Urinary estrogen excretion during pregnancy in the gorilla (Gorilla gorilla), orangutan (Pongo pygmaeus) and the human (Homo sapiens)

Urinary estrogen components were separated, identified and quantified throughout the pregnancy of the gorilla (Gorilla gorilla) and orangutan (Pongo pygmaeus) and compared to estrogen levels in normal human pregnancies. Fetal and neonatal adrenals from each species were also compared in terms of weight and relative amounts of fetal zone. The results demonstrate that gorillas and chimpanzees excrete 4- to 5-fold less estrogen during pregnancy than the human and orangutan which are similar to each other. The lower estrogen excretion appears to be related to a smaller fetal adrenal in both the gorilla and chimpanzee which reveal both a reduced adrenal weight and increased definitive to fetal zone ratio when compared to either the human or orangutan.     

Hand preference in a captive island group of chimpanzees (Pan troglodytes)

Morphological cerebral asymmetries in chimpanzee brains, similar to those found in humans, in whom they are associated with speech and handedness, suggest the possibility of functional lateralization in the chimpanzee. This possibility was investigated by examining hand preferences in an island group of five chimpanzees on a series of unimanual and bimanual tasks that are diagnostic of human hand and cerebral dominance. Each subject was tested in a double compartment cage on three unimanual nonsequential, three unimanual sequential, and three bimanual coordination tasks. One of the three unimanual sequential tasks was a bar-press task that is analogous to the commonly used human finger-tapping task. For the unimanual tasks, exclusive of the bar-press, the chimpanzees showed a highly individualistic pattern of hand preference that did not change as a function of task complexity. On the bar-press task, four of five subjects produced higher rates with one hand compared to the other; however, relative hand performance on this task was unrelated to hand preference on the other unimanual tasks. For the group of subjects, performance rates did not differ between the left and right hands; however, a practice effect was observed for the right hand in all subjects. The bimanual tasks also revealed a complex pattern of individual handedness, with no trends apparent for the group as a whole. Consistent with previous findings, the results from these tests on this group of five chimpanzees suggest that cerebral morphological asymmetries in the chimpanzee are not associated with motor dominance as reflected in handedness.     

A comparison of the small ribosomal RNA genes from the mitochondrial DNA of the great apes and humans: sequence, structure, evolution, and phylogenetic implications

Restriction endonuclease fragments produced by EcoRI/AvaI or KpnI digestion and containing the small (12S) ribosomal RNA (rRNA) genes from the mitochondrial DNAs (mtDNAs) of the common chimpanzee, pygmy chimpanzee, gorilla, and orangutan were inserted into the plasmids pBR322 or pADD1. After species verification the inserted fragments were digested with SauIIIA, subcloned into M13mp7 vectors, and sequenced. The small rRNA gene sequences were compared with each other and with the published human sequence (Anderson et al. 1981). Substitutions were detected at 118 of the 955 nucleotide positions compared. Pairwise, the sequence differences ranged from 1% (between the chimpanzee species) to 9% (comparisons involving the orangutan); the proportion that were transitions ranged from 87% to 100%. Deletions and/or additions were noted at seven locations. With respect to evolutionary sequence lability, kinetic analysis indicated the presence of at least two classes of nucleotide positions; the more labile class occurs in sequences thought to form self-complementary duplexes (stems) in the mature rRNA. The high frequency of compensating substitutions, which maintain base-pairing within these sequences, corroborates their inferred structure. Phylogenetic inferences drawn from the sequence comparisons support the notion of an approximately equidistant relationship among chimpanzees, gorilla, and man, with the orangutan much less closely related. However, inference from a shared deletion suggests that the gorilla and the chimpanzees may be more closely related to one another than they are to man.     

