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1.
Evol Anthropol ; 28(6): 321-331, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31691443

RESUMO

The importance of warfare for human evolution is hotly debated in anthropology. Some authors hypothesize that warfare emerged at least 200,000-100,000 years BP, was frequent, and significantly shaped human social evolution. Other authors claim that warfare is a recent phenomenon, linked to the emergence of agriculture, and mostly explained by cultural rather than evolutionary forces. Here I highlight and critically evaluate six controversial points on the evolutionary bases of warfare. I argue that cultural and evolutionary explanations on the emergence of warfare are not alternative but analyze biological diversity at two distinct levels. An evolved propensity to act aggressively toward outgroup individuals may emerge irrespective of whether warfare appeared early/late during human evolution. Finally, I argue that lethal violence and aggression toward outgroup individuals are two linked but distinct phenomena, and that war and peace are complementary and should not always be treated as two mutually exclusive behavioral responses.


Assuntos
Agressão , Evolução Cultural/história , Guerra/etnologia , Animais , Antropologia , Comportamento Animal/fisiologia , História Antiga , Hominidae/fisiologia , Humanos , Pan troglodytes/fisiologia , Comportamento Social/história
2.
Evol Anthropol ; 28(6): 303-320, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31418959

RESUMO

To understand how our brain evolved and what it is for, we are in urgent need of knowledge about the cognitive skills of a large variety of animal species and individuals, and their relationships to rapidly disappearing social and ecological conditions. But how do we obtain this knowledge? Studying cognition in the wild is a challenge. Field researchers (and their study subjects) face many factors that can easily interfere with their variables of interest. Although field studies of cognition present unique challenges, they are still invaluable for understanding the evolutionary drivers of cognition. In this review, I discuss the advantages and urgency of field-based studies on animal cognition and introduce a novel observational approach for field research that is guided by three questions: (a) what do animals fail to find?, (b) what do they not do?, and (c) what do they only do when certain conditions are met? My goal is to provide guidance to future field researchers examining primate cognition.


Assuntos
Antropologia/métodos , Comportamento Apetitivo/fisiologia , Técnicas de Observação do Comportamento/métodos , Encéfalo/fisiologia , Cognição/fisiologia , Animais , Evolução Biológica , Pan troglodytes/fisiologia
3.
Behav Processes ; 167: 103911, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31374226

RESUMO

Longitudinal research on manual preferences in humans and non-human primates has mainly been conducted from a developmental perspective, with only a few studies exploring long-term stability of this trait during adulthood. Therefore, we investigated short-term (1 year) and long-term (10 and 11 years) consistency of hand preference in a naturalistic group of 19 juvenile and adult chimpanzees (Pan troglodytes) by using two experimental tasks, one unimanual (simple reaching) and one bimanual (tube task). The experimental sessions were conducted in 2007, 2008 and 2018. We found that the direction of hand preference (right vs. left) in the tube task remained stable after both short-time and long-time periods. Conversely, hand preference direction for simple reaching was not consistent after the longest period (11 years), but the handedness indices (HI) between 2007 and 2008 (1-year period) and between 2008 and 2018 (10-year period) were positively correlated. The comparison between tasks confirmed that all the chimpanzees were more strongly lateralised for the tube task. Interestingly, however, the strength of hand preference in the tube task showed an increasing trend in the long term. We hypothesize that this could be a consequence of practice and experience with a particular motor action.


Assuntos
Lateralidade Funcional/fisiologia , Pan troglodytes/fisiologia , Desempenho Psicomotor/fisiologia , Animais , Feminino , Masculino , Primatas , Fatores de Tempo
4.
Hum Nat ; 30(3): 299-325, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31236773

RESUMO

Humans are strongly lateralized for manual gestures at both individual and population levels. In contrast, the laterality bias in primates is less strong, leading some to suggest that lateralization evolved after the Pan and Homo lineages diverged. However, laterality in humans is also context-dependent, suggesting that observed differences in lateralization between primates and humans may be related to external factors such as the complexity of the social environment. Here we address this question in wild chimpanzees and examine the extent to which the laterality of manual gestures is associated with social complexity. Right-handed gestures were more strongly associated with goal-directed communication such as repair through elaboration in response to communication failure than left-handed gestures. Right-handed gestures occurred in evolutionarily urgent contexts such as in interactions with central individuals in the network, including grooming reciprocity and mating, whereas left-handed gestures occurred in less-urgent contexts, such as travel and play. Right-handed gestures occurred in smaller parties and in the absence of social competition relative to left-handed gestures. Right-handed gestures increased the rate of activities indicating high physiological arousal in the recipient, whereas left-handed gestures reduced it. This shows that right- and left-handed gestures differ in cognitive and social complexity, with right-handed gestures facilitating more complex interactions in simpler social settings, whereas left-handed gestures facilitate more rewarding interactions in complex social settings. Differences in laterality between other primates and humans are likely to be driven by differences in the complexity of both the cognitive skills underpinning social interactions and the social environment.


