The evolutionary relationships of man and orang-utans

Systematics of Miocene apes: State of the art of a neverending controversy

Hominoids diverged from cercopithecoids during the Oligocene in Afro-Arabia, initially radiating in that continent and subsequently dispersing into Eurasia. From the Late Miocene onward, the geographic range of hominoids progressively shrank, except for hominins, which dispersed out of Africa during the Pleistocene. Although the overall picture of hominoid evolution is clear based on available fossil evidence, many uncertainties persist regarding the phylogeny and paleobiogeography of Miocene apes (nonhominin hominoids), owing to their sparse record, pervasive homoplasy, and the decimated current diversity of this group. We review Miocene ape systematics and evolution by focusing on the most parsimonious cladograms published during the last decade. First, we provide a historical account of the progress made in Miocene ape phylogeny and paleobiogeography, report an updated classification of Miocene apes, and provide a list of Miocene ape species-locality occurrences together with an analysis of their paleobiodiversity dynamics. Second, we discuss various critical issues of Miocene ape phylogeny and paleobiogeography (hylobatid and crown hominid origins, plus the relationships of Oreopithecus) in the light of the highly divergent results obtained from cladistic analyses of craniodental and postcranial characters separately. We conclude that cladistic efforts to disentangle Miocene ape phylogeny are potentially biased by a long-branch attraction problem caused by the numerous postcranial similarities shared between hylobatids and hominids-despite the increasingly held view that they are likely homoplastic to a large extent, as illustrated by Sivapithecus and Pierolapithecus-and further aggravated by abundant missing data owing to incomplete preservation. Finally, we argue that-besides the recovery of additional fossils, the retrieval of paleoproteomic data, and a better integration between cladistics and geometric morphometrics-Miocene ape phylogenetics should take advantage of total-evidence (tip-dating) Bayesian methods of phylogenetic inference combining morphologic, molecular, and chronostratigraphic data. This would hopefully help ascertain whether hylobatid divergence was more basal than currently supported.

DNA DIVERGENCE AMONG HOMINOIDS

We have determined the degree of single-copy DNA divergence among the extant members of the Hominoidea employing the technique of DNA-DNA hybridization. The species studied include humans, two species of chimpanzees, gorillas, two subspecies of orangutans, and two species of gibbons; as an outgroup we have used a member of the Old World monkeys (Cercopithecidae), the baboon. Our methods are different from those previously used and allow us to control for two factors other than base-pair mismatch that can affect the thermal stability of DNA duplexes: the base composition and duplex length. In addition, we have studied more than one individual for most species and thus are able to assess the effect of intraspecific variation on phylogenetic conclusions. The results indicate that the closest extant relatives of humans are the chimpanzees. Gorillas are the next closest, followed by orangutans and gibbons. This result is strongly supported statistically, as there is virtually no overlap in measurements between different taxa. Our conclusions are in agreement with a growing amount of molecular evidence supporting this pattern of relatedness. The data behave as a reasonably good molecular clock, and we do not see an indication of slowdown in molecular evolution in the clade containing humans and African apes, contrary to what has been documented for protein-coding regions. Because of the clocklike nature of the results, we have estimated that the divergence of humans and chimpanzees occurred about 6-8 million years ago. Results from orangutans indicate that the Borneo and Sumatra populations are genetically distinct, about as different as the named species of chimpanzees.

The Genetic Equidistance Result of Molecular Evolution is Independent of Mutation Rates

The well-established genetic equidistance result shows that sister species are approximately equidistant to a simpler outgroup as measured by DNA or protein dissimilarity. The equidistance result is the most direct evidence, and remains the only evidence, for the constant mutation rate interpretation of this result, known as the molecular clock. However, data independent of the equidistance result have steadily accumulated in recent years that often violate a constant mutation rate. Many have automatically inferred non-equidistance whenever a non-constant mutation rate was observed, based on the unproven assumption that the equidistance result is an outcome of constant mutation rate. Here it is shown that the equidistance result remains valid even when different species can be independently shown to have different mutation rates. A random sampling of 50 proteins shows that nearly all proteins display the equidistance result despite the fact that many proteins have non-constant mutation rates. Therefore, the genetic equidistance result does not necessarily mean a constant mutation rate. Observations of different mutation rates do not invalidate the genetic equidistance result. New ideas are needed to explain the genetic equidistance result that must grant different mutation rates to different species and must be independently testable.

