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A 3D quantitative comparison of trapezium and trapezoid relative articular and nonarticular surface areas in modern humans and great apes.

The structure and functions of the modern human hand are critical components of what distinguishes Homo sapiens from the great apes (Gorilla, Pan, and Pongo). In this study, attention is focused on the trapezium and trapezoid, the two most lateral bones of the distal carpal row, in the four extant hominid genera, representing the first time they have been quantified and analyzed together as a morphological-functional complex. Our objective is to quantify the relative articular and nonarticular surface areas of these two bones and to test whether modern humans exhibit significant shape differences from the great apes, as predicted by previous qualitative analyses and the functional demands of differing manipulative and locomotor strategies. Modern humans were predicted to show larger relative first metacarpal and scaphoid surfaces on the trapezium because of the regular recruitment of the thumb during manipulative behaviors; alternatively, great apes were predicted to show larger relative second metacarpal and scaphoid surfaces on the trapezoid because of the functional demands on the hands during locomotor behaviors. Modern humans were also expected to exhibit larger relative mutual joint surfaces between the trapezoid and adjacent carpals than do the great apes because of assumed transverse loads generated by the functional demands of the modern human power grip. Using 3D bone models acquired through laser digitizing, the relative articular and nonarticular areas on each bone are quantified and compared. Multivariate analyses of these data clearly distinguish modern humans from the great apes. In total, the observed differences between modern humans and the great apes support morphological predictions based on the fact that this region of the human wrist is no longer involved in weight-bearing during locomotor behavior and is instead recruited solely for manipulative behaviors. The results provide the beginnings of a 3D comparative standard against which further extant and fossil primate wrist bones can be compared within the contexts of manipulative and locomotor behaviors.

Anatomy, Comparative↗

Divergence of ape and human monoamine oxidase A gene promoters: comparative analysis of polymorphisms, tandem repeat structures and transcriptional activities on reporter gene expression.

A variable number of tandem repeats (VNTR) polymorphism based on a 30-bp unit have been reported in the promoter region of the human monoamine oxidase A gene (MAOA). Human VNTRs have been shown to affect transcriptional activity, and some reports suggest that VNTR polymorphisms are associated with psychoneurological disorders. VNTR polymorphism has also been reported in the ape MAOA promoter but the transcriptional activities of the alleles remain to be determined. In the present study, we sequenced the 1.3-kb promoter region of ape MAOA and compared the transcriptional activities of ape MAOA promoter sequences with those of humans. All apes examined were polymorphic in the region corresponding to the human VNTR and two, four, three, and two alleles were found in chimpanzees, gorillas, orangutans, and gibbons, respectively. VNTR repeat structures in gorillas, orangutans, and gibbons were considerably different from those in humans and chimpanzees. In a human neuroblastoma cell line, most of the ape sequences that had a short repeat length (12bp or 18bp) exhibited higher promoter activity than a human 3-repeat sequence with a 30-bp repeat length. However, an intra-species difference dependent on the repeat number was not observed among the ape alleles examined.

Animals↗

Miocene hominoid craniofacial morphology and the emergence of great apes.

The initial cladogenic event between Hominoidea (apes, including humans) and Cercopithecoidea (Old World monkeys) consisted primarily of changes in the craniofacial region. These changes, seen in taxa commonly known as victoriapithecids and proconsulids, arose in a mosaic fashion. The divergence in the postcranium was more subtle; there are strong suggestions that apes initially adopted a tail-less pronograde arboreal quadrupedalism, while cercopithecoids became better adapted to a more terrestrial lifestyle. Recent phylogenetic analysis suggests that gibbons (Hylobates) have reversed derived craniofacial characters autapomorphically, contradicting the interpretation that the origin of apes sensu stricto coincides with the emergence of suspensory adaptations. The suspensory postcranium evolved later and appeared first in Eurasia; recent palaeobiogeographic reconstructions suggest that suspensory apes subsequently re-colonized Africa, as suggested nearly thirty years ago on neontological grounds. To test whether these two models of hominoid evolution are compatible, catarrhine craniofacial and postcranial traits, including those from Eurasian fossils, were subjected to parsimony analysis. The results demonstrate a mosaic pattern of derived characters, with gibbons reversing some traits of the face, which suggests their derivation from a 'great ape' face. Combined with the palaeobiogeography, a much longer, step-wise transition from primitive catarrhines to extant great apes than previously envisioned is supported. The pattern of craniofacial change is difficult to interpret in functional/adaptational terms, but the origin of brachiation may have arisen through character displacement due to competition with the emerging modern Old World monkey radiation in Eurasia.

