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Current Biology : CB Jan 2016The identification and recruitment of trustworthy partners represents an important adaptive challenge for any species that relies heavily on cooperation [1, 2]. From an...
The identification and recruitment of trustworthy partners represents an important adaptive challenge for any species that relies heavily on cooperation [1, 2]. From an evolutionary perspective, trust is difficult to account for as it involves, by definition, a risk of non-reciprocation and defection by cheaters [3, 4]. One solution for this problem is to form close emotional bonds, i.e., friendships, which enable trust even in contexts where cheating would be profitable [5]. Little is known about the evolutionary origins of the human tendency to form close social bonds to overcome the trust problem. Studying chimpanzees (Pan troglodytes), one of our closest living relatives, is one way of identifying these origins. While a growing body of research indicates that at least some of the properties of close human relationships find parallels in the social bonds of chimpanzees [6-10] and that chimpanzees extend favors preferentially toward selected individuals [11-14], it is unclear whether such interactions are based on trust. To fill this gap in knowledge, we observed the social interactions of a group of chimpanzees and established dyadic friendship relations. We then presented chimpanzees with a modified, non-verbal version of the human trust game and found that chimpanzees trust their friends significantly more frequently than their non-friends. These results suggest that trust within closely bonded dyads is not unique to humans but rather has its evolutionary roots in the social relationships of our closest primate relatives.
Topics: Animals; Behavior, Animal; Biological Evolution; Friends; Interpersonal Relations; Pan troglodytes; Social Behavior; Trust
PubMed: 26776735
DOI: 10.1016/j.cub.2015.11.037 -
Communications Biology Jan 2021The paracingulate sulcus -PCGS- has been considered for a long time to be specific to the human brain. Its presence/absence has been discussed in relation to... (Comparative Study)
Comparative Study
The paracingulate sulcus -PCGS- has been considered for a long time to be specific to the human brain. Its presence/absence has been discussed in relation to interindividual variability of personality traits and cognitive abilities. Recently, a putative PCGS has been observed in chimpanzee brains. To demonstrate that this newly discovered sulcus is the homologue of the PCGS in the human brain, we analyzed cytoarchitectonic and resting-state functional magnetic resonance imaging data in chimpanzee brains which did or did not display a PCGS. The results show that the organization of the mid-cingulate cortex of the chimpanzee brain is comparable to that of the human brain, both cytoarchitectonically and in terms of functional connectivity with the lateral frontal cortex. These results demonstrate that the PCGS is not human-specific but is a shared feature of the primate brain since at least the last common ancestor to humans and great apes ~6 mya.
Topics: Animals; Frontal Lobe; Humans; Magnetic Resonance Imaging; Pan troglodytes
PubMed: 33420330
DOI: 10.1038/s42003-020-01571-3 -
Y-Chromosome variation in hominids: intraspecific variation is limited to the polygamous chimpanzee.PloS One 2011We have previously demonstrated that the Y-specific ampliconic fertility genes DAZ (deleted in azoospermia) and CDY (chromodomain protein Y) varied with respect to copy...
BACKGROUND
We have previously demonstrated that the Y-specific ampliconic fertility genes DAZ (deleted in azoospermia) and CDY (chromodomain protein Y) varied with respect to copy number and position among chimpanzees (Pan troglodytes). In comparison, seven Y-chromosomal lineages of the bonobo (Pan paniscus), the chimpanzee's closest living relative, showed no variation. We extend our earlier comparative investigation to include an analysis of the intraspecific variation of these genes in gorillas (Gorilla gorilla) and orangutans (Pongo pygmaeus), and examine the resulting patterns in the light of the species' markedly different social and mating behaviors.
METHODOLOGY/PRINCIPAL FINDINGS
Fluorescence in situ hybridization analysis (FISH) of DAZ and CDY in 12 Y-chromosomal lineages of western lowland gorilla (G. gorilla gorilla) and a single lineage of the eastern lowland gorilla (G. beringei graueri) showed no variation among lineages. Similar findings were noted for the 10 Y-chromosomal lineages examined in the Bornean orangutan (Pongo pygmaeus), and 11 Y-chromosomal lineages of the Sumatran orangutan (P. abelii). We validated the contrasting DAZ and CDY patterns using quantitative real-time polymerase chain reaction (qPCR) in chimpanzee and bonobo.