Assuntos
Comunicação Animal , Lateralidade Funcional/fisiologia , Gestos , Pan troglodytes/fisiologia , Comportamento Social , Animais , Animais Selvagens , Feminino , Masculino
5.
Am J Vet Res ; 80(6): 547-557, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31140849

RESUMO

OBJECTIVE: To comprehensively characterize cardiac structure and function, from infancy to adulthood, in male and female wild-born captive chimpanzees (Pan troglodytes) living in sanctuaries. ANIMALS: 290 wild-born captive chimpanzees. PROCEDURES: Physical and echocardiographic examinations were performed on anesthetized chimpanzees in 3 sanctuaries in Africa between October 2013 and May 2017. Results were evaluated across age groups and between sexes, and potential differences were assessed with multiple 1-way independent Kruskal-Wallis tests. RESULTS: Results indicated that left ventricular diastolic and systolic function declined at a younger age in males than in females. Although differences in right ventricular diastolic function were not identified among age groups, right ventricular systolic function was lower in adult chimpanzees (> 12 years old), compared with subadult (8 to 12 years old) and juvenile (5 to 7 years old) chimpanzees. In addition, male subadult and adult chimpanzees had larger cardiac wall dimensions and chamber volumes than did their female counterparts. CONCLUSIONS AND CLINICAL RELEVANCE: Results of the present study provided useful reference intervals for cardiac structure and function in captive chimpanzees categorized on the basis of age and sex; however, further research is warranted to examine isolated and combined impacts of blood pressure, age, body weight, and anesthetic agents on cardiac structure and function in chimpanzees.


Assuntos
Coração/fisiologia , Pan troglodytes/fisiologia , Envelhecimento , Animais , Animais Selvagens , Animais de Zoológico , Pressão Sanguínea , Peso Corporal , Ecocardiografia/veterinária , Feminino , Coração/anatomia & histologia , Masculino , Pan troglodytes/anatomia & histologia , Valores de Referência
6.
Primates ; 60(4): 333-338, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31006043

RESUMO

Although infanticide by wild adult male chimpanzees has been reported from multiple sites, affiliative infant carrying by males is rare. We observed infant carrying by an alpha male chimpanzee at Bulindi (Uganda) on two consecutive mornings and collected faecal samples from the newborn infant female, her mother and all candidate fathers to determine whether the alpha male was the infant's father using a likelihood-based method of paternity assignment. In contrast to previous observations of male care of orphans, in this case the mother was present during observations. Further, unlike reports of male aggression towards infants, the infant was reunited with her mother on the third morning, and survived. Neither mother nor infant presented visible injuries. The alpha male never directed aggression towards the infant. Rather, he displayed attentive behaviours, for example by holding the infant to his chest, supporting her while moving, grooming her, and 'cuddling' and 'rocking' her. Paternity results revealed with a high degree of certainty that the alpha male was the infant's father. There are several alternative explanations for the male's behaviour, but this unusual case also highlights the need for further studies to determine under what circumstances adult male chimpanzees can recognise their own offspring.


Assuntos
Comportamento Animal , Pai , Pan troglodytes/fisiologia , Fatores Etários , Animais , Atenção , Feminino , Asseio Animal , Masculino , Mães , Uganda
7.
Primates ; 60(4): 367-373, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31006044

RESUMO

Digging for underground storage organs of plants has been reported in various populations of wild chimpanzees (Pan troglodytes). However, it is unknown so far whether chimpanzees display lateral biases in manual digging as direct observations of this behavior are still lacking. It was therefore the aim of the present study to assess, for the first time, hand preferences for digging in a group of nine captive chimpanzees. We found that with only one exception, all individuals engaged in manual digging for buried food. Five individuals displayed a significant right-hand preference, two a significant left-hand preference, and one was ambidextrous. No apparent differences between males and females were found with regard to the direction or strength of hand preferences for manual digging. Only one out of four parent-offspring pairs was congruent in their preferred hand for manual digging. Three of the eight chimpanzees who dug manually also used tools in order to excavate buried food. Among those three individuals, one displayed a significant right-, one a significant left-hand preference, and one was ambidextrous. Only one of these three chimpanzees was consistent in preferring the same hand for manual and tool digging. The present findings are in line with the notion that chimpanzees display significant hand preferences at the individual level for haptic-guided behaviors, with a tendency for the right hand.