Animals↗

Trans-complementation by human apurinic endonuclease (Ape) of hypersensitivity to DNA damage and spontaneous mutator phenotype in apn1-yeast.

Abasic (AP) sites in DNA are potentially lethal and mutagenic. 'Class II' AP endonucleases initiate the repair of these and other DNA lesions. In yeast, the predominant enzyme of this type is Apn1, and its elimination sensitizes the cells to killing by simple alkylating agents or oxidants, and raises the rate of spontaneous mutation. We investigated the ability of the major human class II AP endonuclease, Ape, which is structurally unrelated to Apn1, to replace the yeast enzyme in vivo. Confocal immunomicroscopy studies indicate that approximately 25% of the Ape expressed in yeast is present in the nucleus. High-level Ape expression corresponding to approximately 7000 molecules per nucleus, equal to the normal Apn1 copy number, restored resistance to methyl methanesulfonate to near wild-type levels in Apn1-deficient (apn1-) yeast. Ape expression in apn1- yeast provided little protection against H2O2 challenges, consistent with the weak 3'-repair diesterase activity of the human enzyme. Ape expression at approximately 2000 molecules per nucleus reduced the spontaneous mutation rate of apn1- yeast to that seen for wild-type cells. Because Ape has a powerful AP endonuclease but weak 3'-diesterase activity, these findings indicate that endogenously generated AP sites can drive spontaneous mutagenesis.

DNA Damage↗

Morphological analysis of the hindlimb in apes and humans. II. Moment arms.

Flexion/extension moment arms were obtained for the major muscles crossing the hip, knee and ankle joints in the orang-utan, gibbon, gorilla (Eastern and Western lowland) and bonobo. Moment arms varied with joint motion and were generally longer in proximal limb muscles than distal limb muscles. The shape of the moment arm curves (i.e. the plots of moment arm against joint angle) differed in different hindlimb muscles and in the same muscle in different subjects (both in the same and in different ape species). Most moment arms increased with increasing joint flexion, a finding which may be understood in the context of the employment of flexed postures by most non-human apes (except orang-utans) during both terrestrial and arboreal locomotion. When compared with humans, non-human great apes tended to have muscles better designed for moving the joints through large ranges. This was particularly true of the pedal digital flexors in orang-utans. In gibbons, the only lesser ape studied here, many of the moment arms measured were relatively short compared with those of great apes. This study was performed on a small sample of apes and thus differences noted here warrant further investigation in larger populations.

Animals↗

Structural analysis of the genomes of gibbon ape and woolly monkey leukosis viruses.

Infectious retroviruses have been isolated from gibbon apes and a woolly monkey. Previous studies have shown that these isolates share some antigenic determinants and that they exhibit partial nucleic acid homology. To further define the relationships in this group of viruses, we compared the RNAs of the viruses of the woolly monkey-gibbon ape class by two-dimensional polyacrylamide gel electrophoresis of the large RNase T1-resistant oligonucleotides. The degree of sequence identity between the RNAs was determined by the similarity of the fingerprint patterns and in some cases by partial sequence analysis of individual oligonucleotides. This technique permitted us to determine the degree of sequence identity in related RNA species. These studies showed that as much as 80% of the genomes of gibbon ape leukosis virus-Halls' Island and gibbon ape leukosis virus-brain could be identical. The other viruses, simian sarcoma-associated virus, gibbon ape leukosis virus-Thailand, and gibbon ape leukosis virus-San Francisco, showed an extensive but somewhat lower degree of sequence identity (between 40 to 60% of the genomes.