Reconstructing phylogenies and phenotypes: a molecular view of human evolution

This review broadly summarizes how molecular biology has contributed to our understanding of human evolution. Molecular anthropology began in the 1960s with immunological comparisons indicating that African apes and humans were closely related and, indeed, shared a common ancestor as recently as 5 million years ago. Although initially dismissed, this finding has proven robust and numerous lines of molecular evidence now firmly place the human-ape divergence at 4-8 Ma. Resolving the trichotomy among humans, chimpanzees and gorillas took a few more decades. Despite the readily apparent physical similarities shared by African apes to the exclusion of modern humans (body hair, knuckle-walking, thin tooth enamel), the molecular support for a human-chimpanzee clade is now overwhelming. More recently, whole genome sequencing and gene mapping have shifted the focus of molecular anthropology from phylogenetic analyses to phenotypic reconstruction and functional genomics. We are starting to identify the genetic basis of the morphological, physiological and behavioural traits that distinguish modern humans from apes and apes from other primates. Most notably, recent comparative genomic analyses strongly indicate that the marked differences between modern humans and chimpanzees are likely due more to changes in gene regulation than to modifications of the genes themselves, an idea first proposed over 30 years ago. Almost weekly, press releases describe newly identified genes and regulatory elements that seem to have undergone strong positive selection along the human lineage. Loci involved in speech (e.g. FOXP2), brain development (e.g. ASPM), and skull musculature (e.g. MYH16) have been of particular interest, but some surprising candidate loci (e.g. those involved in auditory capabilities) have emerged as well. Exciting new research avenues, such as the Neanderthal Genome Project, promise that molecular analyses will continue to provide novel insights about our evolution. Ultimately, however, these molecular findings can only be understood in light of data from field sites, morphology labs, and museum collections. Indeed, molecular anthropology depends on these sources for calibrating molecular clocks and placing genetic data within the context of key morphological and ecological transitions in human evolution.

Mona Lisa smile: the morphological enigma of human and great ape evolution

The science of human evolution is confronted with the popular chimpanzee theory and the earlier but largely ignored orangutan theory. The quality and scope of published documentation and verification of morphological features suggests there is very little in morphology to support a unique common ancestor for humans and chimpanzees. A close relationship between humans and African apes is currently supported by only eight unproblematic characters. The orangutan relationship is supported by about 28 well-supported characters, and it is also corroborated by the presence of orangutan-related features in early hominids. The uniquely shared morphology of humans and orangutans raises doubts about the almost universal belief that DNA sequence similarities necessarily demonstrate a closer evolutionary relationship between humans and chimpanzees. A new evolutionary reconstruction is proposed for the soft tissue anatomy, physiology, and behavioral biology of the first hominids that includes concealed ovulation, male beard and mustache, prolonged mating, extended pair-bonding, "house" construction, mechanical "genius," and artistic expression.

Lineage-specific expansions of retroviral insertions within the genomes of African great apes but not humans and orangutans

Retroviral infections of the germline have the potential to episodically alter gene function and genome structure during the course of evolution. Horizontal transmissions between species have been proposed, but little evidence exists for such events in the human/great ape lineage of evolution. Based on analysis of finished BAC chimpanzee genome sequence, we characterize a retroviral element (Pan troglodytes endogenous retrovirus 1 [PTERV1]) that has become integrated in the germline of African great ape and Old World monkey species but is absent from humans and Asian ape genomes. We unambiguously map 287 retroviral integration sites and determine that approximately 95.8% of the insertions occur at non-orthologous regions between closely related species. Phylogenetic analysis of the endogenous retrovirus reveals that the gorilla and chimpanzee elements share a monophyletic origin with a subset of the Old World monkey retroviral elements, but that the average sequence divergence exceeds neutral expectation for a strictly nuclear inherited DNA molecule. Within the chimpanzee, there is a significant integration bias against genes, with only 14 of these insertions mapping within intronic regions. Six out of ten of these genes, for which there are expression data, show significant differences in transcript expression between human and chimpanzee. Our data are consistent with a retroviral infection that bombarded the genomes of chimpanzees and gorillas independently and concurrently, 3–4 million years ago. We speculate on the potential impact of such recent events on the evolution of humans and great apes.