CONCLUSION/SIGNIFICANCE
High intraspecific variation in copy number and position of the DAZ and CDY genes is seen only in the chimpanzee. We hypothesize that this is best explained by sperm competition that results in the variant DAZ and CDY haplotypes detected in this species. In contrast, bonobos, gorillas and orangutans-species that are not subject to sperm competition-showed no intraspecific variation in DAZ and CDY suggesting that monoandry in gorillas, and preferential female mate choice in bonobos and orangutans, probably permitted the fixation of a single Y variant in each taxon. These data support the notion that the evolutionary history of a primate Y chromosome is not simply encrypted in its DNA sequences, but is also shaped by the social and behavioral circumstances under which the specific species has evolved.
Topics: Animals; Hominidae; In Situ Hybridization, Fluorescence; Pan troglodytes; Real-Time Polymerase Chain Reaction; Species Specificity; Y Chromosome
PubMed: 22216243
DOI: 10.1371/journal.pone.0029311 -
Genes, Brain, and Behavior Apr 2020The vasopressin system has been implicated in the regulation of social behavior and cognition in humans, nonhuman primates and other social mammals. In chimpanzees,...
The vasopressin system has been implicated in the regulation of social behavior and cognition in humans, nonhuman primates and other social mammals. In chimpanzees, polymorphisms in the vasopressin V1a receptor gene (AVPR1A) have been associated with social dimensions of personality, as well as to responses to sociocommunicative cues and mirror self-recognition. Despite evidence of this association with social cognition and behavior, there is little research on the neuroanatomical correlates of AVPR1A variation. In the current study, we tested the association between AVPR1A polymorphisms in the RS3 promotor region and gray matter covariation in chimpanzees using magnetic resonance imaging and source-based morphometry. The analysis identified 13 independent brain components, three of which differed significantly in covariation between the two AVPR1A genotypes (DupB-/- and DupB+/-; P < .05). DupB+/- chimpanzees showed greater covariation in gray matter in the premotor and prefrontal cortex, basal forebrain, lunate and cingulate cortex, and lesser gray matter covariation in the superior temporal sulcus and postcentral sulcus. Some of these regions were previously found to differ in vasopressin and oxytocin neural fibers between nonhuman primates, and in AVPR1A gene expression in humans with different RS3 alleles. This is the first report of an association between AVPR1A and gray matter covariation in nonhuman primates, and specifically links an AVPR1A polymorphism to structural variation in the social brain network. These results further affirm the value of chimpanzees as a model species for investigating the relationship between genetic variation, brain structure and social cognition with relevance to psychiatric disorders, including autism.
Topics: Animals; Cerebral Cortex; Connectome; Genotype; Gray Matter; Pan troglodytes; Polymorphism, Genetic; Promoter Regions, Genetic; Receptors, Vasopressin; Social Behavior
PubMed: 31894656
DOI: 10.1111/gbb.12631 -
Proceedings of the National Academy of... Jan 2020Music and dance are universal across human culture and have an ancient history. One characteristic of music is its strong influence on movement. For example, an auditory...
Music and dance are universal across human culture and have an ancient history. One characteristic of music is its strong influence on movement. For example, an auditory beat induces rhythmic movement with positive emotions in humans from early developmental stages. In this study, we investigated if sound induced spontaneous rhythmic movement in chimpanzees. Three experiments showed that: 1) an auditory beat induced rhythmic swaying and other rhythmic movements, with larger responses from male chimpanzees than female chimpanzees; 2) random beat as well as regular beat induced rhythmic swaying and beat tempo affected movement periodicity in a chimpanzee in a bipedal posture; and 3) a chimpanzee showed close proximity to the sound source while hearing auditory stimuli. The finding that male chimpanzees showed a larger response to sound than female chimpanzees was consistent with previous literature about "rain dances" in the wild, where male chimpanzees engage in rhythmic displays when hearing the sound of rain starting. The fact that rhythmic swaying was induced regardless of beat regularity may be a critical difference from humans, and a further study should reveal the physiological properties of sound that induce rhythmic movements in chimpanzees. These results suggest some biological foundation for dancing existed in the common ancestor of humans and chimpanzees ∼6 million years ago. As such, this study supports the evolutionary origins of musicality.