Animals↗

Prevalence and etiology of linear enamel hypoplasia in monkeys and apes from Asia and Africa.

Ninety-seven specimens of sympatric monkeys and apes from East Malaysia and 115 monkeys and apes from West Africa are examined in order to evaluate the magnitude and nature of the great ape-monkey linear enamel hypoplasia (LEH) 'dichotomy'. This study demonstrates that great apes from both regions have a higher incidence of LEH and repetitive LEH than do gibbons and monkeys. However, the authors find that the dichotomy is not as clear-cut as previous research suggests, since some monkey samples exhibit high LEH frequencies. The authors evaluate the potential influence of great ape-monkey differences in crown height on this dichotomy. They show that canine crown height variation is weakly associated with LEH variation. Differences between monkeys and great apes in their crown formation spans and in their experience of environmental stress may be more likely causes of the dichotomy.

Africa↗

Size and scaling in the mandible of living and extinct apes.

The purpose of this study is to fill a gap in our knowledge of dietary and allometric determinants of masticatory function and mandibular morphology in major catarrhine clades. To extend the implications of previous work on variation in mandibular form and function in other primates, a scaling analysis was performed on 20 extinct and 7 living non-cercopithecoid catarrhines or 'dental apes'. Results of allometric comparisons indicate that for a given jaw length, larger apes exhibit significantly more robust corpora and symphyses than smaller forms. This appears linked to size-related increases in dietary toughness and/or hardness, which in turn causes elevated mandibular loads and/or greater repetitive loading during unilateral mastication. Larger-bodied dental apes also display more curved symphyses, which also explains the positive allometry of symphysis width and height. In apes, proconsulids often evince more robust jaws while all hylobatids, Pan and Dryopithecus laietanus possess more gracile cross sections. In propliopithecids, Aegyptopithecus is always more robust than Propliopithecus. In proconsulids, Rangwapithecus and Micropithecus commonly exhibit more robust jaws whereas Dendropithecus and especially Simiolus are more gracile. Most of the larger taxa are folivorous and/or hard-object frugivorous pongids with relatively larger dentaries. Though apes have relatively wider corpora than cercopithecines due to greater axial twisting of the corpora during chewing, they are otherwise alike in robusticity levels. Smaller apes are similar to cercopithecines in evincing a relatively high degree of symphyseal curvature, while larger taxa are like colobines in having less curvature. Larger pongids resemble or even exceed colobine jaw proportions and thus appear to converge on colobines in terms of the mechanical properties of their diets.

Animals↗

Sequencing the orthologs of human autosomal forensic short tandem repeats provides individual- and species-level identification in African great apes.

BACKGROUND: Great apes are a global conservation concern, with anthropogenic pressures threatening their survival. Genetic analysis can be used to assess the effects of reduced population sizes and the effectiveness of conservation measures. In humans, autosomal short tandem repeats (aSTRs) are widely used in population genetics and for forensic individual identification and kinship testing. Traditionally, genotyping is length-based via capillary electrophoresis (CE), but there is an increasing move to direct analysis by massively parallel sequencing (MPS). An example is the ForenSeq DNA Signature Prep Kit, which amplifies multiple loci including 27 aSTRs, prior to sequencing via Illumina technology. Here we assess the applicability of this human-based kit in African great apes. We ask whether cross-species genotyping of the orthologs of these loci can provide both individual and (sub)species identification. RESULTS: The ForenSeq kit was used to amplify and sequence aSTRs in 52 individuals (14 chimpanzees; 4 bonobos; 16 western lowland, 6 eastern lowland, and 12 mountain gorillas). The orthologs of 24/27 human aSTRs amplified across species, and a core set of thirteen loci could be genotyped in all individuals. Genotypes were individually and (sub)species identifying. Both allelic diversity and the power to discriminate (sub)species were greater when considering STR sequences rather than allele lengths. Comparing human and African great-ape STR sequences with an orangutan outgroup showed general conservation of repeat types and allele size ranges. Variation in repeat array structures and a weak relationship with the known phylogeny suggests stochastic origins of mutations giving rise to diverse imperfect repeat arrays. Interruptions within long repeat arrays in African great apes do not appear to reduce allelic diversity. CONCLUSIONS: Orthologs of most human aSTRs in the ForenSeq DNA Signature Prep Kit can be analysed in African great apes. Primer redesign would reduce observed variability in amplification across some loci. MPS of the orthologs of human loci provides better resolution for both individual and (sub)species identification in great apes than standard CE-based approaches, and has the further advantage that there is no need to limit the number and size ranges of analysed loci.

