus a diagnostic trait of habitual bipedality in the fossil record. Here, we used a simple method to investigate differences in forefoot function on a finer scale. Building on Duncan et al.'s (Am J Phys Anthropol 93 [1994] 67-81) research, we tested whether dorsal canting reflects differences between sexes in locomotor behavior, whether habitual shoe wear influences dorsal canting in humans, and whether proximal joint morphology differs between rays in Pan and humans. Our results corroborate previous research in showing that humans have proximal phalanges with joint orientations that are significantly more dorsal than, but overlap with, those of great apes. We also found that male gorillas have significantly more dorsally canted second proximal phalanges than their female counterparts, while the opposite pattern between the sexes was found in Pan troglodytes. Inter-ray comparisons indicate that Pan have more dorsally canted first proximal phalanges than second proximal phalanges, while the opposite pattern was found in humans. Minimally shod humans have slightly but significantly more dorsally canted second proximal phalanges than those of habitually shod humans, indicating that phalanges of unshod humans provide the most appropriate comparative samples for analyses of early hominins. Overall, our analysis suggests that though the measurement of dorsal canting is limited in its sensitivity to certain intraspecific differences in function, phalangeal joint orientation reflects interspecific differences in joint function, with the caveat that different patterns of forefoot function during gait can involve similar articular sets of metatarsophalangeal joints. Am J Phys Anthropol 141:116-123, 2010. [c] 2009 Wiley-Liss, Inc. KEY WORDS Australopithecus afarensis; dorsal canting; hallux; metatarsophalangeal joint DOI 10.1002/ajpa.21121

Lucas and colleagues recently proposed a model based on fracture and deformation concepts to describe how mammalian tooth enamel may be adapted to the mechanical demands of diet (Lucas et al.: Bioessays 30[2008] 374-385). Here we review the applicability of that model by examining existing data on the food mechanical properties and enamel morphology of great apes (Pan, Pongo, and Gorilla). Particular attention is paid to whether the consumption of fallback foods is likely to play a key role in influencing great ape enamel morphology. Our results suggest that this is indeed the case. We also consider the implications of this conclusion on the evolution of the dentition of extinct hominins. Am J Phys Anthropol 140:653-660, 2009. KEY WORDS fracture mechanics; diet; evolution DOI 10.1002/ajpa.21096

Despite decades of debate, it remains unclear whether human bipedalism evolved from a terrestrial knuckle-walking ancestor or from a more generalized, arboreal ape ancestor. Proponents of the knuckle-walking hypothesis focused on the wrist and hand to find morphological evidence of this behavior in the human fossil record. These studies, however, have not examined variation or development of purported knuckle-walking features in apes or other primates, data that are critical to resolution of this long-standing debate. Here we present novel data on the frequency and development of putative knuckle-walking features of the wrist in apes and monkeys. We use these data to test the hypothesis that all knuckle-walking apes share similar anatomical features and that these features can be used to reliably infer locomotor behavior in our extinct ancestors. Contrary to previous expectations, features long-assumed to indicate knuckle-walking behavior are not found in all African apes, show different developmental patterns across species, and are found in nonknuckle-walking primates as well. However, variation among African ape wrist morphology can be clearly explained if we accept the likely independent evolution of 2 fundamentally different biomechanical modes of knuckle-walking: an extended wrist posture in an arboreal environment (Pan) versus a neutral, columnar hand posture in a terrestrial environment (Gorilla). The presence of purported knuckle-walking features in the hominin wrist can thus be viewed as evidence of arboreality, not terrestriality, and provide evidence that human bipedalism evolved from a more arboreal ancestor occupying the ecological niche common to all living apes. bipedalism | development | hominoid | homoplasy | wrist

This study provides a survey of mandibular shape in a sample of extant hominoids (Pan, Gorilla, Pongo, and Hylobates), as well as extinct Asian and Eurasian taxa (Ouranopithecus, Sivapithecus, and Gigantopithecus) in order to compare overall shape similarity. Results presented call into question differences in mandible shape recently used to distinguish Gigantopithecus giganteus from Gigantopithecus blacki and to justify resurrecting a different generic designation, 'Indopithecus,' for the former. It is concluded that while the two large-bodied Asian taxa may have been adapted to slightly different dietary niches with different geographic and temporal ranges, the unique mandibular/ dental characters that the two taxa share should not be viewed as independent evolutionary developments. KEY WORDS relative warps analysis; allometry; diet; cluster analysis; G. blacki; G. giganteus

In the recent description of the hominin postcranial material from Dmanisi, Georgia, Lordkipanidze and colleagues (Lordkipanidze et al. [2007] Nature 449: 305-310) claim that the Dmanisi hominins walked with more medially oriented feet than do modern humans. They draw this functional inference from two postcranial features: a wide talar neck angle and a slight medial torsion of the tibia. However, we believe that the data provided by the authors fail to support their conclusions. Talar neck angle and tibial torsion values from the Dmanisi specimens fall comfortably within the range of modern human variation. We further submit that foot orientation cannot be reliably deduced from the tibia and talus alone. KEY WORDS talar neck angle; tibial torsion; in-toeing

