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Skull of Catopithecus browni, an early tertiary catarrhine.

Fossil crania from quarry L-41, Fayum, Egypt, representing Catopithecus browni, a primate similar in size to callitrichids but with a catarrhine dental formula, provide the geologically earliest record of an anthropoidean skull. Catopithecus had postorbital closure developed to the stage seen in extant anthropoideans, with direct contact between zygomatic plate and maxillary tuber, isolating an anterior orbital fissure from the inferior orbital fissure. The auditory region also resembles that of later anthropoideans: The posterior carotid foramen is placed adjacent to the jugular fossa; a large promontory canal crosses the promontorium; and the annular ectotympanic is fused ventrally to the bulla. The incisors and canines show an assemblage of features found only among modern anthropoideans and adapoids. The face is characterized by a relatively deep maxilla, broad ascending wing of the premaxilla, and long nasal bones, yielding a moderate muzzle similar to that of Aegyptopithecus. The small braincase bears an anteriorly broad frontal trigon and a posteriorly developed sagittal crest. The mandibular symphysis is unfused even in mature adults. The encephalization quotient (EQ) probably falls within the range of Eocene prosimians, much lower than the EQs of Neogene anthropoideans.

Animals

Allometric patterns of cranial bone thickness in fossil hominids.

The interspecific allometry of five measures of total cranial bone thickness is examined in 10 extant catarrhine genera and two fossil hominid samples representing A. africanus and Asian H. erectus. Analysis of the modern sample shows that most interspecific variation in vault thickness can be accounted for by variation in body size. Correlation values are moderate to high (r = 0.75-0.98), and all variables exhibit positive allometry. The bone thickness: body mass relationship of modern humans broadly conforms with that of other primates. However, in the distribution of relative thickness throughout the skull, H. sapiens is distinguished by relative thickening of the parietal and extreme relative thinning of the temporal squama. The bone thickness: body mass relationship in the two early hominid species is examined using published mean body weight estimates generated from post-cranial predictor variables. A. africanus exhibits great similarity to modern humans in its relation to the catarrhine regression data and in the distribution of relative thickness throughout the skull. H. erectus also shows a modern human-like pattern in the distribution of its relative thickness; however, its bone thickness: body mass relationship is dissimilar to that displayed by all other taxa, including the other hominid species. On the basis of these results, it is suggested that the published body weight estimate assigned to H. erectus greatly underestimates actual mean body size for Asian members of this species.

Africa

Cercopithecid locomotion, support use, and support availability in the Tai Forest, Ivory Coast.

Habitat heterogeneity is widely theorized to be important in the evolution of Old World monkeys, yet the impact of architecturally distinct forest types on the positional repertoires of African monkeys is largely unknown. As part of a wider project, this study investigates how the locomotor behavior of five sympatric cercopithecids varies in structurally distinct forest areas. Fieldwork took place in the Tai Forest, Ivory Coast, from June 1993 to August 1994. Data were collected on Colobus badius, C. polykomos, C. verus, Cercopithecus diana, and C. campbelli ranging throughout a common forest mosaic. The behavior of adult females was sampled using an instantaneous time point scheme at 3 min time intervals. Vegetative differences within each 100 x 100 m grid cell used by all species were quantified. Further, the relative numbers of different sized substrates at 10 m intervals within the canopy were recorded in each cell sampled. Data indicate that consistency of locomotor behavior across forest types is maintained because most monkeys select the same set of preferred supports in both forest types. The conservative nature of Tai monkey locomotor behavior is discussed within the context of additional proximate and ultimate influences and constraints.

Animals

Evolution of human growth spurts.