Evolution of glycophorin A in the hominoid primates studied with monoclonal antibodies, and description of a sialoglycoprotein analogous to human glycophorin B in chimpanzee

Comparison of human and primate erythrocyte membrane sialoglycoproteins showed that common chimpanzee, dwarf chimpanzee, gorilla, orangutan, and gibbon have major periodic acid Schiff-positive proteins resembling human glycophorin A (GPA) monomer and dimer in electrophoretic mobility on sodium dodecyl sulfate-polyacrylamide gels. Immunoperoxidase staining of Western blots with monoclonal antibodies to human GPA showed that these primate bands express some GPA antigenic determinants. A new sialoglycoprotein analogous to human glycophorin B (GPB) was detected in common chimpanzee. Although human MN blood group phenotype results from an amino acid polymorphism of GPA, Western blots showed that in chimpanzee sialoglycoprotein (GPAch) always expresses the M blood group, whereas chimpanzee sialoglycoprotein (GPBch) expresses either the N blood group or a null phenotype. This result explains the detection of M and MN, but not of N, blood group phenotypes in chimpanzee. GPBch has higher apparent m.w. than human GPB, is present in the erythrocyte membrane in greater quantity than human GPB, and contains trypsin cleavage site(s) and the 10F7 determinant (both found on human GPA but not GPB). Expression of human GPA antigenic determinants was consistent with the phylogeny of the hominoid primates; common and dwarf chimpanzee expressed most of the determinants tested, gorilla and orangutan an intermediate number, and gibbon and siamang the least. Of the GPA antigenic determinants examined, the MN blood group determinants were most consistently expressed during evolution of the hominoid primates. The results suggested that variability in expression of GPA antigenic determinants between species was due to both differences in amino acid sequence and glycosylation.     

Visual discrimination of primate species based on faces in chimpanzees

Many primate studies have investigated discrimination of individual faces within the same species. However, few studies have looked at discrimination between primate species faces at the categorical level. This study systematically examined the factors important for visual discrimination between primate species faces in chimpanzees, including: colour, orientation, familiarity, and perceptual similarity. Five adult female chimpanzees were tested on their ability to discriminate identical and categorical (non-identical) images of different primate species faces in a series of touchscreen matching-to-sample experiments. Discrimination performance for chimpanzee, gorilla, and orangutan faces was better in colour than in greyscale. An inversion effect was also found, with higher accuracy for upright than inverted faces. Discrimination performance for unfamiliar (baboon and capuchin monkey) and highly familiar (chimpanzee and human) but perceptually different species was equally high. After excluding effects of colour and familiarity, difficulty in discriminating between different species faces can be best explained by their perceptual similarity to each other. Categorical discrimination performance for unfamiliar, perceptually similar faces (gorilla and orangutan) was significantly worse than unfamiliar, perceptually different faces (baboon and capuchin monkey). Moreover, multidimensional scaling analysis of the image similarity data based on local feature matching revealed greater similarity between chimpanzee, gorilla and orangutan faces than between human, baboon and capuchin monkey faces. We conclude our chimpanzees appear to perceive similarity in primate faces in a similar way to humans. Information about perceptual similarity is likely prioritized over the potential influence of previous experience or a conceptual representation of species for categorical discrimination between species faces.     

A comparative study on testicular microstructure and relative sperm production in gorillas, chimpanzees, and orangutans

We performed histological analyses for comparing testicular microstructure between the gorilla, chimpanzee, and orangutan. Testicular samples were obtained by autopsy or biopsy from 10 gorillas, 11 chimpanzees, and 7 orangutans from several zoos and institutes. The seminiferous epithelia were thick in the chimpanzee and orangutan but thin in the gorilla. Leydig cells in the interstitial tissue were abundant in the gorilla. The acrosomic system was extremely well developed in the orangutans. Our study reveals that the cycle of seminiferous epithelium in orangutan testis can be divided into ten stages, whereas that in human, chimpanzee, and gorilla testes can be divided into only six stages. Phylogenetic analyses of the number of divisions may indicate that the seminiferous epithelium of our common ancestor has changed since the orangutan diverged from it. Furthermore, we performed comparative analyses of testicular microstructure to estimate relative sperm production among these three animals, and proposed a new indicator (namely the spermatogenic index, SI) closely related to sperm production. The SI indicated that a chimpanzee usually produces about 223 times more sperm than a gorilla and about 14 times more than an orangutan. Our data demonstrate the significance of the SI for estimating sperm production, thus aiding our understanding of the reproductive strategy as well as testis weight and relative testis size in investigated primates.     