This article examines the curvature of the manual proximal and middle phalanges of species belonging to Pan, Gorilla, Ateles, Macaca, Pongo, Hylobates, and Cebus to determine whether middle phalangeal curvature, when considered in conjunction with proximal phalangeal curvature, yields a locomotor signal. Prior studies have demonstrated the discriminatory power of proximal phalanges for separating suspensory species (including knuckle walkers) from pronograde quadrupedal species, but less emphasis has been placed on the distinguishing phalangeal characteristics of taxa within the suspensory category. This study demonstrates, first, that middle phalanges discriminate suspensory from nonsuspensory species, although not as cleanly as proximal phalanges. Finer discrimination of locomotor signals, including subtle differences among animals employing different modes of suspension, is possible through a comparison of the curvatures of the proximal phalanges and corresponding middle phalanges. Their relative curvature differs in quadrupeds, brachiators, and knuckle walkers. Knuckle walkers (Pan and Gorilla) have relatively little curvature of the middle phalanges coupled with marked curvature of the proximal phalanges, whereas brachiators (Ateles and Hylobates) display marked curvature of both proximal and middle phalanges, and pronograde quadrupeds (Cebus and Macaca) have relatively straight proximal and moderately curved middle phalanges. Quadrumanous climbers (Pongo) have a unique combination of traits, whereby curvature is high in both proximal and middle phalanges, but less so in the latter than the former. These differences, predictable on the basis of the biomechanical forces to which digits are subjected, may open a new venue for future research on the locomotor repertoire of prebipedal ancestors of hominins. 2008. KEY WORDS phalangeal curvature; locomotion; African apes; Pongo; Macaca; Cebus; Ateles

Great apes are the closest living relatives of humans. Physiological similarities between great apes and humans provide clues to identify which biological features in humans are primitive or derived from great apes. Vitamin A (VA) and carotenoid metabolism have been only partially studied in great apes, and comparisons between great apes and humans are not available. We aimed to investigate VA and carotenoid intake and plasma concentrations in great apes living in captivity, and to compare them to healthy humans. Dietary intakes of humans (n = 20) and, among the great apes, chimpanzees (n = 15) and orangutans (n = 5) were calculated. Plasma retinol (ROH), retinol-binding protein (RBP), retinyl esters, and major carotenoids were analyzed. The great ape diet was higher in VA than in humans, due to high intake of provitamin A carotenoids. Plasma ROH concentrations in great apes were similar to those in humans, but retinyl esters were higher in great apes than in humans. Differences in plasma carotenoid concentrations were observed between great apes and humans. Lutein was the main carotenoid in great apes, while [beta]-carotene was the main carotenoid for humans. RBP concentrations did not differ between great apes and humans. The molar ratio of ROH to RBP was close to 1.0 in both great apes and humans. In conclusion, great apes show homeostatic ROH regulation, with high but physiological retinyl esters circulating in plasma. Furthermore, great apes show great selectivity in their plasmatic carotenoid concentration, which is not explained by dietary intake. KEY WORDS vitamin A; diet; retinol-binding protein; chimpanzee; orangutan

We present the microbiological and molecular characterization of bacteria isolated from four chimpanzees and one gorilla thought to have died of an anthrax-like disease in Cote d'Ivoire and Cameroon. These isolates differed significantly from classic Bacillus anthracis by the following criteria: motility, resistance to the gamma phage, and, for isolates from Cameroon, resistance to penicillin G. A capsule was expressed not only after induction by C[O.sub.2] and bicarbonate but also under normal growth conditions. Subcultivation resulted in beta-hemolytic activity and gamma phage susceptibility in some subchmes, suggesting differences in gene regulation compared to classic B. anthracis. The isolates from Cote d'Ivoire and Cameroon showed slight differences in their biochemical characteristics and MICs of different antibiotics but were identical in all molecular features and sequences analyzed. PCR and Southern blot analyses confirmed the presence of both the toxin and the capsule plasmid, with sizes corresponding to the B. anthraeis virulence plasmids pXO1 and pXO2. Protective antigen was expressed and secreted into the culture supernatant. The isolates possessed variants of the Ba813 marker and the SG-749 fragment differing from that of classic B. anthraeis strains. Multilocus sequence typing revealed a close relationship of our atypical isolates with both classic B. anthracis strains and two uncommonly virulent Bacillus cereus and Bacillus thuringiensis isolates. We propose that the newly discovered atypical B. anthraeis strains share a common ancestor with classic B. anthracis or that they emerged recently by transfer of the B. anthracis plasmids to a strain of the B. cereus group.

Investigations of cross-sectional geometry in nonhuman primate limb bones typically attribute shape ratios to qualitative behavioral characterizations, e.g., leaper, slow climber, brachiator, or terrestrial vs. arboreal quadruped. Quantitative positional behavioral data, however, have yet to be used in a rigorous evaluation of such shape-behavior connections. African apes represent an ideal population for such an investigation because their relatedness minimizes phylogenetic inertia, they exhibit diverse behavioral repertoires, and their locomotor behaviors are known from multiple studies. Cross-sectional data from femoral and humeral diaphyses were collected for 222 wild-shot specimens, encompassing Pan paniscus and all commonly recognized African ape subspecies. Digital representations of diaphyseal cross sections were acquired via computed tomography at three locations per diaphysis. Locomotor behaviors were pooled broadly into arboreal and terrestrial categories, then partitioned into quadrupedal walking, quadrumanous climbing, scrambling, and suspensory categories. Sex-specific taxonomic differences in ratios of principal moments of area (PMA) were statistically significant more often in the femoral diaphysis than the humeral diaphysis. While it appears difficult to relate a measure of shape (e.g., PMA ratiot to individual locomotor modes, general locomotor differences (e.g., percentage arboreal vs. terrestrial locomotion) are discerned more easily. As percentage of arboreal locomotion for a group increases, average cross sections appear more circular. Associations between PMA ratio and specific locomotor behaviors are less straightforward. Individual behaviors that integrate eccentric limb positions (e.g., arboreal scrambling) may not engender more circular cross sections than behaviors that incorporate repetitive sagittal movements (e.g., quadrupedal walking) in a straightforward manner. KEY WORDS cross-sectional geometry; principal moment of area; locomoter behavior; Pan; Gorilla