This study investigates subadult growth spurts in a large sample of anthropoid primates, including humans. Analyses of body mass growth curves show that humans are not unique in the expression of female and male body mass growth spurts. Subadult growth spurts are observed in both New World and Old World anthropoid primates and are more common in males than in females. Allometric analyses of growth spurts indicate that many aspects of primate growth spurts are strongly correlated with species size. Small species tend not to exhibit growth spurts. Although male and female scaling patterns for velocity and size measures are comparable, scaling relations of variables that measure the timing of growth spurts differ by sex. These patterns can be related to sexual differences in life histories. Scaling analyses further show that humans do not depart substantially from patterns that describe other anthropoid primates. Thus, in relative terms, human growth spurts are not exceptional compared to this sample of primates. The long absolute delay in the initiation of the human growth spurt may be of substantial evolutionary importance and serves to distinguish humans from other primates. In essence, humans exhibit growth spurts that are comparable to other primates in many respects. However, human growth spurts are shifted to very late absolute ages.

Animals

Fluorescene in situ hybridization establishes homology between human and silvered leaf monkey chromosomes, reveals reciprocal translocations between chromosomes homologous to human Y/5, 1/9, and 6/16, and delineates an X1X2Y1Y2/X1X1X2X2 sex-chromosome system.

We employed in situ hybridization of chromosome-specific DNA probes ("chromosome painting") of all human chromosomes to establish homologies between the human and the silvered lead monkey karyotypes (Presbytis cristata 2n = 44). The 24 human paints gave 30 signals on the haploid female chromosome set and 34 signals on the haploid male chromosome set. This difference is due to a reciprocal translocation between the Y and an autosome homologous to human chromosome 5. This Y/autosome reciprocal translocation which is unique among catarrhine primates has produced a X1X2Y1Y2/X1X1X2X2 sex-chromosome system. Although most human syntenic groups have been maintained in the silvered leaf monkey chromosomes homologous to human chromosomes 14 and 15, 21 and 22 have experienced Robertsonian fusions. Further, the multiple FISH signals provided by libraries to human chromosomes 1/9, 6/16 indicate that these chromosomes have been split be reciprocal translocations. G-binding analysis shows three different forms of chromosome 1 (X2) which differ by a complex series of inversions in the 10 individuals karyotype. Comparisons with the hybridization patterns in hylobatids (gibbons and siamang) demonstrate that resemblances in chromosomal morphology and banding previously taken to indicate a special phylogenetic relationship between gibbons and colobines are due to convergence.

Animals

Volumetric comparisons in the cerebellar complex of anthropoids, with special reference to locomotor types.

Seven measurements in the cerebellar complex were completed on 45 individuals, including 26 species of anthropoids from Stephan's collection. These included 12 species of New World monkeys, 10 species of Old World monkeys, and Hylobates, Gorilla, Pan, and humans. The measurements were the volume of medial (fastigial) (CM), interpositus (globose and emboliform) (CI), and lateral (dentate) (CL) cerebellar nuclei, ventral pons (VPo), inferior olivary principal (OLIPr), and accessory (OLIAc) nuclei and vestibular nuclear complex (VES). The relative size of each nucleus was expressed in size indices based upon the allometric line obtained by the reduced major axis analysis. The indices of three cerebellar nuclei reflect the relative size of three longitudinal zones of the cerebellum. The cerebellar hemisphere-lateralis zone is represented by the CL indices, the vermis-medialis zone by the CM indices, and the pars intermedius-interpositus zone by the CI indices. The results show that the VPo and OLIPr indices are closely related to the CL indices. This lateral zone group of nuclei is the most progressively developed in humans, whereas the CM, CI, OLIAc, and VES are independent of the developmental trend manifest by the lateral zone group of nuclei. The indices are discussed in relation to the predominant locomotor pattern exhibited by a species. The size indices of arboreal quadrupeds show a development of all nuclei in the cerebellar complex. This is interpreted as indicating that arboreal monkeys live in complicated, discontinuous, three-dimensional space and need exceptional cerebellar capacity for each pattern of locomotion and positional behavior. Progressive development of the lateral zone group of nuclei only compared to other nuclei was recognizable in humans. This development is considered to be related not to bipedalism, but to versatile and coordinated finger movement, resulting after bipedalism was established. This cerebellar reorganization is also a prerequisite (Leiner et al. [1993] TINS 16: 444-447) for the evolution of human language. The differences between size indices of the nuclei of Macaca (= pronograde primate) and Ateles (= antipronograde one) are compared in relation to their vertical climbing kinesiological data.