Animals↗

Lack of malaria parasite transmission between apes and humans in Gabon.

The International Center for Medical Research (CIRMF) is located in an area highly endemic for malaria in southeastern Gabon, where humans and apes (gorillas and chimpanzees) are living in the same geographic area. The presence of the CIRMF primate center housing apes (59 chimpanzees and nine gorillas in 1994) within the city of Franceville provided an opportunity to investigate the capability of cross-transmission of malaria species from humans to apes. The main vector of human malaria, Anopheles gambiae, was found in the primate center and in a nearby populated area of Franceville. Despite high malaria transmission in humans of both Plasmodium falciparum and P. malariae (mean of 43% cumulative prevalence in schoolchildren), none of the apes were found infected with plasmodia during a six-month investigation. However, low antibody levels against sporozoite and blood stages of both P. falciparum and P. malariae were detected in a few chimpanzees and gorillas. These results demonstrate that only rarely would apes be bitten in the field by mosquitoes infected with human malaria parasites. In the case of infection proven by serology, we did not find any evidence that blood-stage malaria parasites were able to the gametocyte stage. The absence of any established malaria transmission cycle within the primate colony of CIRMF indicates that apes cannot be considered as animal reservoirs for human malaria parasites in this environment.

Adolescent↗

Anthrax in Western and Central African great apes.

During the period of December 2004 to January 2005, Bacillus anthracis killed three wild chimpanzees (Pan troglodytes troglodytes) and one gorilla (Gorilla gorilla gorilla) in a tropical forest in Cameroon. While this is the second anthrax outbreak in wild chimpanzees, this is the first case of anthrax in gorillas ever reported. The number of great apes in Central Africa is dramatically declining and the populations are seriously threatened by diseases, mainly Ebola. Nevertheless, a considerable number of deaths cannot be attributed to Ebola virus and remained unexplained. Our results show that diseases other than Ebola may also threaten wild great apes, and indicate that the role of anthrax in great ape mortality may have been underestimated. These results suggest that risk identification, assessment, and management for the survival of the last great apes should be performed with an open mind, since various pathogens with distinct characteristics in epidemiology and pathogenicity may impact the populations. An animal mortality monitoring network covering the entire African tropical forest, with the dual aims of preventing both great ape extinction and human disease outbreaks, will create necessary baseline data for such risk assessments and management plans.

Animals↗

A new southern limit for the distribution of African great apes: sympatric western lowland gorilla (Gorilla gorilla gorilla) and central chimpanzee (Pan troglodytes troglodytes) confirmed in Mayombe National Park, Angola.

The distribution of African great apes has remained unconfirmed regarding their southern limit, particularly on the western side of the continent. IUCN maps include the Mayombe forest of Angola as part of the estimated distribution of western lowland gorillas (Gorilla gorilla gorilla) and central chimpanzees (Pan troglodytes troglodytes). However, until now no published evidence-based records had confirmed the continued presence of both species. The Mayombe forest is a key biodiversity hotspot and a potentially important stronghold for the conservation of great ape populations in Africa. Here, we report the first systematic evidence of both species in the Mayombe National Park, Cabinda, Angola. In 2023, a grid of camera traps was systematically deployed, producing the first visual records of gorillas and chimpanzees. Building on these findings, in 2024, a pilot survey including ad libitum field observations was carried out along exploratory trails to maximise data collection. The combination of these records identified a hotspot of great ape activity where six transects were established, and systematic direct and indirect evidence was documented. Chimpanzees were recorded more times across a broader range of evidence categories, while gorillas appeared less and seemed more spatially restricted. Notably, both species were detected at overlapping sites but never simultaneously, indicating sympatric coexistence with spatio-temporal partitioning. These findings confirm the southernmost predicted distribution of both species for this part of Africa, filling critical gaps in the understanding of great ape evolution and biogeography, and providing a baseline for the first demographic and ecological census of great apes in Angola.

