Growth of wild and laboratory born chimpanzees

The skeletal remains of a wild juvenile chimpanzee,Pan troglodytes verus, of known chronological age are measured and found to be smaller than laboratory born and fed juveniles of the same age. Other wild born immature skeletal materials of all the three subspecies ofPan troglodytes, including both known and estimated chronological ages, are also smaller than laboratory born chimpanzees when comparisons are made on corresponding age groups. Differences between wild and laboratory born chimpanzees are larger in the limb bones than in the cranium. Limb bones of laboratory individuals grow earlier than those of wild ones regardless of subspecies. Small limb bone size of wild chimpanzees is discussed in terms of life processes.     

Skeletal and dental growth and development in chimpanzees of the Taï National Park, Côte D'Ivoire

An extraordinary collection of 22 immature skeletons from Taï National Park, Côte d'Ivoire, has provided a rare opportunity to establish the timing of dental eruption and its correlation with skeletal fusion and morphometrics in wild chimpanzees of known chronological ages. Comparison of the immature Taï chimpanzees Pan troglodytes verus with adults from the same population show that sex differences in skeletal maturation apparently appear during the Juvenile II stage, about age 8. A few skeletons from other chimpanzee field sites conform to the dental and skeletal growth in Taï chimpanzees. The tempo of wild chimpanzee growth contrasts sharply with the rate demonstrated for captive individuals. Captive chimpanzees may mature as much as 3 years earlier. The ability to link physical development with field observations of immature chimpanzees increases our understanding of their life-history stages. These data provide an improved dataset for comparing the rates of growth among chimpanzees, Homo sapiens and fossil hominids.     

Comparison of diaphyseal growth between the Libben population and the Hamann-Todd chimpanzee sample

The differences in limb lengths and proportions between humans and chimpanzees are widely known. Humans have relatively shorter forelimbs and longer hind limbs than chimpanzees. Humans have a longer period of long bone formation than chimpanzees. Recent advances in estimating age-at-death in chimpanzees from their dentition have allowed us to reexamine long bone growth in chimpanzees using their skeletal remains and compare it with similar data for humans. A chronological normalization procedure allowing direct interspecific comparison of long bone growth is presented. The preadult chimpanzee sample (n = 43) is from the Hamann-Todd Osteological Collection from the Cleveland Museum of Natural History. All human specimens (n = 202) are from the late Woodland Libben Population currently housed at Kent State University. Relying on these cross-sectional data, we conclude that both species elongate their femora at similar absolute (length per unit time) but different relative (length relative to normalized dental age) rates. The species differ in the absolute growth rate of the humerus but share a common normalized rate of growth. Forelimb segment proportion differences between species are due to differential elongation rates of the segments. Hind limb diaphyseal proportions are the same in both species, which suggests that changes in segment length are proportional. Therefore, alternative developmental mechanisms exist in these closely related species which can produce changes in limb length. © 1996 Wiley-Liss, Inc.     

Skeletal pathology in Pan troglodytes schweinfurthii in Kibale National Park, Uganda

The ecological pressures shaping chimpanzee anatomy and behavior are the subject of much discussion in primatology and paleoanthropology, yet empirical data on fundamental parameters including body size, morbidity, and mortality are rare for wild chimpanzees. Here, we present skeletal pathology and body size data for 20 (19 crania, 12 postcrania) chimpanzees (Pan troglodytes schweinfurthii) from Kibale National Park, Uganda. We compare these data with other East African populations, especially Gombe National Park. Estimated body size for Kibale chimpanzees was similar to other East African populations and significantly larger than Gombe chimpanzees. The high rates of trauma and other skeletal pathology evident in the Kibale chimpanzee skeletons were similar to those in the Gombe skeletal sample. Much of the major skeletal trauma in the Kibale skeletons was attributable to falls, although other pathologies were noted as well, including apparent injuries from snares, degenerative arthritis, and minor congenital abnormalities.     