Animals

Determinants of female dispersal in Thomas langurs.

Female dispersal occurs in a number of primate species. It may be related to: avoidance of inbreeding, reduction in food competition, reduction of predation risk, or avoidance of infanticide in combination with mate choice. Female dispersal was studied for a 5-year period in a wild population of Thomas langurs (Presbytis thomasi) that lived in one-male multi-female groups. Juvenile and adult individuals of both sexes were seen to disperse. Females appeared to transfer unhindered between groups, mostly from a larger group to a recently formed smaller one. They transferred without their infants and when not pregnant, and seemed to transfer preferentially during periods when extra-group males were harassing their group. During these inter-group encounters extra-group males seemed to try to commit infanticide. Thus, the timing of female transfer was probably closely linked to infanticide avoidance. Moreover, females seemed to transfer when the resident male of their group was no longer a good protector. The observations in the present study suggest that females transferred to reduce the risk of infanticide. Female dispersal may have another ultimate advantage as well, namely inbreeding avoidance. Due to the dispersal of both females and males the social organization of Thomas langurs was rather fluid. New groups were formed when females joined a male; male takeovers were not observed. Bisexual groups had only a limited life span, because all adult females of a bisexual group could emigrate. This pattern of unhindered female dispersal affects male reproductive strategies, and in particular it might lead to infanticidal behavior during inter-group encounters.

Animals

Thalassemia: recent insights into molecular mechanisms.

Recent advances in defining the molecular basis for the thalassemia syndromes are discussed. We now realize that the causes of the thalassemia phenotype are diverse and include gene deletions, nuclear RNA processing defects, nonsense mutations, fusion genes, termination codon mutants, and unstable globin chains.

Animals

Allometry of primate hair density and the evolution of human hairlessness.

Allometric analyses of hair densities in 23 anthropoid primate taxa reveal that increasingly massive primates have systematically fewer hairs per equal unit of body surface. Considering the absence of effective sweating in monkeys and apes, the negative allometry of relative hair density may represent an architectural adaptation to thermal constraints imposed by the decreasing ratios of surface area to volume in progressively massive primates. Judging by estimates of body volume, denudation of the earliest hominids should have progressed to a considerable extent prior to their shift from a forest to a grassland habitat during the Pliocene. We propose that, lacking a reflective coat of hair, the exploitation of eccrine sweating emerged as the primary mechanism for adaptation to the increased heat leads of man's new environment and permitted further reduction of the remnant coat to its present vestigial condition.

Animals

Sexual dimorphism and allometry in primate ossa coxae.

Five measurements were taken on the ossa coxae of 454 adult primates representing Ceboidea, Cercopithecoidea and Hominoidea. Sex differences in these variables and their relationships to overall body size and sexual dimorphism were tested by means of Student's T-test and regression analysis. The study attempts to clarify the nature of primate pelvic sexual dimorphism, including allometric effects, and more specifically, test the assertion made by Mobb and Wood (1977) that sexual dimorphism in body size in not an important determinant in pelvic sex differences. Variables that contribute to the size of the birth canal tend to be larger in females than males in all taxa studied except two. In these, Hylobates and Alouatta, there were no significant differences between the sexes for any of the five variables. In general, sexual dimorphism in variables contributing to the size of the birth canal was correlated (r approximately or equal to 0.8) with sexual dimorphism in body size. Furthermore, the coefficients of allometry underlying pelvic sex differences were shown to be moderately correlated (r approximately or equal to 0.5) with sexual dimorphism in size. The influence of other adaptive factors on primate pelvic sexual dimorphism are also briefly discussed.

Animals

The morphology and wear of the lingual notch in macaques and langurs.