Animals↗

Catastrophic ape decline in western equatorial Africa.

Because rapidly expanding human populations have devastated gorilla (Gorilla gorilla) and common chimpanzee (Pan troglodytes) habitats in East and West Africa, the relatively intact forests of western equatorial Africa have been viewed as the last stronghold of African apes. Gabon and the Republic of Congo alone are thought to hold roughly 80% of the world's gorillas and most of the common chimpanzees. Here we present survey results conservatively indicating that ape populations in Gabon declined by more than half between 1983 and 2000. The primary cause of the decline in ape numbers during this period was commercial hunting, facilitated by the rapid expansion of mechanized logging. Furthermore, Ebola haemorrhagic fever is currently spreading through ape populations in Gabon and Congo and now rivals hunting as a threat to apes. Gorillas and common chimpanzees should be elevated immediately to 'critically endangered' status. Without aggressive investments in law enforcement, protected area management and Ebola prevention, the next decade will see our closest relatives pushed to the brink of extinction.

Animals↗

Brain structure variation in great apes, with attention to the mountain gorilla (Gorilla beringei beringei).

This report presents data regarding the brain structure of mountain gorillas (Gorilla beringei beringei) in comparison with other great apes. Magnetic resonance (MR) images of three mountain gorilla brains were obtained with a 3T scanner, and the volume of major neuroanatomical structures (neocortical gray matter, hippocampus, thalamus, striatum, and cerebellum) was measured. These data were included with our existing database that includes 23 chimpanzees, three western lowland gorillas, and six orangutans. We defined a multidimensional space by calculating the principal components (PCs) from the correlation matrix of brain structure fractions in the well-represented sample of chimpanzees. We then plotted data from all of the taxa in this space to examine phyletic variation in neural organization. Most of the variance in mountain gorillas, as well as other great apes, was contained within the chimpanzee range along the first two PCs, which accounted for 61.73% of the total variance. Thus, the majority of interspecific variation in brain structure observed among these ape taxa was no greater than the within-species variation seen in chimpanzees. The loadings on PCs indicated that the brain structure of great apes differs among taxa mostly in the relative sizes of the striatum, cerebellum, and hippocampus. These findings suggest possible functional differences among taxa in terms of neural adaptations for ecological and locomotor capacities. Importantly, these results fill a critical gap in current knowledge regarding great ape neuroanatomical diversity.

Animals↗

Variability of Broca's area homologue in African great apes: implications for language evolution.

The cortical circuits subserving neural processing of human language are localized to the inferior frontal operculum and the posterior perisylvian region. Functional language dominance has been related to anatomical asymmetry of Broca's area and the planum temporale. The evolutionary history of these asymmetric patterns, however, remains obscure. Although testing of hypotheses about the evolution of language areas requires comparison to homologous regions in the brains of our closest living relatives, the great apes, to date little is known about normal interindividual variation of these regions in this group. Here we focus on Brodmann's area 44 in African great apes (Pan troglodytes and Gorilla gorilla). This area corresponds to the pars opercularis of the inferior frontal gyrus (IFG), and has been shown to exhibit both gross and cytoarchitectural asymmetries in humans. We calculated frequencies of sulcal variations and mapped the distribution of cytoarchitectural area 44 to determine whether its boundaries occurred at consistent macrostructural landmarks. A considerable amount of variation was found in the distribution of the inferior frontal sulci among great ape brains. The inferior precentral sulcus in particular was often bifurcated, which made it impossible to determine the posterior boundary of the pars opercularis. In addition, the distribution of Brodmann's area 44 showed very little correspondence to surface anatomy. We conclude that gross morphologic patterns do not offer substantive landmarks for the measurement of Brodmann's area 44 in great apes. Whether or not Broca's area homologue of great apes exhibits humanlike asymmetry can only be resolved through further analyses of microstructural components.

