Behavioral Primatology

" Es peligroso mostrarle demasiado al hombre cuánto se asemeja a los animales, sin hacerle ver al mismo tiempo su grandeza ". Pascal.
En verdad el hombre occidental vive como si la muerte no fuese parte de su vida. Crecemos en discursos que engrandecen la naturaleza distintiva del ser humano, y nos posan como los dueños de la naturaleza y para nada parte de ésta. El alejamiento de nuestras raíces atraviesa el sentido de las relaciones creadas entre las personas, las culturas… una división ficticia de la especie que nos pondría en posición de entender de nuestra naturaleza tanto como el pez del agua. No deja de ser el intelecto la horma que nos limita dentro de la inmensidad de la naturaleza de la que formamos parte. Es absolutamente imposible que las lógicas del pensamiento humano enculturizado y sus ideas adultas alcancen a salirse de ellas mismas: al crearse ponen el límite. En un niño podemos verlo: cuanto más intensamente se le inculcan las lógicas de la cultura, más se le constriñe su imaginación. Chapais cuenta con un amplio conocimiento sobre los estudios en primates que, si bien son insuficientes para el desarrollo de sus propuestas, sí invalidan teorías y supuestos precedentes, y obligan a revisar las teorías e hipótesis en torno al parentesco. El hecho de que los datos sean insuficientes, a mí, como lectora, me impiden atreverme a la crítica. La compleja organización social en la que estamos inmersos, creo que es el campo que futuros estudiosos podrán analizar, pero no presentes. No hay antecedentes a las aglomeraciones urbanas recientes, sus productos se difunden a través de prototipos por las televisiones y medios de masas hasta el último rincón del planeta (…)

Reading is one of the best ways that we can obtain new information, often times many of us do not have the time to sit down and read a book, but many of us do have the time to listen. So, considering I am interested in Paleoanthropology, what do I think are some of the best Anthropology audiobooks to listen to (or read) in 2022.

Please check my list out, and let me know what some of your choices are!

This will be made into a page on my website in the next few days, but please enjoy this PDF for the time being.

Multispecies ethnographic projects are venturing "beyond the human," but how far can they go and remain anthropological? The answer depends on whether such projects align with the surge of ethological research on animal cultures. Based on my fieldwork on wild horses in Galicia, Spain, I make a case for an ethologically informed ethnography that extends cultural analysis to other social species. In this project, I used ethological techniques of direct observation but analyzed the results using Erving Goffman's concepts of face, footing, and civil inattention. My analysis inverts Clifford Geertz's classic study of the Balinese cockfight by making horse sociality the center of analysis, rather than regarding these animals as representations of human status concerns.

As members of professional organizations such as American Society of Primatologists (ASP) and the International Primatological Society (IPS), primatologists must adhere to a set of nonhuman primate-focused principles outlined in resolutions and policy statements on, for example, the ethical treatment of nonhuman primates. Those of us that work in the field must also address issues such as the protection of primate health in the wild and the conservation of wild primate populations. Moreover, we increasingly find ourselves in complex situations where we must balance human and nonhuman primate needs and interests. The selection of commentary pieces in this edition of the American Journal of Primatology originated from presentations given in the symposium, Field Primatology of Today: Navigating the Ethical Landscape, held at the 32nd Annual Meeting of the American Society of Primatologists (ASP) in September 2009. The goals of that symposium and these resulting commentary pieces are threefold: (1) to revive a discussion of key contemporary ethical issues faced by field primatologists, (2) to highlight the need for centrally placed ethical considerations in various facets of our professional lives, particularly research and teaching, and (3) to consider what a comprehensive ethical code that addresses all of these issues might look like.

Modern human technological culture depends on social learning. A widespread assumption for chimpanzee tool-use cultures is that they, too, are dependent on social learning. However, we provide evidence to suggest that individual learning, rather than social learning, is the driver behind determining the form of these behaviours within and across individuals. Low-fidelity social learning instead merely facilitates the reinnovation of these behaviours, and thus helps homogenise the behaviour across chimpanzees, creating the population-wide patterns observed in the wild (what here we call ''socially mediated serial reinnovations''). This is the main prediction of the Zone of Latent Solutions (ZLS) hypothesis. This study directly tested the ZLS hypothesis on algae scooping, a wild chimpanzee tool-use behaviour. We provided naïve chimpanzees (n = 14, Mage = 31.33, SD = 10.09) with ecologically relevant materials of the wild behaviour but, crucially, without revealing any information on the behavioural form required to accomplish this task. This study found that naïve chimpanzees expressed the same behavioural form as their wild counterparts, suggesting that, as the ZLS theory predicts, individual learning is the driver behind the frequency of this behavioural form. As more behaviours are being found to be within chimpanzee's ZLS, this hypothesis now provides a parsimonious explanation for chimpanzee tool cultures.