Topics: Animals; Auditory Perception; Behavior, Animal; Biological Evolution; Dancing; Female; Humans; Male; Movement; Music; Pan troglodytes; Periodicity; Posture; Sex Factors; Sound
PubMed: 31871195
DOI: 10.1073/pnas.1910318116 -
Folia Histochemica Et Cytobiologica 2009Most notably, recent comparative genomic analyses strongly indicate that the marked differences between modern human and chimpanzees are likely due more to changes in...
Most notably, recent comparative genomic analyses strongly indicate that the marked differences between modern human and chimpanzees are likely due more to changes in gene regulation than to modifications of the genes. The most peculiar aspect of hominoid karyotypes is that human have 46 chromosomes whereas gorillas and chimpanzees have 48. Interestingly, human and chimpanzees do share identical inversions on chromosome 7 and 9 that are not evident in the gorilla karyotype. Thus, the general phylogeny suggests that humans and chimpanzees are sister taxa; based on this, it seems that human-chimpanzee sequence similarity is an astonishing 99%. At this purpose, of particular interest is the inactivation of the myosin heavy chain 16 (MYH16) gene, most prominently expressed in the masticatory muscle of mammals. It has been showed that the loss of this gene in humans may have resulted in smaller masticatory muscle and consequential changes to cranio-facial morphology and expansion of the human brain case. Powerful masticatory muscles are found in most primates; contrarily, in both modern and fossil member Homo, these muscles are considerably smaller. The evolving hominid masticatory apparatus shifted towards a pattern of gracilization nearly simultaneously with accelerated encephalization in early Homo. To better comprehend the real role of the MYH16 gene, we studied the primary proteins present in the muscle fibers of humans and non-humans, in order to understand if they really can be influenced by MYH16 gene. At this aim we examined the muscle-specific integrins, alpha 7B and beta 1D-integrins, and their relative fetal isoforms, alpha 7A and beta 1A-integrins, analyzing, by immunohistochemistry, muscle biopsies of two components of a chimpanzee's group in captivity, an alpha male and a non-alpha male subjects; all these integrins participate in vital biological processes such as maintenance of tissue integrity, embryonic development, cell differentiation, and cell-extracellular matrix interactions. Our results demonstrated a different quantitative composition of integrins, in alpha male in respect to human and non-alpha male, hypothesizing that the MYH16 gene could modify the expression of integrins, influencing, in turn, the phenotype of muscle. In this way, alpha 7A-and beta 1A-integrin could determine the presence of type II fibers and then they could play a key role in the determination of contraction force. Then, MYH16 gene could be a common interactor of signalling between sarcoglycans and integrins in chimpanzee muscles.
Topics: Adult; Animals; Humans; Immunohistochemistry; Integrins; Male; Masseter Muscle; Middle Aged; Myosin Heavy Chains; Pan troglodytes; Protein Isoforms; Signal Transduction
PubMed: 20430719
DOI: 10.2478/v10042-009-0095-3 -
Brain Structure & Function Mar 2017The evolution of neurocranial morphology in Homo sapiens is characterized by bulging of the parietal region, a feature unique to our species. In modern humans, expansion...
The evolution of neurocranial morphology in Homo sapiens is characterized by bulging of the parietal region, a feature unique to our species. In modern humans, expansion of the parietal surface occurs during the first year of life, in a morphogenetic stage which is absent in chimpanzees and Neandertals. A similar variation in brain shape among living adult humans is associated with expansion of the precuneus. Using MRI-derived structural brain templates, we compare medial brain morphology between humans and chimpanzees through shape analysis and geometrical modeling. We find that the main spatial difference is a prominent expansion of the precuneus in our species, providing further evidence of evolutionary changes associated with this area. The precuneus is a major hub of brain organization, a central node of the default-mode network, and plays an essential role in visuospatial integration. Together, the comparative neuroanatomical and paleontological evidence suggest that precuneus expansion is a neurological specialization of H. sapiens that evolved in the last 150,000 years that may be associated with recent human cognitive specializations.
Topics: Adult; Animals; Biological Evolution; Humans; Image Processing, Computer-Assisted; Magnetic Resonance Imaging; Pan troglodytes; Parietal Lobe; Species Specificity
PubMed: 26725108
DOI: 10.1007/s00429-015-1172-y -
Proceedings of the National Academy of... Jan 2017Intergroup conflict is evident throughout the history of our species, ubiquitous across human societies, and considered crucial for the evolution of humans' large-scale...
