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PubMed1996

Structure and content of the major histocompatibility complex (MHC) class I regions of the great anthropoid apes.

The origins of the functional class I genes predated human speciation, a phenomenon known as trans-speciation. The retention of class Ia orthologues within the great apes, however, has not been paralleled by studies designed to examine the pseudogene content, organization, and structure of their class I regions. Therefore, we have begun the systematic characterization of the Old World primate MHCs. The numbers and sizes of fragments harboring class I sequences were similar among the chimpanzee, gorilla, and human genomes tested. Both of the gorillas included in our study possessed genomic fragments carrying orthologues of the recently evolved HLA-H pseudogene identical to those found in the human. The overall megabase restriction fragment patterns of humans and chimpanzees appeared slightly more similar to each other, although the HLA-A subregional megabase variants may have been generated following the emergence of Homo sapiens. Based on the results of this initial study, it is difficult to generate a firm species tree and to determine human's closest evolutionary neighbor. Nevertheless, an analysis of MHC subregional similarities and differences in the hominoid apes may ultimately aid in localizing and identifying MHC haplotype-associated disease genes such as idiopathic hemochromatosis.

Animals↗
PubMed1985

The Aquatic Ape Theory: evidence and a possible scenario.

Much more than other primates, man has several features that are seen more often in aquatic than terrestrial mammals: nakedness, thick subcutaneous fat-layer, stretched hindlimbs, voluntary respiration, dilute urine etc. The Aquatic Ape Theory states that our ancestors once spent a significant part of their life in water. Presumably, early apes were plant and fruit eaters in tropical forests. Early hominids also ate aquatic food; at first mainly weeds and tubers, later sea shore animals, especially shellfish. With the Pleistocene cooling, our ancestors returned to land and became bipedal omnivores and scavengers and later hunters of coastal and riverside animals.

Adaptation, Biological↗
PubMed2004

Polymorphism in the second intron of dopamine receptor D4 gene in humans and apes.

The dopamine receptor D4 (DRD4) has received increasing research attention in behavioral science, psychiatry, and psychopharmacology. However, the number of available genetic markers for primates is still insufficient. We identified a novel variation/polymorphism in the second intron of DRD4 in humans based on the survey of 210 Japanese: a 6bp insertion (allele frequency: 0.002) and 8bp deletion (0.024); however, 94 Hungarian Caucasians were found to be monomorphic. Polymorphisms of the homologous region were also found in a survey of 93 specimens from four species of great apes and 51 specimens from seven species of gibbons. The polymorphisms consist of both single nucleotide substitutions and variations in the number of tandem duplications of short GC-rich sequences. Because of usefulness of primates in behavioral science, this polymorphism may be a useful marker for association studies with behavioral traits in both humans and apes.

Animals↗
PubMed2005

From the ape's dilemma to the weanling's dilemma: early weaning and its evolutionary context.

Although humans have a longer period of infant dependency than other hominoids, human infants, in natural fertility societies, are weaned far earlier than any of the great apes: chimps and orangutans wean, on average, at about 5 and 7.7 years, respectively, while humans wean, on average, at about 2.5 years. Assuming that living great apes demonstrate the ancestral weaning pattern, modern humans display a derived pattern that requires explanation, particularly since earlier weaning may result in significant hazards for a child. Clearly, if selection had favored the survival of the child, humans would wean later like other hominoids; selection, then, favored some trait other than the child's survival. It is argued here that our unique pattern of prolonged, early brain growth--the neurological basis for human intellectual ability--cannot be sustained much beyond one year by a human mother's milk alone, and thus early weaning, when accompanied by supplementation with more nutritious adult foods, is vital to the ontogeny of our larger brain, despite the associated dangers. Therefore, the child's intellectual development, rather than its survival, is the primary focus of selection. Consumption of more nutritious foods--derived from animal protein--increased by ca. 2.6 myr ago when a group of early hominins displayed two important behavioral shifts relative to ancestral forms: the recognition that a carcass represented a new and valuable food source-potentially larger than the usual hunted prey-and the use of stone tools to improve access to that food source. The shift in the hominin "prey image" to the carcass and the use of tools for butchery increased the amount of protein and calories available, irrespective of the local landscape. However, this shift brought hominins into competition with carnivores, increasing mortality among young adults and necessitating a number of social responses, such as alloparenting. The increased acquisition of meat ca. 2.6 Ma had significant effects on the later course of human evolution and may have initiated the origin of the genus Homo.