Comparison of human and other primate genomes provides evidence for a retroviral infection that bombarded the genomes of chimpanzees and gorillas 3-4 million years ago

The phylogenetic position of Morotopithecus

The phylogenetic relationship of the Ugandan Miocene hominoid Morotopithecus bishopi to fossil and living hominoids remains to be determined. In a cladistic approach to this question, we used three published Miocene character sets as the basis of a phylogenetic analysis: J. Hum. Evol. 29 (1995) 101; Function, Phylogeny, and Fossils: Miocene Hominoid Evolution and Adaptations, 1997, 389. Because these datasets often describe the same anatomy using different characters and states, three different datasets were created to reflect these alternatives. In addition, new postcranial characters describable in Morotopithecus were added to each of the above datasets and a fourth dataset was created using only postcranial characters. The most parsimonious tree(s) recovered in all analyses consistently placed Morotopithecus as a sister taxon to the extant great apes, with Hylobates sister to this clade. Morotopithecus was also consistently more derived than Proconsul, Afropithecus, and Kenyapithecus (as defined prior to the description of Equatorius), but less derived than Oreopithecus, Sivapithecus (only craniodentally) and Dryopithecus. These results imply that Morotopithecus is more derived than Hylobates. However, gibbons are believed to have branched off by at least 18 Ma while Morotopithecus is dated at >20.6 Ma. Possible explanations include: (1) the dating of the Morotopithecus material is too old; (2) the Hylobates divergence time has been underestimated; (3) the great ape condition, and not that of Hylobates, is primitive for hominoids; (4) the similarities of Morotopithecus and great apes are homoplasies. Given current evidence, the first possibility is unlikely, but it is not possible to choose definitively between the latter three possibilities. This conclusion is supported by the fact that despite the consistencies of the analyses, the addition of Morotopithecus and the use of different characters had a large effect on the placement of other Miocene taxa. This raises questions as to the robustness of the connections between Miocene taxa and extant hominoids since different results can be achieved by changing either a few characters, or by adding a single taxon. Many of the characters used to estimate phylogeny may need to be reassessed before a reliable assessment of the phylogenetic position of Morotopithecus can be achieved.

Soft-tissue anatomy of the extant hominoids: a review and phylogenetic analysis

This paper reports the results of a literature search for information about the soft-tissue anatomy of the extant non-human hominoid genera, Pan, Gorilla, Pongo and Hylobates, together with the results of a phylogenetic analysis of these data plus comparable data for Homo. Information on the four extant non-human hominoid genera was located for 240 out of the 1783 soft-tissue structures listed in the Nomina Anatomica. Numerically these data are biased so that information about some systems (e.g. muscles) and some regions (e.g. the forelimb) are over-represented, whereas other systems and regions (e.g. the veins and the lymphatics of the vascular system, the head region) are either under-represented or not represented at all. Screening to ensure that the data were suitable for use in a phylogenetic analysis reduced the number of eligible soft-tissue structures to 171. These data, together with comparable data for modern humans, were converted into discontinuous character states suitable for phylogenetic analysis and then used to construct a taxon-by-character matrix. This matrix was used in two tests of the hypothesis that soft-tissue characters can be relied upon to reconstruct hominoid phylogenetic relationships. In the first, parsimony analysis was used to identify cladograms requiring the smallest number of character state changes. In the second, the phylogenetic bootstrap was used to determine the confidence intervals of the most parsimonious clades. The parsimony analysis yielded a single most parsimonious cladogram that matched the molecular cladogram. Similarly the bootstrap analysis yielded clades that were compatible with the molecular cladogram; a (Homo, Pan) clade was supported by 95% of the replicates, and a (Gorilla, Pan, Homo) clade by 96%. These are the first hominoid morphological data to provide statistically significant support for the clades favoured by the molecular evidence.