Isotopic ecology and dietary profiles of Liberian chimpanzees

An extensive suite of isotopic data (δ¹³C, δ¹⁵N, and δ¹⁸O) from enamel apatite and bone collagen of adult male and female wild chimpanzees establishes baseline values for Pan troglodytes verus in a primary rainforest setting. The Ganta chimpanzee sample derives from a restricted region in northern Liberia. Diet is examined using stable light isotopes at three life stages—infant, young juvenile, and adult—and developmental differences are investigated within and between individual males and females. The isotopic data are very homogeneous with few exceptions. Juvenile females show consistent enrichment in ¹³C relative to infants, while juvenile males do not. These data suggest that age at weaning may be more variable for male offspring who survive to adulthood than for female offspring. Alternatively, or additionally, the weaning diet of males and females may differ, with greater consumption of technologically extracted insects and/or nuts by young females. Metabolic differences, including growth and hormone-mediated responses, may also contribute to the observed variation.The Ganta chimpanzee data offer an independent and objective line of evidence to primatologists interested in the dietary strategies of the great apes and to paleoanthropologists seeking comparative models for reconstructing early hominin subsistence patterns. Despite the high diversity of dietary items consumed by chimpanzees, isotopic signatures of chimpanzees from a primary rainforest setting exhibit narrow ranges of variation similar to chimpanzees in more open habitats.     

Development of the visual preference of chimpanzees (<Emphasis Type="Italic">Pan troglodytes</Emphasis>) for photographs of primates: effect of social experience

In a study by Tanaka (2003) five captive chimpanzees preferred photographs of humans to those of chimpanzees. All the subjects were raised by humans and lived in captivity for many years. This suggests their preference might have developed through social experience. In this study examined this hypothesis by using three young chimpanzees raised by their mothers in a captive chimpanzee community. The young chimpanzees were tested four times before six years of age. I also tested eight adult chimpanzees that had been in captivity for more than 20 years. Each subject was presented with digitized color photographs of different species of primates on a touch-sensitive screen. The subjects received a food reward when they touched a photograph, irrespective of which photograph they touched. All the adult chimpanzees touched photographs of humans more frequently than those of any other species of primate. Two of the young chimpanzees showed no species preference before reaching 5 years of age, when they started to show preference for humans. The remaining young chimpanzee consistently preferred chimpanzees. These results suggest that development of visual preference of chimpanzees is affected by social experience during infancy.     

Patterns of size sexual dimorphism in Australopithecus afarensis: Another look

Size sexual dimorphism is one of the major components of morphological variation and has been associated with socioecology and behavioral variables such as mating patterns. Although several studies have addressed the magnitude and pattern of sexual dimorphism in Australopithecus afarensis, one of the earliest hominids, consensus has yet to be reached. This paper uses assigned resampling method, a data resampling method to estimate the magnitude of sexual dimorphism without relying on individual sex assessments, to examine the fossil hominid sample from Hadar. Two questions are asked: first, whether sexual dimorphism in a selected sample of skeletal elements of A. afarensis is the same as that in living humans, chimpanzees, or gorillas; and second, whether different skeletal elements reflect variation in sexual dimorphism in the same way. All possible metric variables were used as data in applying the method, including seven variables from three elements (mandibular canine, humerus, femur). Analyses show that A. afarensis is similar in size sexual dimorphism to gorillas in femoral variables, to humans in humeral variables, and to chimpanzees in canine variables. The results of this study are compatible with the hypothesis that the pattern of sexual dimorphism in A. afarensis is different from any that are observed in living humans or apes.     

Mortality rates among wild chimpanzees

In order to compare evolved human and chimpanzees' life histories we present a synthetic life table for free-living chimpanzees, derived from data collected in five study populations (Gombe, Ta?, Kibale, Mahale, Bossou). The combined data from all populations represent 3711 chimpanzee years at risk and 278 deaths. Males show higher mortality than females and data suggest some inter-site variation in mortality. Despite this variation, however, wild chimpanzees generally have a life expectancy at birth of less than 15 years and mean adult lifespan (after sexual maturity) is only about 15 years. This is considerably lower survival than that reported for chimpanzees in zoos or captive breeding colonies, or that measured among modern human hunter-gatherers. The low mortality rate of human foragers relative to chimpanzees in the early adult years may partially explain why humans have evolved to senesce later than chimpanzees, and have a longer juvenile period.     