El Alami A., Chait A. (2009). Le singe magot, Macaca sylvanus comme indicateur biologique de la qualité de la forêt marocaine. Colloque hispano-marocain sur la “Gestion des espaces forestiers du nord du Maroc : du protectorat à la réserve de la biosphère”. Faculté des Sciences, Université Abdelmalek Essaâdi, Tétouan. 09-10 Juillet 2009.

Comparative data suggest that various preadaptations to human speech evolved at different times for different functions, especially adaptations to
(a) an aquarboreal lifestyle in Mio-Pliocene hominoids,
(b) a littoral lifestyle in Pleistocene Homo (early-Pleistocene coastal dispersal model), e.g.
(1) descent of the larynx relative to the hyoid bone (Miocene adaptation for loud and varied territorial duets),
(2) descent of the hyoid relative to the palate, smooth and globular tongue, small mouth, parabolic closed tooth-row with incisiform canines, vaulted and smooth palate with reduction of palatal ridges, MYH16 loss and reduced biting-chewing musculature (Pleistocene suction and swallowing of aquatic foods),
(3) voluntary control of breathing musculature (Pleistocene littoral diving during coastal dispersal of Homo),
(4) cerebral expansion (aquatic foods rich in brain-specific nutrients such as DHA, iodine, taurine and oligo-elements),
(5) vocal learning (arguably facilitating localization of offspring).

Dietary preferences of white-faced capuchins monkeys (C. capucinus) in northwestern Costa Rica were examined across age classes and between two distinct seasons over the course of 1 year. The findings show that the dietary profiles of small juveniles, large juveniles, and adults are quite similar, suggesting that juveniles are efficient foragers from a young age. The predictions of several ontogenetic models are presented, and the data lend limited support to the juvenile risk aversion and motor ability models.

Ten researchers collaborated in a long-term study of social conventions in wild white-faced capuchin monkeys, involving examination of a 19,000-hour combined data set collected on 13 social groups at four study sites in Costa Rica over a 13-year period. Five behavior patterns qualified as social traditions, according to the study’s criteria: handsniffing, sucking of body parts, and three types of “games.” Some conventions were independently invented in virtually identical form at multiple sites. The extinction of several conventions was observed during the course of the study; it appears that they rarely last longer than ten years. It is hypothesized that the monkeys are using these group- or clique-specific social conventions to test the quality of their social relationships.

Ideas about nonhuman primates have long been used to talk about human gender and aggression.  Due to phylogenetic relatedness and popular conceptions of similarities, behavioral studies of nonhuman primates have a much greater impact on ideas about human behavior than studies of other groups of organisms.  Because of our biological basis for shared traits resulting from a common evolutionary heritage, nonhuman primate behavior is often put forward as evidence of an underlying natural condition or of normative roles in human behavior. In recent years, the evidence for the diversity and complexity of nonhuman primate behavior has complicated the process of generalizing from primate to human behavior.  Yet, at the same time, certain reductionist accounts--stemming primarily from sociobiology and evolutionary psychology--have have found their way into popularized narratives that rely on analogies between primate and human behavior that have little basis in the evidence of primatology.  This chapter focuses on the tension between these two trends in the uses of primatology, particularly as they relate to discussions of male aggression and male dominance.

Discoverers of the hominid naledi fossils (300-250 ka, Gauteng, southern Africa, first described in 2015) anthropocentrically assume that naledi (1) belonged to the genus Homo, (2) buried their dead in caves, (3) were tool makers, (4) ran over African plains. Comparative anatomy shows these assumptions to be wrong, and suggests that naledi (1) generally resembled bonobos and belonged to the genus Pan or Australopithecus, (2) fossilized in a natural way, (3) were no better tool makers than extant chimpanzees are, (4) spent an important part of their day wading bipedally in forest swamps or wetlands, in search for wetland foods, possibly waterlilies or other aquatic herbaceous vegetation (AHV, possibly containing small snails), like bonobos and lowland gorillas still do but more frequently.