Soft-tissue characters in higher primate phylogenetics

Recent research has cast doubt on the reliability of bones and teeth for reconstructing phylogenetic relationships among higher primate species and genera. Herein, we investigate whether this problem is confined to hard tissues by examining the utility of higher primate soft-tissue characters for reconstructing phylogenetic relationships at low taxonomic levels. We use cladistic methods to analyze 197 soft-tissue characters for the extant hominoids and then compare the resulting phylogenetic hypotheses with the group's consensus molecular phylogeny, which is widely considered to be accurate. We show that the soft-tissue characters yield robust phylogenetic hypotheses that are compatible with the molecular phylogeny. Given the strength of the evidence for molecular phylogeny, these results indicate that, unlike craniodental hard-tissue characters, soft tissues are reliable for reconstructing phylogenetic relationships among higher primate species and genera. Thus, in higher primates at least, some types of morphological data are more useful than others for phylogeny reconstruction.

Subnasoalveolar anatomy and hominoid phylogeny: evidence from comparative ontogeny

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

Molecular evidence on primate phylogeny from DNA sequences

Evidence from DNA sequences on the phylogenetic systematics of primates is congruent with the evidence from morphology in grouping Cercopithecoidea (Old World monkeys) and Hominoidea (apes and humans) into Catarrhini, Catarrhini and Platyrrhini (ceboids or New World monkeys) into Anthropoidea, Lemuriformes and Lorisiformes into Strepsirhini, and Anthropoidea, Tarsioidea, and Strepsirhini into Primates. With regard to the problematic relationships of Tarsioidea, DNA sequences group it with Anthropoidea into Haplorhini. In addition, the DNA evidence favors retaining Cheirogaleidae within Lemuriformes in contrast to some morphological studies that favor placing Cheirogaleids in Lorisiformes. While parsimony analysis of the present DNA sequence data provides only modest support for Haplorhini as a monophyletic taxon, it provides very strong support for Hominoidea, Catarrhini, Anthropoidea, and Strepsirhini as monophyletic taxa. The parsimony DNA evidence also rejects the hypothesis that megabats are the sister group of either Primates or Dermoptera (flying lemur) or a Primate-Dermoptera clade and instead strongly supports the monophyly of Chiroptera, with megabats grouping with microbats at considerable distance from Primates. In contrast to the confused morphological picture of sister group relationships within Hominoidea, orthologous noncoding DNA sequences (spanning alignments involving as many as 20,000 base positions) now provide by the parsimony criterion highly significant evidence for the sister group relationships defined by a cladistic classification that groups the lineages to all extant hominoids into family Hominidae, divides this ape family into subfamilies Hylobatinae (gibbons) and Homininae, divides Homininae into tribes Pongini (orangutans) and Hominini, and divides Hominini into subtribes Gorillina (gorillas) and Hominina (humans and chimpanzees). A likelihood analysis of the largest body of these noncoding orthologues and counts of putative synapomorphies using the full range of sequence data from mitochondrial and nuclear genomes also find that humans and chimpanzees share the longest common ancestry.

Enamel thickness of human maxillary molars reconsidered

Forty-four modern human maxillary molars (M1 = 21, M2 = 12, and M3 = 11) were sectioned through the mesial cusps in a plane perpendicular to the cervical margin of the crown. Eight measurements of enamel thickness as well as bucco-lingual (BL) and mesio-distal (MD) diameters were recorded for each tooth in order to investigate differences in these dimensions between tooth categories. Uni- and multi-variate analyses revealed first maxillary molars to have generally thinner enamel than second or third upper molars, especially with regard to the occlusal basin. Furthermore, the decrease of MD diameters from anterior to posterior is greater than that of BL diameters. Principal Component Analysis using enamel thickness measurements resulted in complete separation of first molars, while second and third maxillary molars showed a certain amount of overlap. This finding casts doubt on using an overall measure of "molar enamel thickness" derived from mixed samples of molars for taxonomic purposes. There appears to be a relationship between bite force and enamel thickness such that posterior molars, where masticatory forces are stronger, have thicker enamel than anterior teeth. It is suggested that the gradient of enamel thickness between (and within) teeth in extant and extinct species may thus provide further information about relative wear resistance as well as the biomechanical constraints of the orofacial skeleton.