Assuntos
Comportamento Alimentar , Mãos , Pan troglodytes/fisiologia , Comportamento de Utilização de Ferramentas , Animais , Animais de Zoológico , Feminino , Lateralidade Funcional , Masculino
8.
Primates ; 60(4): 355-365, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-30982104

RESUMO

Human activities impact the distribution of numerous species. Anthropogenic habitats are often fragmented, and wildlife must navigate through human-influenced and 'natural' parts of the landscape to access resources. Different methods to determine the home-range areas of nonhuman primates have not considered the additional complexities of ranging in anthropogenic areas. Here, using 6 months of spatial data on the distribution of chimpanzee presence (feces, feeding traces, nests, opportunistic encounters; n = 833) collected across the wet and dry seasons, we examine different analytical techniques to calculate the home-range size of an unhabituated chimpanzee (Pan troglodytes verus) community inhabiting a forest-farm mosaic at Madina, Cantanhez National Park in Guinea-Bissau. The minimum convex polygon method and the grid cell (500 m × 500 m cell size) method estimated the chimpanzees home-range size at 19.02 and 15.50 km2, respectively with kernel analysis calculating a lower value of 8.52 km2. For the grid cell method, home-range estimates varied with cell size, with larger cells producing larger estimates. We compare our home-range estimates with other chimpanzee research sites across Africa. We recommend the use of kernel analysis for determining primate home ranges, especially for those groups exploiting fragmented habitats including forest-farm mosaics, as this method takes account of inaccessible or infrequently used anthropogenic areas across the complete home range of the primate group. However, care must be taken when using this method, since it is sensitive to small sample sizes that can occur when studying unhabituated communities, resulting in underestimated home ranges.


Assuntos
Comportamento Animal , Fazendas , Florestas , Comportamento de Retorno ao Território Vital , Pan troglodytes/fisiologia , Animais , Ecossistema , Guiné-Bissau , Parques Recreativos , Estações do Ano
9.
Folia Primatol (Basel) ; 90(2): 77-88, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30814479

RESUMO

Data from a large cross-sectional sample of wild chimpanzee mother-infant dyads yield evidence that young chimpanzees' pant grunting unfolds nonlinearly over the early developmental period. Though infants begin pant grunting early, and mothers' rates did not decrease, infant pant grunting declined as infants aged through infancy. Mother-infant dyadic pant grunting discordance therefore increased over infancy, with some discordance observed at even the earliest ages. In half of 90 observed instances involving infants ranging in age from 2 weeks to 69 months, only one member of the mother-infant dyad pant grunted; infants' pant grunting was not influenced by their mother's age, their position on their mother's body at the time of the greeting, or the dominance status of the male greeted. Male infants were more likely to pant grunt than female infants. We discuss the developmental trend in the context of infants' increasing independence, changing social motivations, and male-dominated social hierarchy.


Assuntos
Pan troglodytes/fisiologia , Vocalização Animal , Fatores Etários , Animais , Feminino , Masculino , Predomínio Social , Uganda
10.
Folia Primatol (Basel) ; 90(1): 3-64, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30799412