Male chimpanzees, Pan troglodytes, defend group territories, and sometimes injure or kill members of other groups. To test which factors best predict the occurrence and outcomes of intergroup encounters, we analysed 15 years of data on intergroup encounters, party composition, ranging and feeding behaviour in the Kanyawara community of chimpanzees, Kibale National Park, Uganda. During this time, researchers observed 120 intergroup encounters, most of which (85%) involved only acoustic contact. The majority of encounters (63%) occurred in the southeast quadrant of the range. Multiple logistic regression found that intergroup encounters occurred more often when chimpanzees were far from the centre of their range, especially in the south, and when eating foods that were most abundant in the south. Multiple linear regression found that chimpanzees travelled further from the centre of their range, and further south, when eating a few key foods, especially fruits of Uvariopsis congensis, and when in parties with more males. Upon hearing calls from foreign chimpanzees, Kanyawara chimpanzees were more likely to vocalize in response, and to travel towards the foreign chimpanzees, when they had more males in their party. Measures of two resource values, food and mates, were negatively correlated with the probability of vocalizing and approaching intruders, respectively. These findings indicate that, in this population, resources affect the timing of intergroup encounters, but the decision to escalate a contest depends mainly on numerical strength, rather than the value of resources being contested.

O emprego da violência interpessoal tem destaque no conjunto de instrumentos comportamentais de uma ampla gama de espécies que habitam ou habitaram o Planeta, e é algo que representa um diferencial evolucionário na competição individual pelas fontes de subsistência e no sucesso reprodutivo, em determinadas circunstâncias ecológicas. O consistente desenvolvimento da vida social, em curso desde a adoção de hábitos diurnos há 52 Ma, e amplamente potencializado com a formação de pares ou de haréns a partir de algumas espécies da família Hominidae por volta de 16-12 Ma, além de funcionar, ele próprio, como uma inovação comportamental adaptativa, gerou um contexto complexo que levaria o exercício da violência e do poder a ganhar novas dimensões, milhões de anos depois. Em âmbito interno aos grupos sociais, o exercício da força associar-se-ia a estratégias sociais envolvendo intricadas ritualizações e o sutil emprego de estratagemas e subterfúgios, incluindo nas ferinas disputas por status a formação de alianças em torno de objetivos comuns. No âmbito externo, a projeção de poder também viria a superar a antediluviana tendência, frequente nos mamíferos, às disputas entre indivíduos, dando origem à novidade evolucionária consubstanciada no fenômeno da violência coalizacional. Surgiam, então, genuínas relações sociais de poder que ultrapassavam, embora incorporassem, a mera instância interpessoal, assumindo uma dimensão coletiva e intersocietária. É nesse sentido que a intensa sociabilidade demonstrada pelos grandes primatas antropoides estantes – excetuando os orangotangos, do gênero Pongo – sugere um interessante emaranhamento entre o social e a dinâmica evolutiva, entre a vida coletiva, com sua lógica de cooperação e conflito intra e intergrupal, e aquele domínio vitorianamente consagrado ao indivíduo (a origem e evolução das espécies). E de forma mais específica, são traços compartilhados entre P. troglodytes e H. sapiens – os chimpanzés comuns e os humanos modernos –, adequados integralmente ao portfólio comportamental descrito, que nos fazem imaginar que tanto a violência coalizacional quanto a projeção de poder interssocietária possam se configurar como uma condição sinapomórfica  , desenvolvida e transmitida no decurso evolucionário de algumas espécies da subfamília Homininae, com laços filogenéticos entre si, e que remetem pelo menos ao último ancestral comum (UAC) entre os gêneros Pan e Homo.
Assim, o desenvolvimento da violência coalizacional e da projeção de poder interssocietária teria percorrido uma senda evolucionária de ao menos seis milhões de anos, gerando uma identidade elusiva entre os reides promovidos por bandos de chimpanzés contra grupos vizinhos rivais nas florestas equatoriais da África Central, os massacres que marcaram a vivência social de H. sapiens durante a Última Era Glacial, e os dantescos choques entre sociedades organizadas em Estados, no curtíssimo intervalo entre o surgimento da agricultura, há aproximadamente dez mil anos, e os tempos atuais. Esse fenômeno de longuíssima duração, a filogenia da guerra, superaria absolutamente a percepção subjetiva de seus agentes históricos (fosse pela sua própria condição, fosse pela ausência de instrumentos cognitivos para o conceito de temporalidade), e, operando num pano de fundo inconsciente, estrutural, tensionaria e problematizaria dialeticamente cada episódio envolvendo o poder e a guerra em temporalidades mais curtas, sem determiná-los.