Duplication of the CD8 beta-chain gene as a marker of the man-gorilla-chimpanzee clade

In earlier studies we have found that the gene encoding the CD8 beta chain is duplicated in man. We demonstrate here that the duplicated genes are both located on chromosome 2. We have also studied the moment of the duplication event relative to the evolution of higher primates by using genomic DNA of a panel of primates. Our data strongly suggest that duplication occurred after the orangutan lineage had split and before the chimpanzee, gorilla, and man clade diverged, some 8-9.5 million years ago. This result makes the CD8 beta-chain gene duplication a convenient marker for the study of the evolution of higher primates.

Evolution and environment in the Hominoidea

Between 10 and 20 million years ago, a variety of hominoid primates lived in Africa, Europe and Asia. The question of which of these, if any, lie closest to the ancestries of humans and modern apes remains a lively source of debate. Recent fossil discoveries, though, shed light on the environments in which the various groups of hominoid emerged and, it is hoped, on their evolution. But the lack of a hominid fossil record before about 5 million years ago--and any fossil record for the African apes--is still a frustrating barrier.

A nonracial craniofacial perspective on human variation: A(ustralia) to Z(uni)

Dental and craniofacial measurements were collected for 57 samples from Asia, the Pacific, the aboriginal western hemisphere, and Europe. The craniofacial dimensions include many that are not obviously under the control of specific selective forces. Similar configurations for these in different samples should yield indications of recency of common ancestry according to the logic expressed by Darwin and evident in the relationships indicated by nuclear DNA comparisons. Dental dimensions, however, vary according to the length of time that different intensities in selective forces have been in operation. The craniofacial measurements were transformed into C scores and used to generate Euclidean distance dendrograms. When all the material was used to generate a single dendrogram, the European and Amerindian samples sorted into two regionally identifiable clusters, and the Asian and Pacific material sorted into the three clusters identified in separate previous studies: a Mainland Asian cluster, a Jomon-Pacific cluster and an Australo-Melanesian cluster. Since these clusters are based on variation in traits that are basically nonadaptive in nature, no hierarchical ranking is possible. The clusters simply reflect degree of relationship. This technique holds forth the promise of producing a nonracial assessment of the relationships of all the peoples of the world, past and present.

Ancestry of a human endogenous retrovirus family

The human endogenous retrovirus type II (HERVII) family of HERV genomes has been found by Southern blot analysis to be characteristic of humans, apes, and Old World monkeys. New World monkeys and prosimians lack HERVII proviral genomes. Cellular DNAs of humans, common chimpanzees, gorillas, and orangutans, but not lesser ape lar gibbons, appear to contain the HERVII-related HLM-2 proviral genome integrated at the same site (HLM-2 maps to human chromosome 1). This suggests that the ancestral HERVII retrovirus(es) entered the genomes of Old World anthropoids by infection after the divergence of New World monkeys (platyrrhines) but before the evolutionary radiation of large hominoids.

Stereophotogrammetric analysis of occlusal morphology of extant hominoid molars: phenetics and function

Because teeth are commonly preserved in the fossil record, dental remains have often been employed in estimating evolutionary relationships among fossil hominoids. This is appropriate, however, only to the extent that dental morphology is phylogenetically informative. I have used phenetic analytic techniques to assess whether hominoid molars are likely to be useful for phylogenetic inference. Thirty-four occlusal landmarks for first and second molars were chosen; seven on each maxillary and ten on each mandibular tooth. Three-dimensional locations of these points were determined from stereophotographs of dental arcades of more than 260 specimens from six taxa (gorilla, chimpanzee, human, orangutan, siamang, and gibbon). Analytic emphasis was on canonical variates analyses of landmark coordinates for mandibular and maxillary second molars, adjusted for intergroup size differences. There is little correspondence between the systematic implications of hominoid molar morphometrics and reliable estimates of evolutionary propinquity based on interhominoid biomolecular similarities. The former seem to have been determined largely by dietary constraints. Although this suggests the possibility of using the protocol employed here to infer diets of fossil hominoids, molar crown measurements seem unlikely to serve well as phylogenetic indicators in the Hominoidea.