Body mass estimation equations are generated from long bone cross-sectional diaphyseal and articular surface dimensions in 176 individuals and 12 species of hominoids and cercopithecoids. A series of comparisons is carried out to determine the best body mass predictors for each of several taxonomic/locomotor groupings. Articular breadths are better predictors than articular surface areas, while cross-sectional shaft strengths are better predictors than shaft external breadths. Percent standard errors of estimate (%SEEs) and percent prediction errors for most of the better predictors range between 10-20%. Confidence intervals of equations using sex/species means are fairly representative of those calculated using individual data, except for sex/species means equations with very low %SEEs (under about 10%), where confidence intervals (CIs) based on individuals are likely to be larger. Given individual variability, or biological 'error,' this may represent a lower limit of precision in estimating individual body masses. In general, it is much more preferable to determine at least broad locomotor affinities, and thus appropriate modern reference groups, before applying body mass estimation equations. However, some structural dimensions are less sensitive to locomotor distinctions than others; for example, proximal tibial articular M-L breadth is apparently 'locomotor blind' regarding body mass estimation within the present study sample. In other cases where locomotor affiliation is uncertain, mean estimates from different reference groups can be used, while for some dimensions no estimation should be attempted. The techniques are illustrated by estimating the body masses of four fossil anthropoid specimens of Proconsul nyanzae, Proconsul heseloni, Morotopithecus bishopi, and Theropithecus oswaldi. Am J Phys Anthropol 120:16-37, 2003. KEY WORDS skeleton; postcranial; hominoid; cercopithecoid; body weight

The authors examine how sexual selection affects evolution relative to seminal vesicle function, testes size, sperm and penile morphology, copulatory behavior and cryptic female choice in various primates. Species studied include various apes, monkeys, and human beings.

One of the few uncontested viewpoints in studies of enamel thickness is that the molars of the African apes, Pan and Gorilla, possess 'thin' enamel, while Pongo and modern humans possess varying degrees of 'thick' enamel, even when interspecific differences in overall body or tooth size are taken into account. Such studies focus primarily on estimates of the total volume of enamel relative to tooth size (i.e., 'relative' enamel thickness), as this is thought to bear directly on questions concerning dietary proclivities and phylogenetic relationships. Only recently have studies shifted focus to examining differences in the distribution of enamel across the tooth crown, i.e., the patterning of enamel thickness, as this may contribute to more refined models of tooth function and dietary adaptations in extant hominoids. Additionally, this feature has been suggested to be a reliable indicator of taxonomic affinity in early hominins, though no study has specifically addressed whether species-specifc patterns exist among known phena. The aims of this paper were to test more explicitly whether enamel thickness patterning provides valuable taxonomic, functional, and/or phylogenetic information for maxillary molars of large-bodied extant hominoids. A series of seven linear enamel thickness measurements was recorded in the plane of the mesial cusps in cross sections of a total of 62 maxillary molars of P. troglodytes, G. gorilla, P. pygmaeus, and H. sapiens to estimate the patterning of enamel thickness distribution. Results from a discriminant function analysis reveal that, overall, this trait reclassifies extant hominoid maxillary molars with 90% accuracy: 100% of extant Homo, 75.0% of Pongo, 83.3% of Pan, and 66.7% of Gorilla are reclassified correctly, indicating that this feature possesses a strong taxonomic signal. Furthermore, differences in the structure of the enamel cap are evident among hominoids: modern humans differ from Pongo in possessing proportionally thicker enamel in areas of the crown associated with shearing activity; Pan molars are better designed than those of Gorilla for generating a greater component of crushing/grinding loads. Thus, African ape molars are structurally dissimilar, even though they are both considered to belong to a morphologically homogeneous 'thin-enameled' group. Simple developmental mechanisms can be invoked to explain the sometimes subtle differences in the achievement of adult morphology. For instance, human and orangutan molar cusps possess a similar degree of enamel thickness, but the possibility exists that despite similarities in morphology, each species follows a different sequence of secretory activity of enamel to achieve the final, albeit similar, degree of enamel thickness. Such a finding would suggest that the shared possession of'thick' or 'thin' enamel among species may be phylogenetically uninformative, as it would not represent a developmental synapomorphy. Keywords: enamel thickness; maxillary molars; modern humans; great apes; mastication; tooth function; diet; enamel development