Unrelated male primates frequently cohabit in bisexual groups and, despite being reproductive competitors, have been shown to cooperate in ways that are associated with reproductive success. Such coalitions between males are common in some taxa, where they can serve two primary functions – status management and improved mating opportunities– that subserve long- and short-term objectives. Here, we use
observational data to provide information on male coalitions in vervet monkeys (Chlorocebus pygerythrus), a guenon with a multimale group structure. We recorded a total of 62 coalitions from two troops across a 10-mo period at Samara Game Reserve, South Africa. We found that males who were more frequently associated spatially and who had groomed one another were more likely to form coalitions and did so
against higher-ranking opponents. This was not linked to any evidence that coalitionary aggression provided either short- or long-term reproductive benefits for the aggressors and coalitions were not restricted to the mating season. There was little evidence that particular individuals were targeted, reciprocation between partners was not observed, and
recent immigrant males were not targeted disproportionately. Our data suggest that within-group coalition formation between vervet males may represent something close to an ancestral state whereby males form ad hoc coalitions opportunistically, joining an ongoing dyadic contest to target an opponent without facing the possible risks of dyadic contest, such as a greater chance of injury.

Stress has been a subject of intense research over the past few decades. Any holistic understanding of stress requires an interdisciplinary approach. In particular, psychosocial stress studies must include both sociocultural and biochemical variables in their design. In this experiment, the author used a competitive binding immunoassay to quantify cortisol samples before and after an exam in undergraduate university students (n = 29). Multiple variables potentially relating to cortisol production and psychosocial stress reactions were assessed using a pre-exam questionnaire. This questionnaire also included a question regarding perceived preparedness before and after the exam. It was hypothesized that a rise in cortisol (signifying a stress response) would correlate with negative change between predicted preparedness for an exam and retrospect preparedness. Out of 29 students, 10 exhibited a rise in cortisol. Of those 10, 9 noted a decrease in confidence after the exam. A contingency table was used to organize data for a Chi2 analysis. It was found that a rise in cortisol was significantly correlated with a negative change in confidence (p < 0.05). Future studies should investigate the roles of corticosteroid binding globulin and other possible variables in salivary cortisol measurement as well as any effects of group study on pre-exam salivary cortisol levels.

“Humans can see the world around them, imagine how it might be different, and translate those imaginings into reality…or at least try to. Humans believe. Meaning, imagination, and hope are as central to the human story as are bones, genes, and ecologies. Neither selfish aggression nor peaceful altruism dominates human behavior as a whole. We are a species distinguished by our extraordinary capacity for creative cooperation, our ability to imagine possibilities and to make them material, and our powerful aptitudes for belief, hope, and cruelty.” So begins the abstract for Agustín Fuentes’ 2018 Gifford Lecture series at the University of Edinburgh on the topic “Why We Believe: evolution, making meaning, and the development of human natures.”

In this wide-ranging interview, Chris and Professor Fuentes discuss the themes of the lecture series, the intersections of research on human evolution, ethnoprimatology, and human nature, with the study of religion more generally, the Planet of the Apes films, and more. Along the way, important distinctions are made between specific “beliefs”, “belief systems” and the human “capacity to believe”, and we ask some important questions about the future.

It is widely believed that there is strong association between physiological stress and an individual's social status in their social hierarchy. This has been claimed for all humans cross-culturally, as well as in non-human animals living in social groups. However, the relationship between stress and social status has not been explored in any egalitarian hunter-gatherer society; it is also under investigated in exclusively female social groups. Most of human evolutionary history was spent in small, mobile foraging bands of hunter-gatherers with little economic differentiation-egalitarian societies. We analysed women's hair cortisol concentration along with two domains of women's social status (foraging reputation and popularity) in an egalitarian hunter-gatherer society, the Hadza. We hypothesized that higher social status would be associated with lower physiological indicators of stress in these women. Surprisingly, we did not find any association between either foraging reputation or popularity and hair cortisol concentration. The results of our study suggest that social status is not a consistent or powerful predictor of physiological stress levels in women in an egalitarian social structure. This challenges the notion that social status has the same basic physiological implications across all demographics and in all human societies.