Antigens and DNA of a chimpanzee agent related to Epstein-Barr virus.

Biological and biochemical studies of the herpesvirus of chimpanzees previously demonstrated to be antigenically related to human Epstein-Barr virus (EBV) indicated that the agent is similar to EBV in that: (i) leukocyte culture of chimpanzees whose sera contained antibody against EBV capsid antigen could yield long-term lymphoblastoid cell lines (Ch-LCL) with B-cell characteristics; (ii) the DNA of Ch-LCL contained sequences homologous to approximately 35 to 45% of human EBV; (iii) Ch-LCL contained an intranuclear antigen, Ch-NA, that could be identified with some chimpanzee or orangutan serum in anticomplimentary immunofluorescence assays; and (iv) treatment of Ch-LCL with iododeoxyuridine resulted in expression of new antigenic activity that reacted with EA+ but not EA- human sera. Two lines of evidence indicate that the chimpanzee agent, although related to human EBV, is a distinct agent: (i) Ch-NA was antigenically distinct from EBV-rebv infection although it cross-reacts of a limited extent with a minor component of EBNA; and (ii) Ch-LCL are missing 55 to 65% of the DNA sequences of human EBV.     

Nutritive and non-nutritive sucking in preterm infants

Nutritive and non-nutritive sucking was studied in 9 preterm infants with postmenstrual ages ranging from 28 to 33 weeks and postnatal ages ranging from 0 to 8 weeks. During nutritive sucking, sucking bursts were longer than sucking pauses. During non-nutritive sucking the opposite was seen. The sucking rate was lower during nutritive sucking. During nutritive sucking the respiratory rate was higher during the pauses than during the bursts. During non-nutritive sucking the respiratory rate was higher during sucking. It is concluded that non-nutritive sucking cannot serve as a model for studying feeding mechanisms in the preterm infant.     

Analysis of chimpanzee history based on genome sequence alignments

Population geneticists often study small numbers of carefully chosen loci, but it has become possible to obtain orders of magnitude for more data from overlaps of genome sequences. Here, we generate tens of millions of base pairs of multiple sequence alignments from combinations of three western chimpanzees, three central chimpanzees, an eastern chimpanzee, a bonobo, a human, an orangutan, and a macaque. Analysis provides a more precise understanding of demographic history than was previously available. We show that bonobos and common chimpanzees were separated ~1,290,000 years ago, western and other common chimpanzees ~510,000 years ago, and eastern and central chimpanzees at least 50,000 years ago. We infer that the central chimpanzee population size increased by at least a factor of 4 since its separation from western chimpanzees, while the western chimpanzee effective population size decreased. Surprisingly, in about one percent of the genome, the genetic relationships between humans, chimpanzees, and bonobos appear to be different from the species relationships. We used PCR-based resequencing to confirm 11 regions where chimpanzees and bonobos are not most closely related. Study of such loci should provide information about the period of time 5–7 million years ago when the ancestors of humans separated from those of the chimpanzees.     

Stresses exerted in the hindlimb muscles of common chimpanzees (Pan troglodytes) during bipedal locomotion