This paper presents new data on enamel hypoplasia in the deciduous canine teeth of great apes. The enamel defect under consideration is known as localized hypoplasia of primary canines (LHPC), and is characterized by an area of thin or missing enamel on the labial surface of deciduous canine teeth (Skinner [1986a] Am. J. Phys. Anthropol. 69:59-69). Goals of this study are: 1) to determine if significant differences in the frequency of LHPC occur among three genera of great apes, and 2) to evaluate variation in LHPC prevalence among great apes as evidence of differential physiological stress. Infant and juvenile apes with deciduous teeth were examined at the Cleveland Museum of Natural History (n = 100) and at the Smithsonian Institution, National Museum of Natural History (n= 36). Deciduous teeth were observed under oblique incandescent light, with the naked eye and with a 10x hand lens. Enamel hypoplasia was scored using Federation Dentaire International (FDI)-Defects of Dental Enamel (DDE) standards. Hypoplasias were recorded by drawing defect location and size on a dental chart, and by measuring defect size and location with Helios needlepoint dial calipers. The prevalence of LHPC is reported by genus and sex, using two approaches: 1) the frequency of affected individuals - those having one or more deciduous canine teeth scored positive for LHPC; and 2) the number of canine teeth scored positive for LHPC as a percentage of all canine teeth observed. Variation in defect size and location will be described elsewhere. Localized hypoplasia of primary canine teeth was found in 62.5% of 128 individual apes, and in 45.5% of 398 great ape deciduous canines. As in humans, LHPC is the most common form of enamel hypoplasia in deciduous teeth of great apes, while LEH is rare or absent. The distribution and pattern of expression of LHPC in great apes is similar to that described in humans: side differences are not significant, but mandibular canines exhibit the defect two to five times more often than maxillary canine teeth. Differences in LHPC prevalence by sex are small and not significant. Intergeneric differences are large and non-random: chimpanzees (Pan) exhibit a significantly lower frequency of LHPC (22%, n = 50) by individual count, than either the orangutan (Pongo, 88.0%, n=25) or the gorilla (Gorilla, 88.7%, n = 53). Tooth count prevalences exhibit a similar pattern of variation and are also statistically significant. These finding suggest that large bodied great apes (gorilla and orangutan) may be under greater physiological stress during perinatal and early postnatal development than the chimpanzee. The size, position, and timing of LHPC lesions are currently under analysis and may yield more insight into the etiological origin of this enamel defect. Key Words: enamel hypoplasia; enamel defect; localized hypoplasia; deciduous teeth; hominoids; great apes

We report the existence and distribution of an unusual type of projection neuron, a large, spindle-shaped cell, in layer Vb of the anterior cingulate cortex of pongids and hominids. These spindle cells were not observed in any other primate species or any other mammalian taxa, and their volume was correlated with brain volume residuals, a measure of encephalization in higher primates. These observations are of particular interest when considering primate neocortical evolution, as they reveal possible adaptive changes and functional modifications over the last 15-20 million years in the anterior cingulate cortex, a region that plays a major role in the regulation of many aspects of autonomic function and of certain cognitive processes. That in humans these unique neurons have been shown previously to be severely affected in the degenerative process of Alzheimer's disease suggests that some of the differential neuronal susceptibility that occurs in the human brain in the course of age-related dementing illnesses may have appeared only recently during primate evolution.

Functional and allometric analyses of the hand of the late Miocene ape Oreopithecus bambolii (Tuscany, Italy) reveal a series of features that reflect an improved grasping capability including firm pad-to-pad precision gripping that apes are unable to perform. Related features such as hand length, relative thumb length, a deep and large insertion area for the tendon of the long thumb flexor, and the form of the metacarpal 2/capitate articulation are not present in extant or fossil apes. In these features, the Oreopithecus hand closely matches the pattern of early hominids, presumably as a response to similar functional demands.

The limbic frontal cortex forms part of the neural substrate responsible for emotional reactions to social stimuli. Area 13 is one of the cortical areas long known to be part of the posterior orbitofrontal cortex in several monkey species, such as the macaque. Its presence nevertheless in the human brain has been unclear, and the cortex of the frontal lobe of the great and lesser apes remains largely unknown. In this study area 13 was identified in human, chimpanzee, bonobo, gorilla, orangutan, and gibbon brains, and cortical maps were generated on the basis of its cytoarchitecture. Imaging techniques were used to characterize and quantify the microstructural organization of the area, and stereological tools were applied for estimates of the volume of area 13 in all species. Area 13 is conservative in its structure, and features such as size of cortical layers, density of neurons, and space available for connections are similar across hominoids with only subtle differences present. In contrast to the homogeneity found in its organization, variation is present in the relative size of this cortical area (as a percentage of total brain volume). The human and the bonobo include a complex orbitofrontal cortex and a relatively smaller area 13. On the contrary the orangutan stands out by having a shorter orbitofrontal region and a more expanded area 13. Differences in the organization and size of individual cortical areas involved in emotional reactions and social behavior can be related to behavioral specializations of each hominoid and to the evolution of emotions in hominids. KEY WORDS orbitofrontal; neuroanatomy; brain; cytoarchitecture; stereology; apes; humans; evolution

Hand use in gestural communication was examined in 115 captive chimpanzees (Pan troglodytes). Hand use was measured in subjects while they gestured to food placed out of their reach. The distribution of hand use was examined in relation to sex, age, rearing history, gesture type, and whether the subjects vocalized while gesturing. Overall, significantly more chimpanzees, especially females and adults, gestured with their right than with their left hand. Foods begs were more lateralized to the right hand than pointing, and a greater prevalence of right-hand gesturing was found in subjects who simultaneously vocalized than those who did not. Taken together, these data suggest that referential, intentional communicative behaviors, in the form of gestures, are lateralized to the left hemisphere in chimpanzees.

Oliver is an African ape whose species identity has been debated in the popular media and by various scientists since the early 1970s. Although decisive morphological data has never been adduced on Oliver, many reports indicated that Oliver was morphologically unusual for a chimpanzee, particularly in his habitual bipedal posture. In addition, his diploid chromosome number was reported to be inconsistent with either human or chimpanzee, but instead intermediate between those species. We performed standard chromosomal studies which demonstrated that Oliver had the diploid number expected for a chimpanzee (2N = 48) and that the banding patterns of his chromosomes were typical for a chimpanzee and different from both humans and bonobos. We also sequenced a 312 bp region of his mitochondrial DNA D-loop region. Results indicated a high sequence homology to the Central African variety of chimpanzee, Pan troglodytes troglodytes. The highest percent homology was observed with a previously characterized specimen from Gabon, strongly suggesting that Oliver originated from this region. KEY WORDS C-banding; chimpanzees; G-banding; karyotypes; phylogeography

Skull similarities are often used to determine ancestor-descendant links between fossil and living ape genera, particularly between late Miocene apes and and the living Sumatran orang-utan. However well preserved fossil crania of the Old World monkeys, is rare. A complete skull of Victoriapithecus at middle Miocene deposits in Kenya has been discovered, representing a branch of Old World monkey intermediate between extant cercopithecids and common ape ancestors.