Demographic parameters and life history of chimpanzees at Bossou, Guinea

Demographic parameters of wild chimpanzees at Bossou, Guinea, are presented and compared with those of other populations. The population size of Bossou chimpanzees has been stable over the last 26 years, except during two incidents of partial deforestation. The annual birth rate for a female (mean = 0.194, but 0.165 when the infant survived more than 4 years) and interbirth interval are not much different from those of other study sites. The primiparous age of Bossou chimpanzees, however, is far younger (mean = 10.9 years) than for all other known wild chimpanzee populations. The infant and juvenile survival rate is also the highest (female = 0.64, male = 0.52 for the first 8 years). As a result, the lifetime reproductive success of Bossou chimpanzees is estimated to be highest among long-term study sites. The rate of disappearance from Bossou dramatically increases during the adolescent stage, and most young chimpanzees disappear before or around maturation. Probably because the environmental capacity for chimpanzees at Bossou is at its limit, many young independent males, as well as females, have to disperse, though others may die. For chimpanzee alpha males of other populations, mature males may be needed as collaborators to defend resources. In the case of Bossou, however, a lack of adjacent groups, conspecific competitors, predators, and perhaps medium-sized mammals as prey for group hunting may eliminate this need of the alpha male for other males. The reasons why all males of other chimpanzee populations persist in being philopatric for life and maintain kin-related male bonds differing from most mammal species, including humans, are discussed.     

Fifty years of chimpanzee demography at Taronga Park Zoo

There has been a captive Pan troglodytes colony at Taronga Park Zoo in Sydney, Australia, since the mid-1930s. Demographic data on these animals were first analyzed in 1986; however, further information collected for 15 years since then is now available. The reproductive histories of 33 females in the colony have been recorded, and these data form the largest collection of captive chimpanzee data from a setting that has involved natural breeding conditions since the mid-1960s. These data were analyzed in conjunction with data from wild populations to establish the degree of variability present within chimpanzee reproductive parameters, and to identify which distinctive life history characteristics persist in well-provisioned, natural-fertility populations. The age at first birth for the chimpanzee females is 9.8 yr on average (n=16), which is 1-4.8 yr earlier than the average for wild populations. In line with this accelerated reproduction, birth intervals are also significantly shorter than those in noncaptive chimpanzee populations. The median birth interval for all surviving infants (based on a Kaplan-Meier survival analysis) is 49 months (n=43) compared to 62+ months for wild groups. At the same time, infant mortality remains high. The data confirm distinctive features of the life history of common chimpanzees, including later maturation, long birth intervals, a relatively invariant fertility schedule, and high juvenile mortality. However, aspects of both fertility and mortality are significantly related to social circumstances, indicating that in common chimpanzees, as in humans, life history characters may represent ecological and social adaptations rather than species-fixed characteristics.     

Reexamination of the African hominoid trichotomy with additional sequences from the primate beta-globin gene cluster.

Additional DNA sequence information from a range of primates, including 13.7 kb from pygmy chimpanzee (Pan paniscus), was added to data sets of beta-globin gene cluster sequence alignments that span the gamma 1, gamma 2, and psi eta loci and their flanking and intergenic regions. This enlarged body of data was used to address the issue of whether the ancestral separations of gorilla, chimpanzee, and human lineages resulted from only one trichotomous branching or from two dichotomous branching events. The degree of divergence, corrected for superimposed substitutions, seen in the beta-globin gene cluster between human alleles is about a third to a half that observed between two species of chimpanzee and about a fourth that between human and chimpanzee. The divergence either between chimpanzee and gorilla or between human and gorilla is slightly greater than that between human and chimpanzee, suggesting that the ancestral separations resulted from two closely spaced dichotomous branchings. Maximum parsimony analysis further strengthened the evidence that humans and chimpanzees share the longest common ancestry. Support for this human-chimpanzee clade is statistically significant at P = 0.002 over a human-gorilla clade or a chimpanzee-gorilla clade. An analysis of expected and observed homoplasy revealed that the number of sequence changes uniquely shared by human and chimpanzee lineages is too large to be attributed to homoplasy. Molecular clock calculations that accommodated lineage variations in rates of molecular evolution yielded hominoid branching times that ranged from 17-19 million years ago (MYA) for the separation of gibbon from the other hominoids to 5-7 MYA for the separation of chimpanzees from humans. Based on the relatively late dates and mounting corroborative evidence from unlinked nuclear genes and mitochondrial DNA for the close sister grouping of humans and chimpanzees, a cladistic classification would place all apes and humans in the same family. Within this family, gibbons would be placed in one subfamily and all other extant hominoids in another subfamily. The later subfamily would be divided into a tribe for orangutans and another tribe for gorillas, chimpanzees, and humans. Finally, gorillas would be placed in one subtribe with chimpanzees and humans in another, although this last division is not as strongly supported as the other divisions.     