Recent studies have indicated that chimpanzee bipedality is mechanically inefficient and dynamically unlike that of humans, thus undermining the chimpanzee analogy for mechanical aspects of the early evolution of hominid bipedalism. This paper continues this theme by measuring the forces and stresses engendered by the muscles during bipedal locomotion, for an untrained chimpanzee and for data from chimpanzees which have been encouraged to walk bipedally, presented in the literature. Peak stresses in the triceps surae were lower for the untrained chimpanzee than for the trained subjects because during the late stance phase, when peak ankle moments occur, the centre of pressure of the ground reaction force on the foot of the untrained chimpanzee stayed close to the ankle joint. In contrast, for the trained subjects it moved closer to the toes, as in human bipedalism. Quadriceps and hip extensor stresses are approximately 30% larger for the untrained chimpanzee than for the trained subjects, because the trained chimpanzees walked with a more erect posture. These results may reflect the way in which muscles can develop in response to training, since research on humans has shown that muscle physiological cross-sectional area increases as a result of exercise, resulting in smaller stresses for a given muscle force. During a slow walk, untrained chimpanzees were found to exert far greater muscle stresses than humans do when running at moderate speed, particularly in the muscles that extend the hip, because of the bent-hip, bent-knee posture.     

Comparative study of urinary reproductive hormones in great apes

Urinary estrone conjugates (E₁C), pregnanediol-3-glucuronide (PdG), and follicle-stimulating hormone (FSH) were determined by enzyme immunoassays (EIAs) during the normal menstrual cycle in the orangutan, gorilla, chimpanzee, and bonobo. Furthermore, the data were compared to those levels in the human and long-tailed macaque. The results showed a typical preovulatory E₁C surge and postovulatory increase in PdG in all species. The pattern of E₁C during the menstrual cycle in the great apes more closely resembled the human than do the long-tailed macaque. A major difference of E₁C pattern between these species appeared in the luteal phase. In the great apes and the human, E₁C exhibited two peaks, the first peak detected at approximately mid cycle and the second peak detected during the luteal phase. On the other hand, in the long-tailed macaque, increase of E₁C in the luteal phase was small or nonexistent. The gorilla, chimpanzee, and bonobo exhibited similar PdG trends. The orangutan excreted one tenth less PdG than these species during the luteal phase. The long-tailed macaque also excreted low levels of PdG. The patterns of FSH in orangutan, chimpanzee, bonobo and long-tailed macaque showed a marked mid-cycle rise and an early follicular phase rise, similar to those in the human. Comparing similar taxa, a large difference was found in FSH of gorilla; there were three peaks during the menstrual cycle. Thus, there is considerable species variation in the excretion of these hormones during the menstrual cycle and comparative studies could be approached with a single method. The methods and baseline data presented here provide the basis for a practical approach to evaluation and monitoring of ovarian events in the female great apes. Electronic Publication     

The mitochondrial DNA molecule of sumatran orangutan and a molecular proposal for two (Bornean and Sumatran) species of orangutan

The complete mitochondrial DNA (mtDNA) molecule of Sumatran orangutan, plus the complete mitochondrial control region of another Sumatran specimen and the control regions and five protein-coding genes of two specimens of Bornean orangutan were sequenced and compared with a previously reported complete mtDNA of Bornean orangutan. The two orangutans are presently separated at the subspecies level. Comparison with five different species pairs—namely, harbor seal/grey seal, horse/donkey, fin whale/blue whale, common chimpanzee/pygmy chimpanzee, and Homo/common chimpanzee—showed that the molecular difference between Sumatran and Bornean orangutan is much greater than that between the seals, and greater than that between the two chimpanzees, but similar to that between the horse and the donkey and the fin and blue whales. Considering their limited morphological distinction the comparison revealed unexpectedly great molecular difference between the two orangutans. The nucleotide difference between the orangutans is about 75% of that between Homo and the common chimpanzee, whereas the amino acid difference exceeds that between Homo and the common chimpanzee. On the basis of their molecular distinction we propose that the two orangutans should be recognized as different species, Pongo pygmaeus, Bornean orangutan, and P. abelii, Sumatran orangutan. Received: 15 May 1996 / Accepted: 21 June 1996     