Fundamental reproductive interests dictate that females generally benefit most from mate selectivity and males from mate quantity.  This can create conflict between the sexes and result in sexual coercion: male use of aggression to garner mating success at a cost to females.  Potential fitness costs of sexual coercion, however, can be difficult to measure.  Here we demonstrate benefits to males and costs to females of female defense polygyny in wild hamadryas baboons, cercopithecoid primates in which females are coercively transferred among social units by males, restricting both female choice and bonding among female kin. Of all coercive transfers (takeovers) of females with young infants, 67% were followed by infant mortality, which was significantly more likely to occur after takeovers than at other times.  As expected, infant mortality decreased time to subsequent conception but lengthened intervals between surviving infants.  Following infant survival, whether a female had experienced a takeover after the previous birth was a significant predictor of subsequent interbirth interval, with interbirth intervals of females remaining with the same male between births being significantly shorter than those of females incurring takeovers between births.  Together these results reveal that takeovers increase the chance of infant mortality while delaying subsequent conception.  Male-driven female defense polygyny in this species is thus costly to females in two ways.  These results demonstrate that reproductive strategies benefitting males can evolve despite substantial costs to females.  These costs may be mitigated over the long term, however, by female counterstrategies and protective behavior by males.

Our results demonstrate that very simple objects for environmental enrichment can initiate more types of behaviour in the group of gorillas or provoke the new or innovative behavioural patterns. There are three types of objects: plastic boxes and wooden baskets; wooden shaving; long tools, branches and toys. We observed the group of gorillas in Prague Zoo (2009-2018). All animals use these three types of objects daily and include them in the different types of behaviour (play, agonistic, sexual, social, comfort). Boxes and baskets used as a step-stools or seats, weapons, drums as drummers and for the increase effects during chest beating, for the sweeping garbage. Baskets are used for hiding. Wooden shaving used as a pads, making of a primitive slippers (and all youngsters learn this behaviour from their mother), as a neck protectors, as a cushion, use to a clean of the body, creating "Islands" during traveling through the new substrate place. Blocking the photocell on drinking by the wooden shaving enable the use water all the time. After making of primitive slippers gorillas used them for the moving on the wet or cold floor. Our study proves that gorillas are able sophisticated tool behaviour. They do not show much tool modifications, however, the degree in using innovations and active tool using is relatively very high. Some features of their tool activities indicate the origin of traditions, like using of plastic boxes or wooden-shaving slippers. These results show that environmental enrichment could reveal mechanisms of formation of early hominine tool behaviour and relations of using tools to the development of early hominine cognitive abilities.

Macaca sinica is the smallest of all 22 extant macaque species in the world. There are three geographically isolated endemic sub-species of M. sinica: M. s. sinica, M. s. aurifrons and M. s. opisthomelas in Sri Lanka. Macaques adjust their activities to deal with changeable environments like weather changes and food availability fluctuations, proving their plasticity nature. Current study focused on assessing the temporal variation of activity budgets and effects of temperature on their activity pattern. Behavioral data were collected using scan sampling method. Overall activity budget analysis found that they allocate more time on resting (32.60 ± 4.97%), whereas less time spent for moving (26.30 ± 3.15%) and feeding (19.60 ± 2.97%). Moving was negatively correlated with monthly average temperature (r=-0.489 p= 0.029). The study found that time allocation for moving was reduced to compensate their thermoregulatory cost in terms of energy. This suggests that changes in movements of M. s. aurifrons are a useful indicator in assessing environmental changes such as temperature alterations.

Small-scaled variability in a mosaic tropical rainforest influenced habitat use of longtailed
Macaques
Sha, J.C.M., Chua, S.C., Chew, P.T. et al. Primates (2017). https://doi.org/10.1007/s10329-017-0630-y