Aging↗
PubMed2006

Reliance on head versus eyes in the gaze following of great apes and human infants: the cooperative eye hypothesis.

As compared with other primates, humans have especially visible eyes (e.g., white sclera). One hypothesis is that this feature of human eyes evolved to make it easier for conspecifics to follow an individual's gaze direction in close-range joint attentional and communicative interactions, which would seem to imply especially cooperative (mututalistic) conspecifics. In the current study, we tested one aspect of this cooperative eye hypothesis by comparing the gaze following behavior of great apes to that of human infants. A human experimenter "looked" to the ceiling either with his eyes only, head only (eyes closed), both head and eyes, or neither. Great apes followed gaze to the ceiling based mainly on the human's head direction (although eye direction played some role as well). In contrast, human infants relied almost exclusively on eye direction in these same situations. These results demonstrate that humans are especially reliant on eyes in gaze following situations, and thus, suggest that eyes evolved a new social function in human evolution, most likely to support cooperative (mututalistic) social interactions.

Animals↗
PubMed2005

A five-link 2D brachiating ape model with life-like zero-energy-cost motions.

We have found periodic life-like brachiating motions of a rigid-body ape model that use no muscle or gravitational energy to move steadily forward. The most complicated of these models has 5 links (a body and two arms, each with 2 links) and 7 degrees of freedom in flight. The defining feature of all our periodic solutions is that all collisions are at zero relative velocity. These motions are found using numerical integration and root-finding that is sufficiently precise so as to imply that the solutions found correspond to mathematical solutions with exactly zero energy cost. The only actuation and control in the model is for maintaining contact with and releasing handholds which requires no mechanical work. The similarity of these energy-free simulations to the motions of apes suggests that muscle-use minimization at least partially characterizes the coordination strategies they use.

Animals↗
PubMed2006

Rational versus anti-rational interpretations of science: an ape-language case-study.

Robert Nola (2003) has argued that anti-rationalist interpretations of science fail to adequately explain the process of science, since objective reasons can be causal factors in belief formation. While I agree with Nola that objective reasons can be a cause of belief, in this paper I present a version of the strong programme in the sociology of knowledge, the Interests Thesis, and argue that the Interests Thesis provides a plausible explanation of an episode in the history of ape-language research. Specifically, I examine Terrace, Petitto, Sandess, & Bever (1979, 1980) illegitimate comparison of the signing of their chimpanzee, Nim, with data from human early childhood language development, and argue that Terrace et al.'s interests played a causal role in determining their sceptical beliefs concerning ape linguistic abilities. However, I go on to argue that Terrace et al.'s interests are not the only causal factors in determining their beliefs: objective reasons, associated with the institution of new methodologies, were also causally determinative of Terrace et al.'s sceptical beliefs. Consequently, I argue that belief formation in science is a multi-factorial affair wherein both interests and objective reasons have causal roles. I finish the paper with two conjectures concerning the proper locus of scientific rationality.

Animal Communication↗
PubMed2003

Are planum temporale and sylvian fissure asymmetries directly related? A MRI study in great apes.