Intergroup conflict is evident throughout the history of our species, ubiquitous across human societies, and considered crucial for the evolution of humans' large-scale cooperative nature. Like humans, chimpanzee societies exhibit intragroup coordination and coalitionary support during violent intergroup conflicts. In both species, cooperation among group members is essential for individuals to gain access to benefits from engaging in intergroup conflict. Studies suggest that a contributive mechanism regulating in-group cooperation during intergroup conflicts in humans involves the neuropeptide hormone oxytocin, known to influence trust, coordination, and social cognition, although evidence from natural settings is lacking. Here, applying a noninvasive method, we investigate oxytocinergic system involvement during natural intergroup conflicts in wild chimpanzees. We found that chimpanzees of both sexes had significantly higher urinary oxytocin levels immediately before and during intergroup conflict compared with controls. Also, elevated hormone levels were linked with greater cohesion during intergroup conflicts, rather than with the level of potential threat posed by rival groups, intragroup affiliative social interactions, or coordinated behavior alone. Thus, the oxytocinergic system, potentially engendering cohesion and cooperation when facing an out-group threat, may not be uniquely human but rather a mechanism with evolutionary roots shared by our last common ancestor with chimpanzees, likely expediting fitness gains during intergroup conflict.
Topics: Aggression; Altruism; Animals; Behavior, Animal; Conflict, Psychological; Cooperative Behavior; Female; Group Processes; Interpersonal Relations; Male; Oxytocin; Pan troglodytes; Social Behavior; Trust
PubMed: 28028227
DOI: 10.1073/pnas.1616812114 -
Journal of Comparative Psychology... Nov 2012The accurate recognition of individuals is a cornerstone of social exchange in primates. Current approaches to the study of individual recognition, however, are focused...
The accurate recognition of individuals is a cornerstone of social exchange in primates. Current approaches to the study of individual recognition, however, are focused on human performance and only occasionally reference comparative research for support. A number of studies have suggested that humans can easily recognize thousands of individual faces and that this perceptual expertise is supported by holistic processing, a phenomenon best demonstrated by the composite face effect (CFE). Recent advances have indicated that the CFE in humans is robust to changes in contrast polarity (positive or negative). Here we apply a two alternative forced choice match-to-sample paradigm across two species of nonhuman primate, chimpanzees (Pan troglodyte) and rhesus monkeys (Macaca mulatta). We find strong evidence that chimpanzees and rhesus monkeys experience interference from holistic processing in the positive contrast condition. While there is some indication that the chimpanzees experienced a CFE in the negative contrast condition, there was no evidence of a CFE in the corresponding rhesus monkey data. These results suggest that, while holistic processing is a general mechanism, rhesus monkeys are more sensitive to contrast-polarity than humans.
Topics: Animals; Face; Female; Macaca mulatta; Male; Pan troglodytes; Pattern Recognition, Visual; Photic Stimulation; Recognition, Psychology
PubMed: 22390621
DOI: 10.1037/a0027287 -
Journal of Comparative Psychology... Aug 2007Two major theoretical approaches have dominated the quest for uniquely human cognitive abilities: a developmentalist approach stressing the importance of environmental... (Review)
Review
Two major theoretical approaches have dominated the quest for uniquely human cognitive abilities: a developmentalist approach stressing the importance of environmental and social conditions, and a predominant approach in experimental and comparative psychology, the deterministic approach suggesting the effect of environmental and social conditions to be minimal. As a consequence, most claims of human cognitive uniqueness are based on comparisons of White middle class Westerner humans (Homo sapiens) with captive chimpanzees (Pan troglodytes). However, humans are much more than only White middle class Westerners, and chimpanzees are much more than only captives. A review of some data available on different populations of humans and chimpanzees reveals that only the predictions of the developmentalist approach are supported. In addition, systematic biases are too often introduced in experiment protocols when comparing humans with apes that further cast doubts on cross-species comparisons. The author argues that only with consideration of within-species population differences in the cognitive domains and the use of well-matched cross-species experimental procedures will an objective understanding of the different cognitive abilities between species emerge. This will require a shift in the theoretical approach adopted by many in experimental and comparative psychology.
Topics: Animals; Cognition; Developmental Biology; Environment; Pan troglodytes; Socioeconomic Factors; Space Perception; Species Specificity; Humans
PubMed: 17696649
DOI: 10.1037/0735-7036.121.3.227