The present analysis evaluated extant hominoid subnasal morphological variation from an ontogenetic perspective, documenting both qualitative and allometric details of subnasal maturation in Hylobates, great apes and modern humans. With respect to intraspecific variation, results of log-linear modeling procedures indicate that qualitative features of the subnasal region shown previously to discriminate extant taxa (Ward and Kimbel, 1983; McCollum et al., 1993) do not vary appreciably with either age or sex. In terms of quantitative variation, aside from observed changes in the position of the anterior attachment of the nasal septal cartilage relative to the lateral margins of the nasal cavity, the morphology of the subnasal region does not vary appreciably with age. Furthermore, it was found that sexual dimorphism in subnasal form is present only in Pongo and Gorilla and is the result of sexual bimaturism rather than sexual variation in canine size. In considering interspecific variation in subnasal form, there is a propensity among hominoid taxa for the nasal cavity floor to be free of substantial topographic relief. The smoothly continuous nasal floor topography identified in the majority of hominoid taxa appears to be produced by extensive resorption of the anterior nasal cavity floor that accompanies an upward rotation of the anterior maxilla during craniofacial ontogeny. Comparisons of ontogenetic allometric trajectories indicate that relatively little of the variation in hominoid subnasal form can easily be attributed to variation in body/cranial size. Instead, variation in craniofacial orientation, vascular anatomy and incisor size and inclination were identified as potential mediators of hominoid subnasoalveolar anatomy. Although results of this analysis confirm that many details of the orangutan subnasal morphology are derived for this taxon, there is little conclusive evidence to support recent reports that the morphology displayed by Gorilla is primitive for great apes (Begun, 1992, 1994). KEY WORDS hylobatids; great apes; Homo; subnasal development; ontogenetic allometry; facial kyphosis; character phylogeny

A comparative study of carpal joint structure and function in six Malagasy lemuriforms was undertaken to test predicted morphoclines in carpal joint morphology between pronograde and orthograde arboreal primates. Patterns of movement at the wrist during locomotion were observed and described for the lemuriform species Lemur fulvus and Propithecus verreauxi. Lemur fulvus, which assumes a pronograde posture during locomotion, extends and pronates the wrist during the support phase of quadrupedal walking and running stride cycles. Furthermore, the forearm of this species exhibits some transverse movement across the proximal wrist joint during the support phase. In contrast, the indriid Propithecus maintains the hand and wrist in a flexed and partially supinated position during vertical clinging and suspensory postures. Habitual quadrupedal and vertical postures in Malagasy primates are in turn related to very different patterns of carpal joint morphology and articular mechanics. Those lemurs which are predominantly pronograde share a series of structural features related to stabilizing the antebrachiocarpal joint during extension and mediolateral deviation and the midcarpal joint during pronation: an intraarticular labrum is present on the inner portion of the radiocarpal ligament, the radiocarpal articular surface is quite flat dorsoventrally, the capitate-trapezoid embrasure is expanded dorsally, and development of the radial and ulnar styloids is more pronounced. The wrists of Propithecus, Avahi, and Lepilemur (vertical clingers) differ from those of quadrupedal lemuriforms in possessing a suite of morphological features related to stabilizing the wrist during antebrachiocarpal flexion and midcarpal supination: the radiocarpal articular surface is deeply curved and tilted anteriorly, the dorsal radiocarpal ligament is very broad, thick, and fibrous, the hamate's triquetral facet is directed proximodistally, and the capitate-trapezoid embrasure is dorsally constricted and expanded palmarly. These observed contrasts in carpal form and function are used to define further the morphological features related to orthograde posture in several lineages of arboreal primates. KEY WORDS Carpal joints, Quadrupedalism, Vertical clinging, Orthograde posture

The sciatic notch has been widely used as a sexing criterion in modern humans. In order to better understand the sex differences of this feature in modern humans and great apes, four measurements of the sciatic notch were taken on samples of modern humans and great apes of known sex. Univariate (ANOVA) analysis and discriminant function analysis were performed on the extant taxa to determine: (1) the discriminating power of each variable in these samples of known group membership; and (2) which of these extant taxa shows the best discrimination between the sexes for the sciatic notch. Of the four extant taxa, the sciatic notch of Homo sapiens is the most sexually dimorphic, followed by Gorilla gorilla, and more weakly by Pongo pygmaeus, while Pan troglodytes is the least dimorphic of these taxa. Since the presence of a well defined sciatic notch is a hominid trait resulting from the dorsal extension of the posterior ilium, the close approximation of the sacrum to the acetabulum, the shortened ischium, and the accentuation of the ischial spine as part of the bipedal adaptation, it seems likely that the configuration of the sciatic notch in hominids was initially related to bipedalism, not reproduction. The development of sex differences in the sciatic notch of modern humans is more likely to have occurred after the transition to bipedality. KEY WORDS Pelvic dimorphisms, Great apes, Modern humans, Discriminant function analysis