In humans and great apes, both the planum temporale (PT-part of Wernicke's area) and the sylvian fissure (SF) in the left cerebral hemisphere have been consistently shown to be larger than the corresponding structures in the right hemisphere. The greater length of the SF in the left hemisphere is commonly thought to be a direct consequence of the larger expansion of the PT in the same hemisphere. However, there is a lack of studies that have attempted to directly assess the tenability of this hypothesis. To address this lack of data, we collected magnetic resonance images (MRI) of the brain in 28 apes. The surface area of the PT and the length of the pre- and post-central SF were measured in each hemisphere using image acquisition and analysis software. In accordance with previous findings, the PT was markedly larger in the left hemisphere than in the right, and there was also a leftward asymmetry of the SF, particularly of its post-central section. However, we found no statistically significant correlation between asymmetry of the PT and of the post-central SF, whereas we did find evidence of a positive association between asymmetry of the post-central SF and of the inferior parietal lobe. These results are congruent with those of a recent study with human subjects [Neuropsychiatry, Neuropsychology and Behavioral Neurology 12 (1999) 1]. Overall, this converging evidence leads us to question the widely accepted notion of a direct relationship between PT and SF asymmetries and to consider possible implications of this finding for the study of the evolutionary origin of PT asymmetry in primates.

Animals↗
PubMed1997

Alternative splicing in lecithin:cholesterol acyltransferase mRNA: an evolutionary paradigm in humans and great apes.

Lecithin:cholesterol acyltransferase (LCAT), an important enzyme affecting reverse cholesterol transport, is expressed in liver and cultured fibroblasts. Sequencing of LCAT cDNA clones demonstrated the coexistence of two mRNA products. In addition to the normal transcript, we identified an alternate message with a splice-mediated insertion of a 95 bp Alu cassette at the junction of exons 5 and 6. In humans, the alternate transcript represents 5-20% of the complete LCAT message in cultured fibroblasts and liver. It is present in humans and the great apes but not in lesser apes (gibbon, siamang) or lower-order primates (e.g., old or new world monkeys). Sequencing of intron 5 of the LCAT locus in several primates revealed a G-->A transition at the splice donor recognition site in the Alu repeat of the gibbon and a G-->A substitution in the last position of the 95 bp Alu sequence of the rhesus monkey, an old world monkey. Both substitutions have been associated with exon skipping in other genes. These results demonstrate that alternative splicing of LCAT mRNA is variant among primates and suggest a potential role of Alu elements in the evolutionary diversity of proteins.

Alternative Splicing↗
PubMed2004

A geometric morphometric assessment of hominoid crania: conservative African apes and their liberal implications.

This study examined the cranial affinities of all extant hominoids using 3D geometric morphometric analysis. A least squares Procrustean superimposition was used to eliminate differences due to location, orientation, and size. Because of a persistent correlation between centroid size and shape variation, an allometric size adjustment was also applied to these data. Phenetic affinities were then examined through a battery of multivariate statistical analyses. Results of this study indicate a strong affinity between Hylobates and Gorilla; Pan is also similar to these genera, while Pongo and Homo are each very different. The autapomorphic morphologies of orangutan and modern human crania have been well established from previous studies. The similarity between Hylobates and Gorilla, however, has important implications for studies of hominoid morphology. First, these results suggest that African ape crania--and particularly those of Gorilla--retain an overall morphology that is conservative among hominoids. Secondly, this similarity suggests that character coding of cranial features may tend to overestimate the degree of polymorphism among extant apes. This study concludes that allometry may play a greater role in the morphogenesis of hominoid cranial variation than has been previously thought. While this problem likely has negligible impact on systematic studies of extant hominoids, it seriously affects our ability to place fossil taxa within a phylogenetic framework.

Animals↗
PubMed2005

All great ape species follow gaze to distant locations and around barriers.

Following the gaze direction of conspecifics is an adaptive skill that enables individuals to obtain useful information about the location of food, predators, and group mates. In the current study, the authors compared the gaze-following skills of all 4 great ape species. In the 1st experiment, a human either looked to the ceiling or looked straight ahead. Individuals from all species reliably followed the human's gaze direction and sometimes even checked back when they found no target. In a 2nd experiment, the human looked behind some kind of barrier. Results showed that individuals from all species reliably put themselves in places from which they could see what the experimenter was looking at behind the barrier. These results support the hypothesis that great apes do not just orient to a target that another is oriented to, but they actually attempt to take the visual perspective of the other.