Evaluation of the maximum likelihood estimate of the evolutionary tree topologies from DNA sequence data, and the branching order in hominoidea

A maximum likelihood method for inferring evolutionary trees from DNA sequence data was developed by Felsenstein (1981). In evaluating the extent to which the maximum likelihood tree is a significantly better representation of the true tree, it is important to estimate the variance of the difference between log likelihood of different tree topologies. Bootstrap resampling can be used for this purpose (Hasegawa et al. 1988; Hasegawa and Kishino 1989), but it imposes a great computation burden. To overcome this difficulty, we developed a new method for estimating the variance by expressing it explicitly. The method was applied to DNA sequence data from primates in order to evaluate the maximum likelihood branching order among Hominoidea. It was shown that, although the orangutan is convincingly placed as an outgroup of a human and African apes clade, the branching order among human, chimpanzee, and gorilla cannot be determined confidently from the DNA sequence data presently available when the evolutionary rate constancy is not assumed.

Molecular systematics of higher primates: genealogical relations and classification

We obtained 5' and 3' flanking sequences (5.4 kilobase pairs) from the psi eta-globin gene region of the rhesus macaque (Macaca mulatta) and combined them with available nucleotide data. The completed sequence, representing 10.8 kilobase pairs of contiguous noncoding DNA, was compared to the same orthologous regions available for human (Homo sapiens, as represented by five different alleles), common chimpanzee (Pan troglodytes), gorilla (Gorilla gorilla), and orangutan (Pongo pygmaeus). The nucleotide sequence for Macaca mulatta provided the outgroup perspective needed to evaluate better the relationships of humans and great apes. Pairwise comparisons and parsimony analysis of these orthologues clearly demonstrated (i) that humans and great apes share a high degree of genetic similarity and (ii) that humans, chimpanzees, and gorillas form a natural monophyletic group. These conclusions strongly favor a genealogical classification for higher primates consisting of a single family (Hominidae) with two subfamilies (Homininae for Homo, Pan, and Gorilla and Ponginae for Pongo).

DNA hybridization evidence of hominoid phylogeny: results from an expanded data set

The living hominoids are human, the two species of chimpanzees, gorilla, orangutan, and nine species of gibbons. The cercopithecoids (Old World monkeys) are the sister group of the hominoids. A consensus about the phylogeny of the hominoids has been reached for the branching order of the gibbons (earliest) and the orangutan (next earliest), but the branching order among gorilla, chimpanzees, and human remains in contention. In 1984 we presented DNA-DNA hybridization data, based on 183 DNA hybrids, that we interpreted as evidence that the branching order, from oldest to most recent, was gibbons, orangutan, gorilla, chimpanzees, and human. In the present paper we report on an expanded data set totaling 514 DNA hybrids, which supports the branching order given above. The ranges for the datings of divergence nodes are Old World monkeys, 25-34 million years (Myr) ago; gibbons, 16.4-23 Myr ago; orangutan, 12.2-17 Myr ago; gorilla, 7.7-11 Myr ago; chimpanzees-human, 5.5-7.7 Myr ago. The possible effects of differences in age at first breeding are discussed, and some speculations about average genomic rates of evolution are presented.