Development of the hand and wrist bones in chimpanzees

Skeletal developmental of chimpanzees was studied cross-sectionally. By application of the TW2 method, we described the skeletal development of chimpanzees and compared their skeletal development with humans'. A development pattern of chimpanzees repeated accelerations and decelerations displaying “early-juvenile trough,” “pre-adolescent peak,” “mid-adolescent trough,” and “post-adolescent peak” in incremental curves. Sex differences in skeletal development are slower development in males during infant and early juvenile phases, and greater increment around the adolescent phase in males. Females are fully mature at younger ages than males, e.g. about one and a half years. In comparison with chimpanzees, humans have such characteristics as a longer slower period of juvenile development and a shorter spurt-like adolescent fast period which ends with full maturity.     

Metatarsal fusion pattern and developmental morphology of the Olduvai Hominid 8 foot: Evidence of adolescence

The morphology of the Olduvai Hominid (OH) 8 foot and the sequence of metatarsal epiphyseal fusion in modern humans and chimpanzees support the hypothesis that OH 8 belonged to an individual of approximately the same relative age as the OH 7 subadult, the holotype of Homo habilis. Modern humans and chimpanzees exhibit a variety of metatarsal epiphyseal fusion patterns, including one identical to that observed in OH 8 in which metatarsal 1 fuses before metatarsals 2-5. More than the metatarsal fusion sequence, however, the principal evidence of the youthful age of OH 8 lies in the morphology of metatarsals 1, 2, and 3. Because both OH 8 and OH 7 come from the same stratum at the FLK NN type site, the most parsimonious explanation of the OH 8 and OH 7 data is that this material belonged to the same individual, as originally proposed by Louis Leakey. The proposition that OH 8 belonged to an adult is unsupported by morphology, including radiographic evidence, and the fusion sequences in human and chimpanzee skeletal material reported here and in the literature.     

A chimpanzee-passaged human immunodeficiency virus isolate is cytopathic for chimpanzee cells but does not induce disease.

The human immunodeficiency virus type 1 (HIV-1) readily infects both humans and chimpanzees, but the pathologic outcomes of infection in these two species differ greatly. In attempts to identify virus-cell interactions that might account for this differential pathogenicity, chimpanzee peripheral blood lymphocytes and bone marrow macrophages were assessed in vitro for their ability to support the replication of several HIV-1 isolates. Although the IIIb, RF, and MN isolates did not readily infect chimpanzee peripheral blood lymphocytes, an isolate of HIV-1 passaged in vivo in chimpanzees not only replicated well in both chimpanzee peripheral blood lymphocytes and bone marrow macrophages but also was cytopathic for chimpanzee CD4+ lymphocytes. Because no evidence of HIV-induced disease has been observed in chimpanzees infected with this isolate, in vitro replication to high titers with concomitant loss of CD4+ cells is not, in this instance, a correlate of pathogenicity. These observations, therefore, indicate that caution must be used when making extrapolations from in vitro data to in vivo pathogenesis.     

A longitudinal study on hand and wrist skeletal maturation in chimpanzees ( Pan troglodytes), with emphasis on growth in linear dimensions

Skeletal maturation in the chimpanzee hand and wrist (the RUS system; radius, ulna, and short bones) was studied both longitudinally and cross-sectionally. Maturity states were evaluated in each of the 13 bones of the RUS system based on the TW2 method (Tanner and Whitehouse method), and the RUS score was calculated by the summation of scores for these bones. Individual variation was examined by means of residual curves and pseudo-velocity curves of RUS score and anterior trunk length (ATL). Norms of the age change pattern in RUS skeletal maturation and the growth of ATL were determined for each sex, and the relationships among ATL growth and skeletal and reproductive maturation were examined. We found a fairly good relationship between ATL growth and RUS skeletal maturation. Comparison of growth and development between humans and chimpanzees showed that growth characteristics are coupled with each other at puberty in male chimpanzees and in both sexes of humans. Although nutritional condition influenced ATL growth in infancy, it had no effect on the RUS maturational process. Social relationships appeared to influence both ATL growth and RUS maturation. Analyses on relationships between RUS skeletal maturation, ATL growth, and reproductive maturation, showed that RUS skeletal maturation is a good indicator of "physiological age".     