人猿超科和旧大陆猴7种高等灵长类FKN全基因序列的测定及进化分析

测定人猿超科(人、黑猩猩、大猩猩、红毛猩猩和长臂猿)和旧大陆猴(猕猴和叶猴)7种高等灵长类FKN全基因序列, 探讨其系统进化分析。用简并引物PCR(Degenerated PCR)法分别扩增FKN的3个外显子, 其产物经琼脂糖凝胶回收、纯化后测序, 然后用BioEdit软件剪切拼接FKN基因全序列, 用DNAStar比对后比较基因和氨基酸序列同源性, Mega软件重构FKN基因进化树, 应用Datamonkey分析FKN的负选择位点。序列分析发现人猿超科较旧大陆猴FKN基因除了有散在的点突变外, 还有一明显的30 bp的核苷酸缺失突变; 人FKN基因序列与黑猩猩、大猩猩、红毛猩猩、长臂猿、猕猴和叶猴的同源性分别是99.2%、98.4%、98.1%、96.5%、95.9%和93.8%, 由此推导的氨基酸序列同源性分别是98.5%、98.0%、97.7%、94.7%、93.7%和90.5%; FKN基因进化树表明人与黑猩猩关系更近, FKN基因进化和通常认为的物种进化一致; Datamonkey分析结果显示FKN存在3个负选择位点53Q、84D、239N。成功获得人、黑猩猩、大猩猩、红毛猩猩、长臂猿、猕猴和叶猴7种高等灵长类物种FKN全基因序列, 为后续探讨FKN在高等灵长类物种进化过程中免疫学功能演变及其结构与功能的关系奠定基础。     

Serum cholinesterase activities and inhibition profiles of nonhuman primates

Serum cholinesterase activities and inhibition profiles of 169 chimpanzees, 15 gorillas, 26 orangutans, seven gibbons, and 12 rhesus monkeys were determined. Mean values of activities against benzoylcholine (μmols/min/ml) and dibucaine, fluoride, and Ro 2-0683 numbers (percentage inhibition of benzoylcholine hydrolysis) are: chimpanzee, 2.276, 80, 64, and 97; gorilla, 9.403, 82, 71, and 96; orangutan, 0.747, 94, 6, and 98; gibbon, 0.071, 89, 7, and 94; and rhesus monkey, 0.859, 95, 10, and 99, respectively. Sernylan numbers were determined of the last 100 chimpanzee serums collected and of each of the gorilla, orangutan, gibbon, and rhesus monkey serums. Mean values of Sernylan numbers are: chimpanzee, 80; gorilla, 81; orangutan, 95; gibbon, 94; and rhesus monkey, 96. The chimpanzee and the gorilla have dibucaine, fluoride, Ro 2-0683, and Sernylan numbers within the range found in men who are homozygotes for the usual cholinesterase (genotype E₁^uE₁^u). No cholinesterase variant was found in any chimpanzee or gorilla. The orangutan, gibbon, and rhesus monkey have inhibition profiles that resemble one another, with higher dibucaine and Sernylan numbers and much lower fluoride numbers than the chimpanzee or the gorilla. The results of the inhibition tests suggest that the African apes, chimpanzee and gorilla, are related more closely to man than are the Asian apes, orangutan and gibbon.     

Chimpanzee apolipoprotein H (beta2-glycoprotein I): report on the gene structure, a common polymorphism, and a high prevalence of antiphospholipid antibodies