There have been numerous attempts to sex fossil specimens using the canine dentition. Whether focused on canine size or canine shape, most of these efforts share two deficiencies: lack of quantification of male-female differences in the adopted criteria and a failure to adequately explore among extant species the discriminatory power of these criteria. Here, canine shape indices relating to relative canine height, upper canine root/crown proportionality, and relative length of the lower canine mesial ridge were calculated for males and females of all species and subspecies of extant great apes and two species of gibbons. The accuracy of these indices for identifying the sex of the extant ape specimens was investigated through discriminant analysis and the use of bivariate plots of the two upper and two lower canine indices. The indices were found to be highly accurate in identifying the sex of great ape individuals, not only in single-species and subspecies samples but in mixed-species samples as well; assignment error rates were mostly between 0 and 4%. Accuracy was lowest in Pan (error rates as high as 15%) and highest in Pongo (one error). In most cases, error rates were lower in the upper canines. The effectiveness of these shape indices for sexing might be related to the degree of absolute canine size dimorphism; the indices did not effectively segregate males and females among minimally canine-dimorphic gibbons. The mixed-species results reveal that same-sex index values are remarkably concordant across great ape species, as are the patterns of spatial segregation of males and females in the bivariate plots. Results suggest that, while the indices can be used with some confidence to sex individual fossil specimens, their greatest utility will be for identifying the sex of groups of canines united by size and morphology. KEY WORDS Pan, Gorilla, Pongo, Hylobates, Apes, Canine teeth, Sexing, Sexual dimorphism

Arterial meningeal patterns were observed for 100 hemispheres from great ape endocasts (Pan paniscus, Pan troglodytes, Gorilla gorilla, and Pongo pygmaeus). Eight patterns emerged based on the relative contributions to the walls and dura mater of the middle part of the braincase of meningeal arteries that stem from two sources. These arteries enter the braincase through either the orbit (delivering blood from the internal carotid artery) or through the base of the middle cranial fossa (via the middle meningeal artery whose blood comes from the external carotid artery). The three genera of apes manifest different frequencies of the eight patterns, with orangutans highly dependent on orbital meningeal arteries at one extreme, and chimpanzees showing the greatest reliance on the middle meningeal artery at the other. As was the case in an earlier study of rhesus monkeys, there is a trend across the two genera of African apes for increased mean cranial capacity to be associated with increased reliance on the internal carotid artery for supplying the middle portion of the braincase. However, unlike the case for macaques, this trend does not reach statistical significance in African apes. Because it is rare for humans to manifest significant arterial contributions from the orbit to the middle cranial fossa, the comparative data on monkeys, apes, and humans suggest that, during the course of vascular evolution in Homo, the middle meningeal artery eventually took over supply of the entire middle cranial fossa. This hypothesis should be tested in the hominid fossil record. Earlier work on meningeal arterial patterns in apes has traditionally relied on Adachi's system that was determined from humans and focuses on the origin of the middle branch of the middle meningeal artery. As a result, the extensive orbital contributions to the middle portion of the braincase that characterize apes were not recognized and the eight patterns described in this paper were often erroneously assigned to the three patterns that adequately describe only humans. Adachi's system should therefore be abandoned for nonhuman primates and early hominids. A correct understanding of meningeal arterial evolution cannot be achieved until the orbital contributions to the meningeal arteries are recognized and incorporated into an evolutionary study that spans from apes to fossil hominids to living people.

We obtained electromyographic recordings from the supinator, biceps brachii, pronator quadratus, and pronator teres muscles of a chimpanzee and a gorilla and from the supinator, pronator quadratus, and biceps brachii muscles of an orangutan as they stood and walked quadrupedally on horizontal and inclined surfaces, engaged in suspensory behavior, reached overhead, and manipulated a variety of foods and artifacts. In Pan troglodytes and Pan gorilla, as in Homo sapiens, the supinator muscle is the prime supinator, with the bicpes brachii muscle serving to augment speed or force of supination. Primacy of the pronator quadratus muscle over the pronator teres muscle during pronation is less clear in the African apes than in humans. Possibly, pongid radial curvature of forelimb elongation or both factors are related to the somewhat different patterns of activity that we observed in the pronator muscles of Pan versus those reported for Homo sapiens. In Pongo pygmaeus, as in P. troglodytes and P. gorilla, the pronator quadratus muscle acts as a pronator and the supinator muscle acts to supinate the hand at the radioulnar joints. The biceps brachii muscle is active at low levels as the orangutan supinates its hand with the elbow flexed.

The single previous study on tooth development in great apes (Dean and Wood: Folia Primatol. (Basel) 36:111-127, 1981) is of limited value because it is based on cross-sectional radiographic data. This study considers problems in defining stages of tooth development in radiographs of developing ape dentitions and provides data on tooth chronology in Pongo pygmaeus and Gorilla gorilla by using histological methods of analysis. Crown formation times were estimated in individual teeth, and an overall chronology of dental development was found by registering teeth forming at the same time by using incremental growth lines. The earlier radiographic study correctly identified the molar and second premolar chronology and sequence in great apes, but significantly underestimated crown formation times in incisors, first premolars, and canine teeth in particular. Ape anterior tooth crowns take longer to form than the equivalent human teeth, but the overall dental developmental period in great apes is substantially shorter than in humans. Gorilla root extension rates appear to be fast, up to approximately 13 [mu]m/day. This rapid root growth, associated with early tooth eruption, appears to be the developmental basis for the observed differences in timing between developing dentitions in great apes and humans.

The comparison of the brain structure of mountain gorillas (Gorilla beringei beringei) with other great apes is presented. 3 mountain gorilla brains were obtained with a 3T scanner and the volume of neuroanatomical structures were measured and it was found that the brain structure of great apes differ mostly in the sizes of the striatum, cerebellum, and hippocampus.