Africa↗

Postcranial functional morphology of Morotopithecus bishopi, with implications for the evolution of modern ape locomotion.

The large-bodied hominoid from Moroto, Uganda has until recently been known only from proconsulid like craniodental remains and some vertebrae with modern ape like features. The discovery of two partial femora and the glenoid portion of a scapula demonstrates that the functional anatomy of Morotopithecus differed markedly from other early and middle Miocene hominoids. Previous studies have consistently associated the vertebral remains with a short, stiff back and with orthograde postures. Although the proximal femur more closely resembles the femora of monkeys than of apes and suggests a moderate degree of hip abduction, the distal femur resembles those of extant large bodied apes and suggests a varied loading regime and an arboreal repertoire that may have included substantial vertical climbing. The femoral shaft displays uniformly thick cortical bone, beyond the range of thickness seen in extant primates, and signifies higher axial loading than is typical of most extant primates. The glenoid fossa is broad and uniformly curved as in extant suspensory primates. Overall, Morotopithecus is reconstructed as an arboreal species that probably relied on forelimb-dominated, deliberate and vertical climbing, suspension and quadrupedalism. Morotopithecus thus marks the first appearance of certain aspects of the modern hominoid body plan by at least 20 Ma. If the suspensory and orthograde adaptations linking Morotopithecus to extant apes are synapomorphies, Morotopithecus may be the only well-documented African Miocene hominoid with a close relationship to living apes and humans.

Animals↗

Conservation of human Y chromosome sequences among male great apes: implications for the evolution of Y chromosomes.

Nine newly described single-copy and low-copy-number genomic DNA sequences isolated from a flow-sorted human Y chromosome library were mapped to regions of the human Y chromosome and were hybridized to Southern blots of male and female great ape genomic DNAs (Gorilla gorilla, Pan troglodytes, Pongo pygmaeus). Eight of the nine sequences mapped to the euchromatic Y long arm (Yq) in humans, and the ninth mapped to the short arm or pericentromeric region. All nine of the newly identified sequences and two additional human Yq sequences hybridized to restriction fragments in male but not female genomic DNA from the great apes, indicating Y chromosome localization. Seven of these 11 human Yq sequences hybridized to similarly-sized restriction endonuclease fragments in all the great ape species analyzed. The five human sequences that mapped to the most distal subregion of Yq (deletion of which region is associated with spermatogenic failure in humans) were hybridized to Southern blots generated by pulsed-field gel electrophoresis. These sequences define a region of approximately 1 Mb on human Yq in which HpaII tiny fragment (HTF) islands appear to be absent. The conservation of these human Yq sequences on great ape Y chromosomes indicates a greater stability in this region of the Y than has been previously described for most anonymous human Y chromosomal sequences. The stability of these sequences on great ape Y chromosomes seems remarkable given that this region of the Y does not undergo meiotic recombination and the sequences do not appear to encode genes for which positive selection might occur.

Animals↗

Body orientation and face orientation: two factors controlling apes' behavior from humans.

A number of animal species have evolved the cognitive ability to detect when they are being watched by other individuals. Precisely what kind of information they use to make this determination is unknown. There is particular controversy in the case of the great apes because different studies report conflicting results. In experiment 1, we presented chimpanzees, orangutans, and bonobos with a situation in which they had to request food from a human observer who was in one of various attentional states. She either stared at the ape, faced the ape with her eyes closed, sat with her back towards the ape, or left the room. In experiment 2, we systematically crossed the observer's body and face orientation so that the observer could have her body and/or face oriented either towards or away from the subject. Results indicated that apes produced more behaviors when they were being watched. They did this not only on the basis of whether they could see the experimenter as a whole, but they were sensitive to her body and face orientation separately. These results suggest that body and face orientation encode two different types of information. Whereas face orientation encodes the observer's perceptual access, body orientation encodes the observer's disposition to transfer food. In contrast to the results on body and face orientation, only two of the tested subjects responded to the state of the observer's eyes.

Animals↗