Apolipoprotein H (apoH, protein; APOH, gene) is a 50-kDa glycoprotein that binds to negatively charged substrates, including phospholipids. ApoH is a main target antigen for the binding of antiphospholipid antibodies that are associated with thrombotic events. We have previously characterized the structural organization of the human APOH gene. Because of the significant structural homology between the human and chimpanzee genomes, we have employed oligonucleotides from the human APOH gene sequence to amplify chimpanzee DNA covering the entire transcribed region together with flanking sequence in the 5' region. As in humans, the chimpanzee APOH gene consists of eight exons and seven introns and encodes for a 326-amino-acid protein. The deduced amino acid and nucleotide sequence show 99.4% and 99.6% similarity between human and chimpanzee APOH, respectively. Using isoelectric focusing (IEF) and immunoblotting, we screened 155 chimpanzees (128 unrelated captured parents and 27 captive-born offspring) for the apoH protein polymorphism. The most common IEF pattern in chimpanzees was identical to a previously described APOH*3 allele in humans. In addition, an anodally shifted pattern was observed in chimpanzees with an allele frequency of 0.168, and the corresponding allele was designated as APOH*4. DNA sequencing of APOH*4 carriers revealed a missense mutation in exon 6 (A-->G) at codon 210, which replaces the amino acid lysine by glutamic acid. This mutation does not affect the binding of apoH to cardiolipin as revealed by cardiolipin/enzyme-linked immunosorbent assay (ELISA). We also evaluated the prevalence of anti-apoH antibodies in chimpanzee plasma by using human-apoH-based ELISA and the association of the Lys210Glu mutation with the occurrence of anti-apoH antibodies. The prevalence of anti-apoH antibodies in chimpanzees (64%) was found to be unusually high compared with that found in humans. However, the Lys210Glu mutation showed no association with the occurrence of anti-apoH antibodies. The prevalence of anti-apoH antibodies in chimpanzees may serve as a useful animal model for the human antiphospholipid syndrome, where these antibodies are associated with clinical manifestations.     

Man's place in hominoidea revealed by mitochondrial DNA genealogy

Summary Molecular biology has resurrected C. Darwin and T.H. Huxley's question about the origin of humans, but the precise branching pattern and dating remain controversial. To settle this issue, a large amount of sequence information is required. We determined mitochondrial (mt) DNA sequences for five hominoids; pygmy and common chimpanzees, gorilla, orangutan, and siamang. The common region compared with the known human sequence is 4759 by long, encompassing genes for 11 transfer RNAs and 6 proteins. Because of the high substitution rates in mammalian mtDNA and an unprecedentedly large region compared, the sequence differences clearly indicate that the closest relatives to human are chimpanzees rather than gorilla. For dating the divergences of human, chimpanzee, and gorilla, we used only unsaturated parts of sequence differences in which the mtDNA genealogy is not obscured by multiple substitutions. The result suggests that gorilla branched off 7.7 ± 0.7 million years (Myr) ago and human 4.7 ± 0.5 Myr ago; the time difference between these divergences being as long as 3 Myr.Offprint requests to: S. Horai     

Higher-primate phylogeny--why can't we decide?

At present, no definitive agreement on either the correct branching order or differential rates of evolution among the higher primates exists, despite the accumulated integration of decades of morphological, immunological, protein and nucleic acid sequence data, and numerous reasonable theoretical models for the analysis, interpretation, and understanding of those data. Of the three distinct unrooted phylogenetic trees, that joining human with chimpanzee and the gorilla with the orangutan is currently favored, but the two alternatives that group humans with either gorillas or the orangutan rather than with chimpanzees also have support. This paper is a synthetic and critical review of the methodological literature and isolates some 20 specific reasons why uncertainty in the evolutionary understanding of our closest living relatives persists. Many of the difficulties are eliminated or ameliorated by Lake's new methods of phylogenetic invariants and operator metrics. In the companion paper these new methods are used to analyze both the nuclear and mitochondrial DNA of the higher primates.      

Chimpanzee (Pan troglodytes) responses to caregiver use of chimpanzee behaviors

The relationships between captive primates and their caregivers are critical ones and can affect animal welfare. Friendly relationships can improve quality of life; adversely, agonistic relationships can decrease quality of life. Caregivers in and of themselves should not be stressful to their charges, instead the caregivers' behaviors and the nature of their interactions with captive primates is likely the basis for the stress. One method to promote positive relationships in the captive environment is for caregivers to employ species‐specific behaviors in their interactions with their charges. This study tested the effect of caregivers' use of these behaviors with chimpanzees at The Zoo Northwest Florida in Gulf Breeze. The chimpanzee participants were three males. Data collection occurred during typical interactions between the human participants and the chimpanzees. Some days the caregiver presented chimpanzee behaviors and vocalizations (CB—Chimpanzee Behavior Condition) in the data collection interactions with the chimpanzees. On other days the caregiver presented human behaviors and used speech (HB—Human Behavior Condition) in the interactions with the chimpanzees. The interactions were videotaped. Data coders recorded the behavioral contexts for each chimpanzee as they occurred on the videotape and the time that each context began. Overall they engaged in significantly more friendly behaviors such as play in CB than in HB. They were significantly less interactive in HB than CB. Caregivers should understand and employ species‐specific interactions with chimpanzees to promote friendly interactions and animal welfare. Zoo Biol 27:345–359, 2008. © 2008 Wiley‐Liss, Inc.     