Although interspecific differences in the relative development of molar occlusal features have been documented for most primate species, wear-related changes in these features are only beginning to be understood. In the present study, the notch between the metaconid and entoconid of M2 was examined in a skeletal sample of Macaca fascicularis, presbytis cristatus, and Presbytis rubicunda from the Museum of Comparative Zoology at Harvard University. Photogrammetric analyses yielded X, Y, and Z coordinates that were used to compute three angular measurements and two length measurements at the lingual notch. Statistical analyses of measurements from unworn dentitions indicated that the mesial slope of the entoconid is steeper than the distal slope of the metaconid in all three species. In addition, interspecific comparisons demonstrated that P. cristatus has the steepest lingual notch bordered by the largest molar shearing crests, while P. rubicunda and M. fascicularis have molar shearing crests of similar size, with P. rubicunda merely having higher cusps that are closer together than those of M. fascicularis. Finally, P. cristatus shows a smaller decrease in lingual cusp relief with wear than M. fascicularis, while P. cristatus and P. rubicunda probably show similar decreases in lingual cusp relief with wear. The differences in wear-related changes in lingual cusp relief between M. fascicularis and P. cristatus may well be related to the frugivorous/folivorous dietary differences between these species.

Animals

Ontogenetic and interspecific organ weight allometry in Old World monkeys.

The importance of allometry as an analytic tool is well recognized in the literature of primate morphology. However, a number of recent studies have illustrated how interpretive difficulties can arise when researchers confound different types of allometric data. Such confusion is due less to carelessness than to uncertainty about how different types of allometry are related. The present study examines the relationship between two types--ontogenetic and interspecific allometry--in the case of organ weight scaling in six species of Old World monkeys. Accepting the interpretation of interspecific allometry as a reflection of functional scaling constraints, the results of this analysis indicate how ontogenetic patterns have been modified in different-sized species to maintain compliance with these constraints. Specifically, for the heart and lungs it appears that vertical transpositions of individual species' ontogenies are dictated by isometric interspecific allometry, while in the case of the kidneys and liver, the relation of negative allometry across species entails alteration of the relative growth coefficients of the individual species. While these conclusions can at present only be applied to organ weight scaling, the approach of examining interspecific patterns in light of developmental differences between species should prove very helpful in our efforts to understand the phenomena of size and scaling.

Aging

Distribution of enamel on the incisors of Old World monkeys.

Longitudinal ground sections of 29 Old World monkey central lower incisors were studied histologically and metrically. Labiolingual incisor width tended to scale isometrically with body weight but with important deviations in relative incisor size, which appeared to be correlated with diet in accord with work by Hylander. Lower incisors of the predominantly folivorous colobine monkeys had a substantial layer of enamel on both lingual and labial aspects and consequently had blunt incisal edges. These teeth in both cercopithecins and papionins, which are omnivorous or frugivorous, had little or no enamel on the lingual aspect, resulting in sharp incisal edges. It is suggested that colobine incisors are used mainly in gripping and tearing leaves, whereas cercopithecine incisors are better adapted to cutting and scraping. Crown height showed a positive allometric relationship with overall incisor height, so that the tall incisors of papionins, especially Papio and Mandrillus, were more hypsodont than the shorter incisors of colobines and cercopithecins. This appears to be related to differences in the rates of incisor wear between the groups.

Animals

Nut-like oil seeds: food for monkeys, chimpanzees, humans, and probably ape-men.

The hypothetical hyperrobust australopithecine gnathic nutcracker adaptation is reexamined in light of ecobotanical information on edible wild nuts provided by the flora of tropical and subtropical Africa. The nut producing species are tree-forms. Those of the forest region do not as a rule produce fruits with edible mesocarps. In contrast, the woodland savanna species (particularly in the Zambezian region) characteristically provide an important whole fruit, i.e., a nutritious mesocarp in addition to edible oil-rich nut seeds. These fruits drop from the tree before they are fully mature and go through the final ripening phase on the ground. They are important seasonal foods for a variety of vertebrates, including primates, elephants, and antelope. Altogether the nuts exhibit a broad range of toughness values, measured here as strength under compression. The woodland nuts are not as tough (177-934 kg force, breaking load) as those of the tropical forest (192-1,673 kg force). The seed-predators of the woodland species include squirrels, baboons, warthogs, and parrots. Paleoecological analyses indicate that it was the woodland nuts that were probably available to Australopithecus boisei and A. robustus. Preliminary estimates of adult male gnathic nut-cracking capabilities suggest that A. boisei could have orally cracked a significant portion of the woodland nuts. In spite of this, ecobotanical data indicate that we can probably reject the hypothesis that these hominids were year-round gnathic nut-cracking specialists. Both the indirect and direct evidence support this conclusion.