How do arm-swinging apes locomote effectively over a variety of speeds? One way to reduce the metabolic energy cost of locomotion is to transfer energy between reversible mechanical modes. In terrestrial animals, at least two transfer mechanisms have been identified: 1) a pendulum-like mechanism for walking, with exchange between gravitational potential energy and translational kinetic energy, and 2) a spring-like mechanism for running, where the elastic strain energy of stretched muscle and tendon is largely returned to reaccelerate the animal. At slower speeds, a brachiator will always have at least one limb in contact with the support, similar to the overlap of foot contact in bipedal walking. At faster speeds, brachiators exhibit an aerial phase, similar to that seen in bipedal running. Are there two distinct brachiation gaits even though the animal appears to simply swing beneath its overhead support? If so, are different exchange mechanisms employed? Our kinetic analysis of brachiation in a white-handed gibbon (Hylobates lar) indicates that brachiation is indeed comprised of two mechanically distinct gaits. At slower speeds in 'continuous contact' brachiation, the gibbon utilizes a simple pendulum-like transfer of mechanical energy within each stride. At faster speeds in 'ricochetal' brachiation, translational and rotational kinetic energy are exchanged in a novel 'whip-like' transfer. We propose that brachiators utilize the transfer between translational and rotational kinetic energy to control the dynamics of their swing. This maneuver may allow muscle action at the shoulder to control the transfer and adjust the ballistic portion of the step to meet the requirements for the next hand contact. Am J Phys Anthropol 115:319-326, 2001. KEY WORDS locomotion; gibbon; energy

Area 10 is one of the cortical areas of the frontal lobe involved in higher cognitive functions such as the undertaking of initiatives and the planning of future actions. It is known to form the frontal pole of the macaque and human brain, but its presence and organization in the great and lesser apes remain unclear. It is here documented that area 10 also forms the frontal pole of chimpanzee, bonobo, orangutan, and gibbon brains. Imaging techniques and stereological tools are used to characterize this area across species and provide preliminary estimates of its absolute and relative size. Area 10 has similar cytoarchitectonic features in the hominoid brain, but aspects of its organization vary slightly across species, including the relative width of its cortical layers and the space available for connections. The cortex forming the frontal pole of the gorilla appears highly specialized, while area 10 in the gibbon occupies only the orbital sector of the frontal pole. Area 10 in the human brain is larger relative to the rest of the brain than it is in the apes, and its supragranular layers have more space available for connections with other higher-order association areas. This suggests that the neural substrates supporting cognitive functions associated with this part of the cortex enlarged and became specialized during hominid evolution. Am J Phys Anthropol 114:224-241, 2001. [C] 2001 Wiley-Liss, Inc. KEY WORDS frontal pole; brain evolution; cytoarchitecture; brain mapping; stereology; hominoid; hominid

The understanding of biological variation within and between the currently recognized African apes extant species (Pan paniscus, Pan troglodytes and Gorilla gorilla) is a prerequisite for the testing of hypotheses regarding early hominid evolution. The C2000 software provides a computational model describing and analysing facial evolutionary and developmental changes. It was used to generate both three-dimensional imagery and model of osteodental maxillo-facial structures in extant chimpanzees, gorillas and some fossil hominids. An invariant maxillo-facial model of reference was observed in immature and adult extant humans from genetically distinct populations. Clear cut differences were found between the African ape species whereas the geometric model appeared stable during development within each taxon. Importantly, the differences between the two chimpanzee species identified so far, appeared to be as profound than the differences between, on the one hand, these chimpanzee species considered separately, and, on the other hand, gorillas. It was possible to apply this method to some fossil hominids even if some of them were incompletely preserved.

The semicircular canals of the inner ear scale with body mass, with different vertebrate taxa showing similar allometric exponents. Taking this scaling effect into account, the canals of extant great apes are smaller-arced than those of non-hominid primates. Given that canal arc size appears to correlate with aspects of a species' locomotor repertoire, the question arises whether the smaller canal size of the great apes reflects shared behaviour, perhaps related to their large body size, or simply represents shared phylogeny. It is interesting in this context to examine whether non-hominid primates of great ape size show the smaller canal size as well. One of the very few species for which this can be assessed is Theropithecus oswaldi. During the Plio-Pleistocene this cercopithecid doubled in body mass leading to later representatives of female gorilla size. The bony labyrinths of six T. oswaldi specimens (Upper Burgi & Okote Members, Koobi Fora Formation, Upper Bed II & Bed IV, Olduvai Gorge) were imaged using CT, and their semicircular canal sizes were measured. The results suggest that with the dramatic temporal increase in body mass the canals actually became smaller-arced. Early baboon-sized T. oswaldi has baboon-sized canals, whereas later female gorilla-sized specimens have great ape-sized canals. This intraspecific shift in canal size from the non-hominid to the great ape regression suggests that the smaller canal size of great apes may not just reflect shared phylogeny but also some, probably size-related, aspects of locomotor behaviour, that perhaps characterized late T. oswaldi as well.

Major components of the frontal lobe like the dorsal, mesial and orbital sectors are associated with distinct cognitive attributes. It is here hypothesized that some species-specific adaptations in the behavior of the great apes may be reflected in the relative size of these sectors including the relative size of their gray and white matter. MR scans of the living brain of three bonobos, six chimpanzees, two gorillas and four orangutans were used to estimate the absolute and relative volumes of a) the frontal cortex (FC) and its immediately underlying white matter (WM), and b) the dorsal, mesial and orbital cortices of FC and the white matter underlying each of these cortical regions. Across species the dorsal sector has the lowest ratio of cortex to white matter, followed by the mesial and orbital sectors. The dorsal cortex occupies the largest part of FC (55% to 60%) and the mesial cortex makes up 26%-30% across the great ape species. The orbital cortex forms 15% to 17% of FC in the African apes, but only 10% of FC in the orangutans. Orangutan individual relative values of the orbital cortex do not overlap with individual values of the rest of the apes. The mean ratio of FC to WM is larger in gorillas and orangutans. Individual values overlap across the hominoid species, but most bonobos and chimpanzees have a lower FC to WM ratio than other individual apes. The orbital sector of the frontal lobe is involved in emotional responses to social stimuli and the present results confirm our earlier observations regarding the small size of this part of the brain in orangutans. The present findings also suggest that bonobos and chimpanzees may have increased interconnectivity between closely related areas in the frontal lobe.