Animals↗
PubMed2001

Positive selection of a gene family during the emergence of humans and African apes.

Gene duplication followed by adaptive evolution is one of the primary forces for the emergence of new gene function. Here we describe the recent proliferation, transposition and selection of a 20-kilobase (kb) duplicated segment throughout 15 Mb of the short arm of human chromosome 16. The dispersal of this segment was accompanied by considerable variation in chromosomal-map location and copy number among hominoid species. In humans, we identified a gene family (morpheus) within the duplicated segment. Comparison of putative protein-encoding exons revealed the most extreme case of positive selection among hominoids. The major episode of enhanced amino-acid replacement occurred after the separation of human and great-ape lineages from the orangutan. Positive selection continued to alter amino-acid composition after the divergence of human and chimpanzee lineages. The rapidity and bias for amino-acid-altering nucleotide changes suggest adaptive evolution of the morpheus gene family during the emergence of humans and African apes. Moreover, some genes emerge and evolve very rapidly, generating copies that bear little similarity to their ancestral precursors. Consequently, a small fraction of human genes may not possess discernible orthologues within the genomes of model organisms.

Animals↗
PubMed2002

Strong male-driven evolution of DNA sequences in humans and apes.

Studies of human genetic diseases have suggested a higher mutation rate in males than in females and the male-to-female ratio (alpha) of mutation rate has been estimated from DNA sequence and microsatellite data to be about 4-6 in higher primates. Two recent studies, however, claim that alpha is only about 2 in humans. This is even smaller than the estimates (alpha > 4) for carnivores and birds; humans should have a higher alpha than carnivores and birds because of a longer generation time and a larger sex difference in the number of germ cell cycles. To resolve this issue, we sequenced a noncoding fragment on Y of about 10.4 kilobases (kb) and a homologous region on chromosome 3 in humans, greater apes, and lesser apes. Here we show that our estimate of alpha from the internal branches of the phylogeny is 5.25 (95% confidence interval (CI) 2.44 to infinity), similar to the previous estimates, but significantly higher than the two recent ones. In contrast, for the external (short, species-specific) branches, alpha is only 2.23 (95% CI: 1.47-3.84). We suggest that closely related species are not suitable for estimating alpha, because of ancient polymorphism and other factors. Moreover, we provide an explanation for the small estimate of alpha in a previous study. Our study reinstates a high alpha in hominoids and supports the view that DNA replication errors are the primary source of germline mutation.

Animals↗
PubMed2002

Humans and great apes share a large frontal cortex.

Some of the outstanding cognitive capabilities of humans are commonly attributed to a disproportionate enlargement of the human frontal lobe during evolution. This claim is based primarily on comparisons between the brains of humans and of other primates, to the exclusion of most great apes. We compared the relative size of the frontal cortices in living specimens of several primate species, including all extant hominoids, using magnetic resonance imaging. Human frontal cortices were not disproportionately large in comparison to those of the great apes. We suggest that the special cognitive abilities attributed to a frontal advantage may be due to differences in individual cortical areas and to a richer interconnectivity, none of which required an increase in the overall relative size of the frontal lobe during hominid evolution.

Animals↗
PubMed1981

Molecular cloning and partial characterization of unintegrated linear DNA from gibbon ape leukemia virus.

We have cloned the complete genome of an oncogenic primate retrovirus, the San Francisco isolate of gibbon ape leukemia virus, in a lambda phage vector. DNA sequence analysis and restriction endonuclease mapping of the inserted linear provirus demonstrated 9-base pair inverted repeats at its ends, flanking direct terminal repeats 470 base pairs in length. The (-) strong stop region of this DNA showed surprisingly low sequence homology to that of another gibbon ape leukemia virus isolate from an animal with similar disease. Analysis of the clone also revealed the terminal phosphate configuration of the linear provirus. The recombinant phage is suitable for direct use as a hybridization probe to detect homologous retroviral sequences in human cell lines.