Dehydroepiandrosterone-sulfate (DHEA-S), sex,and age in zoo-housed western lowland gorillas (<Emphasis Type="Italic">Gorilla gorilla gorilla</Emphasis>)

Among humans, dehydroepiandrosterone-sulfate (DHEA-S) declines with age and is hypothesized to be involved in somatic maintenance and healthy aging. Men have significantly higher DHEA-S than women, contradicting longer lifespans in the latter. Declines of DHEA-S with age also are observed in chimpanzees. In both chimpanzees and bonobos, males and females show no differences in DHEA-S production. Based on human and chimpanzee data, gorillas were predicted to show declining DHEA-S with age. Similar to chimpanzees and bonobos, it also was predicted DHEA-S would not be significantly different between males and females. DHEA-S was assayed from serum banked during physical examinations of gorillas housed at three North American zoos (n = 63). Gorillas ranged from 6 to 52 years of age. Differences between males and females were examined using t tests. Linear regression was used to determine the relationship of DHEA-S with age. There was no significant difference in DHEA-S between males and females. Additionally, there was no significant relationship between DHEA-S and age. As predicted, there were no sex-based differences in DHEA-S in gorillas, which is similar to chimpanzees and bonobos but different from modern humans. Unlike chimpanzees and humans, there was no significant relationship between DHEA-S and age in gorillas. The absence of a relationship between age and DHEA-S may be due to the lack of gorillas under age 6 years in this sample as declines in chimpanzees occur prior to age 5 years, more rapid growth and development among gorillas compared with other African hominoids, or a unique pattern of DHEA-S production.     

Evolutionary insights into primate skeletal gene regulation using a comparative cell culture model

The evolution of complex skeletal traits in primates was likely influenced by both genetic and environmental factors. Because skeletal tissues are notoriously challenging to study using functional genomic approaches, they remain poorly characterized even in humans, let alone across multiple species. The challenges involved in obtaining functional genomic data from the skeleton, combined with the difficulty of obtaining such tissues from nonhuman apes, motivated us to consider an alternative in vitro system with which to comparatively study gene regulation in skeletal cell types. Specifically, we differentiated six human (Homo sapiens) and six chimpanzee (Pan troglodytes) induced pluripotent stem cell lines (iPSCs) into mesenchymal stem cells (MSCs) and subsequently into osteogenic cells (bone cells). We validated differentiation using standard methods and collected single-cell RNA sequencing data from over 100,000 cells across multiple samples and replicates at each stage of differentiation. While most genes that we examined display conserved patterns of expression across species, hundreds of genes are differentially expressed (DE) between humans and chimpanzees within and across stages of osteogenic differentiation. Some of these interspecific DE genes show functional enrichments relevant in skeletal tissue trait development. Moreover, topic modeling indicates that interspecific gene programs become more pronounced as cells mature. Overall, we propose that this in vitro model can be used to identify interspecific regulatory differences that may have contributed to skeletal trait differences between species.     

Heterochrony and sexual dimorphism in the skull of the Liberian chimpanzee (Pan troglodytes verus)

Allometric methods and theory derived from principles of relative growth provide new and powerful approaches to an understanding of the nature and development of sexual dimorphism among living primates. The Frankfurt collection of Liberian chimpanzee skulls and mandibles provides a large skeletal sample from a single natural population of wild shot animals, including individuals of all ages and both sexes, and allows investigation of allometric and heterochronic patterns of sexual dimorphism. Univariate, bivariate, and multivariate analyses are utilized in this study in order to ascertain the ontogenetic nature of male-female differences in the skull of the Liberian chimpanzee. The results of univariate and multivariate analyses indicate that, while overall levels of sexual dimorphism in the chimpanzee skull are small, the greatest differences are in dimensions of the viscerocranium, while neurocranial dimensions and orbital size tend to be less dimorphic. Bivariate regressions of 21 cranial variables against basicranial length document positive allometry in many facial and mandibular dimensions, and isometry or negative allometry for most neurocranial dimensions. The data confirm previous work in chimpanzees and other anthropoid primates suggesting that males and females are “ontogenetically scaled” in most cranial traits. That is, males and females share the same cranial growth trajectories, although ending up at different points. Both rate and time hypermorphosis are suggested as underlying causes of ontogenetic scaling in the Liberian chimpanzee.     

Apparent age-related bone loss among adult female Gombe chimpanzees

Apparent age-related bone loss among adult females was observed in a skeletal sample derived from the free-ranging Gombe chimpanzee population of Tanzania. Photon absorptiometric and computed tomographic bone scans indicated that, as in humans, bone was lost from the endosteal surface, but, in contrast to humans, more bone was lost from cortical sites than from cancellous sites. The etiology of this bone loss may be related to a number of factors, including hormonal changes, nutritional inadequacy, and decreased physical activity late in life coupled with the demands of pregnancy and lactation.