Fruit availability, chimpanzee diet, and grouping patterns on Rubondo Island, Tanzania

We examined seasonal patterns of fruit availability, dietary quality, and group size in the descendants of an introduced chimpanzee population on Rubondo Island, Tanzania. The site has supported a free-ranging population without provisioning for 40 years. Our goals were to determine whether Rubondo chimpanzees experience periods of fruit shortage, and whether they respond to changes in fruit availability similarly to chimpanzees at endemic sites. We indexed the fruit availability of tree and liana species on transects stratified across three chimpanzee ranging areas. We used fecal analyses to evaluate seasonal changes in diet, and used data on party size and nesting group size to examine seasonal patterns of grouping. Tree fruit availability was positively correlated with rainfall, with a period of relative tree fruit scarcity corresponding with the long dry season. Liana fruit availability was not related to rainfall, and lianas exhibited less variable fruiting patterns across seasons. Fruits made up the majority of the chimpanzee diet, with lianas accounting for 35% of dietary fruit species. Fruits of the liana Saba comorensis were available during all months of phenological monitoring, but they were consumed more when tree fruit was scarce, suggesting that Saba comorensis fruits may be a fallback food for Rubondo chimpanzees. There were no increases in consumption of lower-quality plant parts between seasons, and there were no changes in group size between seasons. These results contrast with evidence from several endemic chimpanzee study sites, and indicate that Rubondo chimpanzees may have access to abundant and high-quality foods year round.     

Contrasting effects of natural selection on human and chimpanzee CC chemokine receptor 5

Human immunodeficiency virus type 1 (HIV-1) evolved via cross-species transmission of simian immunodeficiency virus (SIVcpz) from chimpanzees (Pan troglodytes). Chimpanzees, like humans, are susceptible to infection by HIV-1. However, unlike humans, infected chimpanzees seldom develop immunodeficiency when infected with SIVcpz or HIV-1. SIVcpz and most strains of HIV-1 require the cell-surface receptor CC chemokine receptor 5 (CCR5) to infect specific leukocyte subsets, and, subsequent to infection, the level of CCR5 expression influences the amount of HIV-1 entry and the rate of HIV-1 replication. Evidence that variants in the 5' cis-regulatory region of CCR5 (5'CCR5) affect disease progression in humans suggests that variation in CCR5 might also influence the response of chimpanzees to HIV-1/SIVcpz. To determine whether patterns of genetic variation at 5'CCR5 in chimpanzees are similar to those in humans, we analyzed patterns of DNA sequence variation in 37 wild-born chimpanzees (26 P. t. verus, 9 P. t. troglodytes, and 2 P. t. schweinfurthii), along with previously published 5'CCR5 data from 112 humans and 50 noncoding regions in the human and chimpanzee genomes. These analyses revealed that patterns of variation in 5'CCR5 differ dramatically between chimpanzees and humans. In chimpanzees, 5'CCR5 was less diverse than 80% of noncoding regions and was characterized by an excess of rare variants. In humans, 5'CCR5 was more diverse than 90% of noncoding regions and had an excess of common variants. Under a wide range of demographic histories, these patterns suggest that, whereas human 5'CCR5 has been subject to balancing selection, chimpanzee 5'CCR5 has been influenced by a selective sweep. This result suggests that chimpanzee 5'CCR5 might harbor or be linked to functional variants that influence chimpanzee resistance to disease caused by SIVcpz/HIV-1.