RESUMO

To improve our understanding of the evolutionary origins of culture and technology in humans, it is vital that we document the full extent of behavioural diversity in our great ape relatives. About half of the world's remaining chimpanzees (Pan spp.) live in the Democratic Republic of Congo (DRC), yet until now we have known almost nothing about their behaviour. Here we describe the insect-related tool technology of Bili-Uéré chimpanzees (Pan troglodytes schweinfurthii) inhabiting an area of at least a 50,000-km2 area in northern DRC, as well as their percussive technology associated with food processing. Over a 12-year period, we documented chimpanzee tools and artefacts at 20 survey areas and gathered data on dung, feeding remains and sleeping nests. We describe a new chimpanzee tool kit: long probes used to harvest epigaeic driver ants (Dorylus spp.), short probes used to extract ponerine ants and the arboreal nests of stingless bees, wands to dip for D. kohli and stout digging sticks used to access underground meliponine bee nests. Epigaeic Dorylus tools were significantly longer than the other tool types, and D. kohli tools were significantly thinner. Tools classified as terrestrial honey-digging sticks were a significant predictor for brushed and blunted tool ends, consistent with their presumed use. We describe two potential new tool types, an "ant scoop" and a "fruit hammer." We document an extensive percussive technology used to process termite mounds of Cubitermes sp. and Thoracotermes macrothorax and hard-shelled fruits such as Strychnos, along with evidence of the pounding open of African giant snails and tortoises. We encountered some geographic variation in behaviour: we found honey-digging tools, long driver ant probes and fruit-pounding sites only to the north of the Uele River; there were more epigaeic Dorylus tools to the north and more ponerine ant tools to the south. We found no evidence of termite-fishing, despite the availability of Macrotermes muelleri mounds throughout the region. This lack of evidence is consistent with the results of dung washes, which revealed a substantial proportion of driver ants, but no evidence of Macrotermes or other termites. Our results allow us to describe a new chimpanzee behavioural complex, characterised by a general similarity of multiple behaviours across a large, ecologically diverse region but with subtle differences in prey choice and techniques. We propose that this widespread and related suite of behaviours be referred to as the Bili-Uéré Chimpanzee Behavioural Realm. Possible explanations for this pattern are a recent chimpanzee expansion across the region and the interconnectedness of this population across at least the entirety of northern DRC.


Assuntos
Comportamento Alimentar , Pan troglodytes/fisiologia , Comportamento de Utilização de Ferramentas , Animais , Formigas , Abelhas , República Democrática do Congo , Feminino , Masculino
11.
Evol Anthropol ; 28(2): 60-71, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30771227

RESUMO

Reconstructing plant use before domestication is challenging due to a lack of evidence. Yet, on the small number of sites with assemblages, the wide range of different plant species cannot be explained simply in terms of nutrition. Assemblages from the Lower Paleolithic to the Early Neolithic were examined to investigate the relative edible and medicinal properties of the plants. The assemblages contain a mixture of edible species, plants that are both edible and medicinal, and plants with only medicinal properties. The proportion of medicinal plants at all sites is well above the natural average and increases over time. Mechanisms for preventing intestinal parasitic infections are common among animals and together with chimpanzees' preventative and curative self-medication practices suggest an evolutionary context for this behavior. A broad-spectrum approach to plant collection is likely to have been in place throughout the Paleolithic driven, in part, by the need for medicinal compounds.


Assuntos
Dieta , Hominidae/fisiologia , Plantas Comestíveis , Plantas Medicinais , Automedicação , Animais , Dieta/história , Dieta/veterinária , Comportamento Alimentar , História Antiga , Humanos , Enteropatias Parasitárias/prevenção & controle , Enteropatias Parasitárias/veterinária , Paleontologia , Pan troglodytes/fisiologia , Automedicação/história , Automedicação/veterinária
12.
Primates ; 60(2): 125-131, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30806863

RESUMO

This study was designed to investigate the foraging behavior of zoo-housed western lowland gorillas (Gorilla gorilla gorilla) and compare it with that of zoo-housed chimpanzees (Pan trogloydytes) tested previously in a similar paradigm. Specifically, we aimed to document how a group of zoo-housed gorillas foraged within a familiar environment to discover novel food sources and whether they sought out more preferred foods, even if they had to travel further to reach them, as they do in the wild. Gorillas were provided plastic tokens to exchange with researchers at two locations-at the same location as the tokens (close) for carrot pieces and another 6.5 m away (far) for grapes. Over the course of 30 sessions, a single individual-the silverback male-accounted for 96% of the 1546 tokens exchanged, all of which took place at the far location. Inter-individual distance measures collected during each session, as well as during matched control sessions, showed that while both gorillas and chimpanzees express similar patterns of social association across the two conditions, the average dyadic association for chimpanzees was stronger than that for gorillas. Together, these findings provide an example of the value of employing identical methodologies to compare cognition and behavior across species as well highlight the importance of the social context in which studies take place.