Animals↗
PubMed1986

Insertion and/or deletion of many repeated DNA sequences in human and higher ape evolution.

The total numbers of copies of two repeat families, L1 (Kpn I) and Alu, have been measured in the DNA of four higher apes by an accurate titration method. The number of members of the Alu family repeats in the four genomes are as follows: human, 910,000; chimpanzee, 330,000; gorilla, 410,000; orangutan, 580,000. For the Kpn I family (3'-ward higher frequency region) the number of copies in these genomes are as follows: human, 107,000; chimpanzee, 51,000; gorilla, 64,000; orangutan, 84,000. Thermal stability measurements show that, although the families of repeats are moderately divergent in sequence, little net sequence change has occurred during the evolution of the higher apes. Most or all of the members of these families of repeats are interspersed throughout the genome. Therefore, a large number of events of insertion and/or deletion of these DNA sequences has occurred during higher primate evolution.

Animals↗
PubMed1991

Gene sequences suggest inactivation of alpha-1,3-galactosyltransferase in catarrhines after the divergence of apes from monkeys.

The glycosylation enzyme alpha-1,3-galactosyltransferase (alpha 1,3GT; UDPgalactose:beta-D-galactosyl-1,4-N-acetyl-D-glucosaminide alpha-1,3-galactosyltransferase, EC 2.4.1.151) displays a unique pattern of distribution in mammals. It synthesizes an abundance of Gal(alpha 1-3)Gal(beta 1-4)GlcNAc-R (alpha-galactosyl) epitopes within the Golgi apparatus of cells of nonprimate mammals, prosimians, and New World monkeys (platyrrhines). The catarrhines, which include Old World monkeys, apes, and humans, lack this enzyme activity because of the inactivation of the alpha 1,3GT gene. In contrast, the catarrhines produce large amounts of antibodies, designated anti-Gal, against the alpha-galactosyl epitope. The inactivation of the alpha 1,3GT gene in ancestral catarrhines was probably the result of an intensive evolutionary pressure for alteration in the makeup of cell surface carbohydrates (i.e., suppression of alpha-galactosyl epitope expression) and for the production of the anti-Gal antibody. To determine the period in which the alpha 1,3GT gene was inactivated in ancestral catarrhines, comparative sequencing of a 370-base-pair region of this gene was performed by polymerase chain reactions with DNA of various primates. The data suggest that alpha 1,3GT inactivation occurred rather late in the course of catarrhine evolution (less than 28 million years ago), as separate events in apes and in Old World monkeys, after the two groups diverged from each other.

Animals↗
PubMed1993

Recently recovered Kenyapithecus mandible and its implications for great ape and human origins.

We report here a Kenyapithecus africanus juvenile mandible recovered from middle Miocene (ca. 14-16 million years) deposits of Maboko Island (Lake Victoria), Kenya. Symphyseal and dental attributes of the mandible distinguish K. africanus, a species widely regarded as the earliest known member of the great ape and human clade, from other Miocene large-bodied hominoids. The Maboko Island mandible exhibits a markedly proclined symphyseal axis, massive inferior transverse torus, mesiodistally narrow, high-crowned, and strongly procumbent lateral incisor, and molars with cingula restricted to the median buccal cleft. Although the presence of some of these conditions in Kenyapithecus was suggested earlier, the fragmentary and ill-preserved nature of previously known specimens led certain authorities to doubt their validity. Our assessment of mandibular and dental morphology indicates that K. africanus diverged after Proconsul and Griphopithecus but prior to the last common ancestor of Sivapithecus, extant great apes, and humans. The robustly constructed mandibular symphysis and anterior dentition suggest that incisal biting played as important a role as thick molar enamel in the dietary adaptations of K. africanus.

Animals↗