Evolution of four human Y chromosomal unique sequences

Four cloned unique sequences from the human Y chromosome, two of which are found only on the Y chromosome and two of which are on both the X and Y chromosomes, were hybridized to restriction enzyme-treated DNA samples of a male and a female chimpanzee (Pan troglodytes), gorilla (Gorilla gorilla), and pig-tailed macaque (Macaca nemestrina); and a male orangutan (Pongo pygmaeus) and gibbon (Hylobates lar). One of the human Y-specific probes hybridized only to male DNA among the humans and great apes, and thus its Y linkage and sequence similarities are conserved. The other human Y-specific clone hybridized to male and female DNA from the humans, great apes, and gibbon, indicating its presence on the X chromosome or autosomes. Two human sequences present on both the X and Y chromosomes also demonstrated conservation as indicated by hybridization to genomic DNAs of distantly related species and by partial conservation of restriction enzyme sites. Although conservation of Y linkage can only be demonstrated for one of these four sequences, these results suggest that Y-chromosomal unique sequence genes do not diverge markedly more rapidly than unique sequences located on other chromosomes. However, this sequence conservation may in part be due to evolution while part of other chromosomes.

Polymorphism of the vitamin D binding protein (DBP) among primates: an evolutionary analysis

The distribution of the DBP (vitamin D binding protein) polymorphism is now well characterized among human populations but for primates only limited results are known. The aim of this paper is to describe the electrophoretic polymorphism of this protein among various species. Using three different electrophoretic methods, we are able to detect an unknown polymorphism and to classify the different alleles observed. These results may be used to set an international nomenclature for further comparisons. The different electrophoretic mobilities between Old and New World Monkeys show that: 1) the Cercopithecoïdea are presenting the largest genetic heterogeneity; 2) the DBP among the Galago corresponds to the lowest isoelectric points observed among Primates; 3) during the evolution from nonhuman Primates to Man, the DBP is able to keep its affinity for vitamin D derivatives despite the occurrence of significant molecular modifications; 4) among Anthropoïdea, the electrophoretic patterns of DBP are very close to the human Gc1 proteins. These results show that evolution at the DBP level can be considered as a continuous mechanism of structural modifications. A significant transition occurs during the differentiation between Cercopithecoïdea and Anthropoïdea. It is not too speculative to consider that some electrophoretic forms detected among Gorilla, Pongo, or Pan may be identical to rare variants observed among humans.

A molecular phylogeny of the hominoid primates as indicated by two-dimensional protein electrophoresis

A molecular phylogeny for the hominoid primates was constructed by using genetic distances from a survey of 383 radiolabeled fibroblast polypeptides resolved by two-dimensional electrophoresis (2DE). An internally consistent matrix of Nei genetic distances was generated on the basis of variants in electrophoretic position. The derived phylogenetic tree indicated a branching sequence, from oldest to most recent, of cercopithecoids (Macaca fascicularis), gibbon-siamang, orangutan, gorilla, and human-chimpanzee. A cladistic analysis of 240 electrophoretic characters that varied between ape species produced an identical tree. Genetic distance measures obtained by 2DE are largely consistent with those generated by other molecular procedures. In addition, the 2DE data set appears to resolve the human-chimpanzee-gorilla trichotomy in favor of a more recent association of chimpanzees and humans.

The evolution of large body size in orangutans: A model for hominoid divergence

Recent Miocene fossil discoveries of large hominoids resemble orangutans. Since the evolution of large body size was functionally related to a powerful masticatory system in Miocene ape radiations, a better understanding of adaptations in extant orangutans will be informative of hominoid evolution. It is suggested here, based on the behavioral ecology of extant orangutans, that foraging energetics and large body size are tied to a dietary shift that provided access to and utilization of resources not generally available to other primates.

Evidence for genetic diversity in Trypanosoma (Nannomonas) congolense

Genetic proximity between two karyotypic groups of Trypanosoma congolense was investigated using as hybridization probes: total genomic DNA, a 35 nucleotide long synthetic oligonucleotide, and non-variant antigen type (non-VAT) specific complementary DNAs. The phylogenetic relationship between Trypanosoma brucei and T. evansi, both of which are accepted species in the subgenus Trypanozoon, was used as a reference to assess the phylogenetic proximity of the two groups of T. congolense. Results indicate that some morphologically indistinguishable T. congolense populations differ in a variety of molecular and genetic properties: molecular karyotypes, majority of the DNA sequences, and the restriction enzyme sites in the genomic environments of various conserved genes. The implications of these findings for trypanosome evolution and T. congolense epidemiology are discussed.