Assuntos
Comportamento Alimentar , Gorilla gorilla/fisiologia , Pan troglodytes/fisiologia , Comportamento Social , Animais , Animais de Zoológico , Feminino , Masculino
13.
Am J Phys Anthropol ; 168(4): 665-675, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30693959

RESUMO

OBJECTIVES: Food scarcity is proposed to be a limitation to chimpanzees at the limits of their range; however, such a constraint has never been investigated in this context. We investigated patterns of δ13 C and δ15 N variation along a latitudinal gradient at the northwestern West African chimpanzee (Pan troglodytes verus) range limit with the expectation that isotope ratios of chimpanzees at the range limit will indicate different dietary strategies or higher physiological constraints than chimpanzees further from the edge. MATERIALS AND METHODS: We measured δ13 C and δ15 N values in hair (n = 81) and plant food (n = 342) samples from five chimpanzee communities located along a latitudinal gradient in Southeastern Senegal. RESULTS: We found clear grouping patterns in hair δ13 C and δ15 N in the four southern sites compared to the northernmost site. Environmental baseline samples collected from these sites revealed overall higher plant δ15 N values at the northernmost site, but similar δ13 C values across sites. By accounting for environmental baseline, Δ13 C and Δ15 N values were clustered for all five sites relative to total Pan variation, but indicated a 13 C-enriched diet at the range limit. DISCUSSION: Clustering in Δ13 C and Δ15 N values supports that strategic shifting between preferred and fallback foods is a likely ubiquitous but necessary strategy employed by these chimpanzees to cope with their environment, potentially allowing chimpanzees at their limits to avoid periods of starvation. These results also underline the necessity of accounting for local isotopic baseline differences during inter-site comparison.


Assuntos
Isótopos de Carbono/análise , Dieta , Comportamento Alimentar/fisiologia , Isótopos de Nitrogênio/análise , Pan troglodytes/fisiologia , Animais , Antropologia Física , Ecossistema , Metabolismo Energético/fisiologia , Cabelo/química , Plantas Comestíveis/química , Senegal
14.
Anim Cogn ; 22(5): 605-618, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-30338419

RESUMO

A key challenge for primates is coordinating behaviour with conspecifics in large, complex social groups. Gestures play a key role in this process and chimpanzees show considerable flexibility communicating through single gestures, sequences of gestures interspersed with periods of response waiting (persistence), and rapid sequences where gestures are made in quick succession, too rapid for the response waiting to have occurred. The previous studies examined behavioural reactions to single gestures and sequences, but whether this complexity is associated with more complex sociality at the level of the dyad partner and the group as a whole is not well understood. We used social network analysis to examine how the production of single gestures and sequences of gestures was related to the duration of time spent in proximity and individual differences in proximity in wild East African chimpanzees (Pan troglodytes schweinfurthii). Pairs of chimpanzees that spent a longer duration of time in proximity had higher rates of persistence sequences, but not a higher rate of single gestures or rapid sequences. The duration of time spent in proximity was also related to the rate of responding to gestures, and response to gesture by activity change. These results suggest that communicative persistence and the type of response to gestures may play an important role in regulating social interactions in primate societies.


Assuntos
Comunicação Animal , Gestos , Pan troglodytes , Animais , Atenção , Feminino , Individualidade , Masculino , Pan troglodytes/fisiologia , Primatas
15.
Primates ; 60(1): 29-39, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30443802

RESUMO

Using a two-bottle choice test of short duration, we determined taste preference thresholds for sucrose, fructose, glucose, lactose, and maltose in three Western chimpanzees (Pan troglodytes verus). Further, we assessed relative preferences for these five saccharides when presented at equimolar concentrations and determined taste preference difference thresholds for sucrose, that is, the smallest concentration difference at which the chimpanzees display a preference for one of the two options. We found that the chimpanzees significantly preferred concentrations as low as 20 mM sucrose, 40 mM fructose, and 80 mM glucose, lactose, and maltose over tap water. When given a choice between all binary combinations of these five saccharides presented at equimolar concentrations of 100, 200, and 400 mM, respectively, the animals displayed significant preferences for individual saccharides in the following order: sucrose > fructose > glucose = maltose = lactose. The taste difference threshold for sucrose, expressed as Weber ratio (ΔI/I), was 0.3 and 0.4, respectively, at reference concentrations of 100 and 200 mM. The taste sensitivity of the chimpanzees to the five saccharides falls into the same range found in other primate species. Remarkably, their taste preference thresholds are similar, and with two saccharides even identical, to human taste detection thresholds. The pattern of relative taste preferences displayed by the chimpanzees was similar to that found in platyrrhine primates and to the pattern of relative sweetness as reported by humans. Taken together, the results of the present study are in line with the notion that taste sensitivity for food-associated carbohydrates may correlate positively with phylogenetic relatedness. Further, they support the notion that relative preferences for food-associated carbohydrates, but not taste difference thresholds, may correlate with dietary specialization in primates.