Enlargement of the occipital marginal (O/M) venous sinus system has been used as a phylogenetic character to argue for the affinities of Australopithecus afarensis and the 'robust' australopithecines. However, since reports in the literature differ with regard to the frequency of O/M sinuses in great apes, the phylogenetic significance of this character is unclear. The present study was undertaken to determine the range of variability of O/M sinus morphology in the extant African great apes. Endocasts of Pan troglodytes (M=10; F=6), Pan paniscus (M=16; F=15) and Gorilla gorilla (M=22; F=13) from Holloway's collection were included in the sample. Each endocast was examined for the presence or absence of a visible O/M sinus. In addition, if judged to be present, the size of the O/M sinus system was compared to that of the transverse-sigmoid system. Among African great apes (n=82), a detectable O/M (or occipital) sinus occurred in 50% of cases (P. troglodytes = 50%; P. paniscus = 35%; G. gorilla = 63%). However, in not a single case did the O/M sinus system appear to be 'enlarged', i.e., equal or dominant to the transverse-sigmoid system. These results extend prior reports of O/M sinuses in the African great apes based on different methods (e.g., Kimbel, 1984; Falk, 1986). Our results support Kimbel's (1984) conclusion, based on observations of the endocranium through the foramen magnum, that enlarged O/M sinuses are highly uncommon among Pan and Gorilla. The use of different criteria for assessment of O/M sinus size may be responsible for the present disagreement. These issues will be discussed.

The supraorbital region is often used in phylogenetic analyses of fossil and extant hominoids. While there is general agreement regarding the distribution of these character states among the living apes, fossil taxa are the focus of considerable debate. Dryopithecus, for example, is described by some as having a supraorbital torus; others suggest a similarity to the costae found in Pongo. Fueling this debate is a reliance on verbal description for the diagnosis of these character states. Hominoid supraorbital morphology is typically described as a rim (Hylobates), costa (Pongo), or torus (Gorilla and Pan). Traditional morphometric approaches have been used to quantify this region, but fail to incorporate its complex 3D morphology. This study used a geometric morphometric approach to analyze the supraorbital morphologies of extant and fossil hominoids. Papio was also included as an outgroup. Several landmarks and a single ridge curve were collected from extant specimens using a Microscribe 3DX mechanical three-dimensional digitizer. Coordinate data from all specimens were superimposed using a generalized Procrustes analysis. The resulting fitted coordinates were then analyzed using multivariate statistical methods, including PCA, CVA, and DA. These steps were repeated, using only the left side of this region, in order to incorporate specimens of Dryopithecus (IPMC 18000) and Sivapithecus (GSP 15000). Results from analyses of extant taxa show a clear separation between Papio and the hominoids. Among hominoids, great apes clustered apart from Hylobates; Gorilla and Pan were the most similar, with some overlap in range. No significant size correlation was found. Analysis of the fossil specimens showed clear affinities between Sivapithecus and Pongo, and between Dryopithecus and the African apes. While the former is not surprising, results from Dryopithecus offer additional support for grouping this taxon with the African ape clade. This research was supported by NSF grants to NYCEP (DIR 91-13609) and the AMNH (ACI 99-82351).

The partial Australopithecus afarensis skeleton A.L. 288-1 ('Lucy') has played an important role in the assessment of the locomotor repertoire of early hominins. Specifically, it has been argued that 'Lucy' possessed shorter femora than Homo, making her a less efficient biped than members of our own genus. This study compares 'Lucy' to a sample of African ape (n=53) and recent human (n=731) skeletons. Skeletal trunk height (STH), tibial length (TL) and radius length (RL) were predicted for 'Lucy.' TL was predicted from human and nonhuman hominoid regressions; RL was predicted from an ape regression only, since forearm foreshortening occurs relatively late in human evolution (Asfaw et al., 1999). Predicted TL, RL, and their associated 95% confidence limits were then included with femoral head diameter (FH), femoral length (FL), humeral length (HL) and STH in a PCA. Results indicate that in body shape 'Lucy' is more similar to African apes than to humans. Her ape-like affinities are largely the result of two phenomena: 1) a long RL, and 2) the allometric consequences of small body size. Bivariate allometric plots reveal that A.L. 288-1 has an FL (and HL) of the length expected for a human of her body mass. Humans show slight positive allometry in FL to body mass - unusual, since most mammals, including the African apes, exhibit a subisometric relationship of FL to body mass. As Franciscus and Holliday (1992) first suggested, 'Lucy' lies near the confluence of the ape and human lines, and thus cannot resolve the issue of lower limb elongation in Australopithecus. However, larger specimens referred to A. ('Paranthropus') boisei fall clearly among early and recent Homo, and not among African apes. Thus, it is predicted that larger Australopithecus individuals, even members of a species as early as afarensis, will tend to have relatively longer femora than both African apes and smaller congenerics such as 'Lucy'. Data collection supported in part by NSF (#SBR9321339) and the L.S.B. Leakey Foundation.