Africa

Seed-eating by West African cercopithecines, with reference to the possible evolution of bilophodont molars.

Data on tooth use in eating fruits and seeds were collected on 12 West African monkeys representing five species of cercopithecines, Cercopithecus aethiops, Cercopithecus campbelli, Cercocebus atys, Erythrocebus patas, and Papio papio. Field observations and information in the published literature were used to select fruits for captive feeding trials. A total of over 27,000 tests were conducted to determine the preferences of the monkeys for 78 fruits. Data were collected on the selection of fruit parts, as well as tooth use, in eating 88 fruit species. All five monkey species had remarkably similar fruit part preferences. Seeds were eaten in 86% of the tested fruits and represent the fruit part most frequently eaten by all the tested monkeys. With few exceptions, molars were used to puncture and crush the seeds. It is suggested that the development of bilophodont molars might be an adaptation by Old World monkeys to seed predation. Given their large size relative to other arboreal frugivores, seed predation could provide a dietary niche for Old World monkeys.

Adaptation, Physiological

Absence of strongly kin-preferential behavior by adult female sooty mangabeys (Cercocebus atys).

The objective of this study was to test the hypothesis that kin-preferential behavior would be present in sooty mangabeys (Cercocebus atys), a species taxonomically close to baboons and macaques. The affiliative behavior of the adult female members of a large captive group of these mangabeys was analyzed to test this prediction. These females groomed, were approached by, were in proximity to, and were in contact with their kin significantly more than expected, but only when all kin were included in the analysis. Removal of only the mother-infant (less than 1 year) dyadic interactions removed all significant kin effects. Kin-preferential behavior was also absent in affiliative interactions among the adult females as a class. Affiliation between mothers and offspring significantly exceeded that for all other kinship categories (such as siblings, etc.), and affiliation with kin other than offspring did not differ from that with nonkin adults. In their interactions with nonkin, the adult females showed some preference (duration of grooming) for those adult females of similar age, an effect predicted by the intensity of interaction among members of the same age cohort during development. These similar-aged females may also be paternally related. In comparing these results with the existing literature on kin-preferential behavior, two conclusions may be reached: (1) age and degree of kinship are primary factors that must be considered in order to avoid the existing overgeneralization of the importance of kinship in primate social organization, and (2) the role and importance of affiliative behavior in kin-selection theory should perhaps be re-examined in light of questions raised by this study.

Animals

Functional assessment of subfamily variation in maxillomandibular morphology among Old World monkeys.

Among Old World monkeys, subfamily variation in maxillomandibular form is commonly attributed to divergent dietary and social behaviors. However, our knowledge of any musculoskeletal adaptations for gape in cercopithecines, and folivory in colobines, is incomplete. Such data are requisite to a more informed perspective on the evolutionary morphology of these taxa. Structural analyses of gape and biomechanical efficiency were applied to a representative sample of adult cercopithecids. Factors pertaining to the biomechanical scaling of cranial structures were evaluated with least-squares bivariate regression techniques. To assess subfamily differences in masticatory efficiency, analyses of covariance were made between relevant factors. Cercopithecines achieve increased gape and relative canine size mainly with strong positive allometry of the facial skull, combined with a larger gonial angle. Colobines possess a relatively long masseter lever arm and short facial skull, as well as an enlargened masseter-medial pterygoid complex. Subfamily differences in temporalis lever arm scaling are negligible. Biomechanical comparisons within and between subfamilies suggest that the mechanical advantage of the temporalis is relatively greater than that of the masseter, while the mechanical advantage of both muscles increases with face length. Evidence is presented to stress the need for adequate consideration of the dependent variable in allometric investigations of skull form.

Analysis of Variance