Assuntos
Dissacarídeos/fisiologia , Monossacarídeos/fisiologia , Pan troglodytes/fisiologia , Limiar Gustativo , Animais , Animais de Zoológico/fisiologia , Feminino , Masculino , Suécia
16.
Am J Phys Anthropol ; 168(1): 3-9, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30302748

RESUMO

OBJECTIVES: Infanticide by males is common in mammals. According to the sexual selection hypothesis, the risk is inversely related to infant age because the older the infant, the less infanticide can shorten lactational amenorrhea; risk is also predicted to increase when an infanticidal male's chance of siring the replacement infant is high. Infanticide occurs in chimpanzees (Pan troglodytes), a species in which male dominance rank predicts paternity skew. Infanticidal male chimpanzees (if low-ranking) are unlikely to kill their own offspring, whereas those who are currently rising in rank, particularly when this rise is dramatic, have an increased likelihood of fathering potential future infants relative to any existing ones. Given that mothers should behave in ways that reduce infanticide risk, we predicted that female chimpanzees, and specifically those with younger, more vulnerable infants, would attempt to adjust the exposure of their infants to potentially infanticidal males. Specifically, mothers of young infants should reduce their association with adult males in general, and to a greater extent, with both low-ranking males and those rising in rank from a position where paternity of current infants was unlikely, to a rank where the probability of siring the next infant is significantly higher. We also investigated the alternative possibility that rather than avoiding all adult males, mothers would increase association with males of stable high rank on the basis that such males could offer protection against infanticide. MATERIALS AND METHODS: We examined data on female association patterns collected from the Budongo Forest, Uganda, during a period encompassing both relative stability in the male hierarchy and a period of instability with a mid-ranking male rising rapidly in rank. RESULTS: Using linear mixed models, we found that mothers reduced their association with the rank-rising male, contingent on infant age, during the period of instability. We also found evidence that females preferentially associated with a potential protector male during the high-risk period. DISCUSSION: Our results support the sexually selected hypothesis for infanticide and demonstrate that female chimpanzees are sensitive to the relative risks posed by adult males.


Assuntos
Agressão/fisiologia , Comportamento Animal/fisiologia , Pan troglodytes/fisiologia , Animais , Animais Recém-Nascidos , Feminino , Hierarquia Social , Masculino , Mães
17.
J Hum Evol ; 125: 27-37, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30502895

RESUMO

Human bipedalism is characterized by mediolateral oscillations of the center of mass (CoM) between the feet. The preferred step widths and CoM oscillations used by humans likely represent a trade-off of several factors (e.g., stance and swing phase costs). However, it is difficult to assess whether human frontal plane control strategies are unique given few detailed data on frontal plane motion during facultative bipedalism in apes. Here, we collected three-dimensional kinematic and kinetic data in humans and chimpanzees to investigate the relationship between step width, mediolateral CoM motion, frontal plane trunk kinematics, and CoM power during bipedalism. Chimpanzee bipedalism entails mediolateral CoM oscillations and step widths that are (scaled to lower/hind limb length) three times larger than those of humans. Chimpanzees use a combination of linear and angular motion of the trunk and list the entire trunk, and especially thorax, over the stance side foot, generating large mediolateral shifts in the CoM, whereas humans utilize little angular motion within the trunk. Larger mediolateral CoM motions do not have a significant effect on CoM power. Similarities between bipedal chimpanzees and other bipedal non-human primates (macaques and gibbons) indicate that narrow CoM motions are unique to humans and are likely due to our adducted hips and valgus knees. Valgus knees appear early in the human fossil record (∼3.6 Ma), contemporaneous with the Laetoli footprints. However, fossils attributed to Ardipithecus ramidus (∼4.4 Ma) suggest that the earliest hominins may have lacked a hominin-like degree of knee valgus. If correct, this suggests that this species may have used wide steps, larger mediolateral CoM motions, and perhaps larger trunk motions during bipedal walking. Finally, we present a novel means to estimate mediolateral CoM motion from trackway step width, and estimate that the Laetoli G track maker used CoM motions within the human range.


Assuntos
Pan troglodytes/fisiologia , Caminhada , Adulto , Animais , Fenômenos Biomecânicos , Feminino , Marcha , Humanos , Masculino , Adulto Jovem
18.
J Hum Evol ; 125: 99-105, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30502901

RESUMO

Humans differ in many respects from other primates, but perhaps no derived human feature is more striking than our naked skin. Long purported to be adaptive, humans' unique external appearance is characterized by changes in both the patterning of hair follicles and eccrine sweat glands, producing decreased hair cover and increased sweat gland density. Despite the conspicuousness of these features and their potential evolutionary importance, there is a lack of clarity regarding how they evolved within the primate lineage. We thus collected and quantified the density of hair follicles and eccrine sweat glands from five regions of the skin in three species of primates: macaque, chimpanzee and human. Although human hair cover is greatly attenuated relative to that of our close relatives, we find that humans have a chimpanzee-like hair density that is significantly lower than that of macaques. In contrast, eccrine gland density is on average 10-fold higher in humans compared to chimpanzees and macaques, whose density is strikingly similar. Our findings suggest that a decrease in hair density in the ancestors of humans and apes was followed by an increase in eccrine gland density and a reduction in fur cover in humans. This work answers long-standing questions about the traits that make human skin unique and substantiates a model in which the evolution of expanded eccrine gland density was exclusive to the human lineage.


Assuntos
Glândulas Écrinas/fisiologia , Folículo Piloso/fisiologia , Macaca mulatta/fisiologia , Pan troglodytes/fisiologia , Animais , Evolução Biológica , Humanos
19.
Proc Natl Acad Sci U S A ; 115(45): 11393-11400, 2018 11 06.
Artigo em Inglês | MEDLINE | ID: mdl-30397113

RESUMO

Understanding intraspecific variation in sociality is essential for characterizing the flexibility and evolution of social systems, yet its study in nonhuman animals is rare. Here, we investigated whether chimpanzees exhibit population-level differences in sociality that cannot be easily explained by differences in genetics or ecology. We compared social proximity and grooming tendencies across four semiwild populations of chimpanzees living in the same ecological environment over three consecutive years, using both linear mixed models and social network analysis. Results indicated temporally stable, population-level differences in dyadic-level sociality. Moreover, group cohesion measures capturing network characteristics beyond dyadic interactions (clustering, modularity, and social differentiation) showed population-level differences consistent with the dyadic indices. Subsequently, we explored whether the observed intraspecific variation in sociality could be attributed to cultural processes by ruling out alternative sources of variation including the influences of ecology, genetics, and differences in population demographics. We conclude that substantial variation in social behavior exists across neighboring populations of chimpanzees and that this variation is in part shaped by cultural processes.


Assuntos
Comportamento Competitivo/fisiologia , Comportamento Cooperativo , Asseio Animal/fisiologia , Modelos Estatísticos , Pan troglodytes/psicologia , Conformidade Social , Animais , Feminino , Masculino , Pan troglodytes/fisiologia , Dinâmica Populacional , Predomínio Social , Zâmbia
20.
PLoS One ; 13(11): e0207378, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30485317

RESUMO

Primates have evolved to rapidly detect and respond to danger in their environment. However, the mechanisms involved in attending to threatening stimuli are not fully understood. The dot-probe task is one of the most widely used experimental paradigms to investigate these mechanisms in humans. However, to date, few studies have been conducted in non-human primates. The aim of this study was to investigate whether the dot-probe task can measure attentional biases towards threatening faces in chimpanzees. Eight adult chimpanzees participated in a series of touch screen dot-probe tasks. We predicted faster response times towards chimpanzee threatening faces relative to neutral faces and faster response times towards faces of high threat intensity (scream) than low threat intensity (bared teeth). Contrary to prediction, response times for chimpanzee threatening faces relative to neutral faces did not differ. In addition, we found no difference in response times for faces of high and low threat intensity. In conclusion, we found no evidence that the touch screen dot-probe task can measure attentional biases specifically towards threatening faces in our chimpanzees. Methodological limitations of using the task to measure emotional attention in human and non-human primates, including stimulus threat intensity, emotional state, stimulus presentation duration and manual responding are discussed.


Assuntos
Emoções/fisiologia , Face , Pan troglodytes/fisiologia , Resolução de Problemas/fisiologia , Percepção Visual/fisiologia , Animais , Feminino , Humanos , Masculino , Pan troglodytes/psicologia
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