Corresponding Author
Zhang Peng
Email: zhangp99@mail.sysu.edu.cn
https://link.springer.com/article/10.1007/s10329-017-0630-y
Abstract:  Pristine habitats have generally been expounded to be the most important ecological resources for wildlife conservation, but due to forest degradation caused by human activities, mosaics of secondary forests have become increasingly prominent. We studied three forest types in a mosaic tropical forest consisting of short secondary forest (SS), tall secondary forest (TS) and freshwater swamp forest (SF). These forests differed in stand structure and floristic composition; as well as phenological productivity of fruits, flowers and young leaves. We examined habitat use of long-tailed macaques (M. fascicularis) in relation to indices of phenological activity. The macaques used the SS for feeding/foraging more than the TS and the SF. This was because the SS had higher productivity of fruits which is a preferred food resource for macaques. Stem densities of young leaves in the SS and the TS also influenced habitat use, as they provided more clumped resources. Use of SF was limited but these forests provided more species rich resources. Our results showed that M. fascicularis responded to small-scaled variability in phenological activity between forest types found in a heterogeneous mosaic forest; with young secondary regrowth forests likely providing the most important food resources. Mosaic landscapes may also be important for other mammalian herbivores as they can buffer the effects of temporal food resource variability in any given forest type. In our increasingly human-altered landscapes, a better understanding of the role of secondary forest mosaics is crucial to the conservation and management of wildlife habitats and the animals they support.
Key words: floristic composition; phenology; stand structure; secondary forest;
摘要： 虽然原始生境被普遍认为是保护野生动物最重要的生态资源，但由于人类活动造成的森林退化，次生林的马赛克化破碎现象日益突出。我们研究比较了食蟹猴对三种的热带森林类型的生境利用，即矮林型次生林（SS）、高林型次生林（TS）和沼泽森林型（SF）。这些森林的林分结构和区系组成不同，而且果实、花朵和嫩叶的物候生产力也不同。我们分析了习惯化食蟹猴群的栖息地利用与物候指数关系。食蟹猴更倾向于在矮林型次生林取食。这可能因为矮林型次生林具有较高的果实产量，这些是猕猴的首选食物来源。矮林型次生林和高林型次生林内嫩叶也是是猕猴较集中的食物来源，嫩叶密度也明显影响猴群的栖息地利用。虽然沼泽森林型有更多的物种丰富度，但是猴群较少使用该类型森林。我们的研究结果表明，食蟹猴对不同类型的破碎化森林有着不同的适应。新形成的次生林可能为猴群提供了最重要的食物资源。实际上，破碎的森林景观对其他的草食性哺乳动物也很重要，因为它们可以缓冲任何既定类型森林内的食物资源短缺等变化对动物的影响。尤其在人类影响日益严重的森林景观中，进一步了解破碎化次生林对于野生动物保护和管理工作具有至关重要的意义。
关键词： 植物区系组成；物候学；林分结构；次生林

Primate life histories are marked by remarkably long prereproductive periods, particularly in atelins. Woolly monkeys have among the longest immature phases relative to their body size, but the behavior of woolly monkey juveniles and adolescents has until now been largely unknown. This chapter establishes guide- lines for identifying developmental landmarks in immature woolly monkeys and presents data on a study of the behavioral development and life history of wild juve- nile and adolescent lowland woolly monkeys ( Lagothrix poeppigii) in Amazonian Ecuador. Despite overall low levels of sociality across all ages in this taxon, some sex-specific developmental patterns emerged. Male immatures preferentially inter- acted with adult male groupmates, presumably to gain access to important social resources. Female immatures appeared to increasingly distance themselves from groupmates up to dispersal, but showed a sharp increase in sexual interest in coresi- dent adult males immediately prior to dispersing. Although data on adolescents are limited, this phase in particular appears to be a time of critical importance to woolly monkey life histories in both males and females, and may be of particular interest for future research.

Researchers have identified a variety of cross-site differences in the foraging behavior of free-ranging great apes, most notably among chimpanzees (Pan troglodytes) and more recently orangutans (Pongo pygmaeus), that are not due to obvious genetic or ecological differences. These differences are often referred to as “traditions.” What is not known is whether this high level of interpopulation variation in behavior is limited to hominoids. In this study, we use long-term data from three Costa Rican field sites that are geographically close and similar ecologically to identify potential foraging traditions in white-faced capuchins (Cebus capucinus). Foraging traditions are predicted in Cebus because of many behavioral and morphological convergences between this genus and the great apes. The processing techniques used for the same food species were compared across sites, and all differences found were classified as present, habitual, or customary. Proximity data were also analyzed to determine if social learning mechanisms could explain variation in foraging behavior. Of the 61 foods compared, we found that 20 of them are processed differently by capuchins across sites. The differences involve pound, rub, tap, “fulcrum,” “leaf-wrap,” and “army ant following.” For most of the differences with enough data to analyze, the average proximity score of the “matched” dyads (two individuals within a group who shared a “different” processing technique) was statistically higher than the average proximity score of the remaining “unmatched” dyads.

Humans live in modular societies with a minimum of two levels of organization, the conjugal family and the local community. Yet any human community is likely to contain at least one other social unit whose evolutionary significance has not always been recognized: a same-sex association, such as a men’s “club” or “brotherhood.” The purpose of this article is to explore the role of all-male associations in relation to the conjugal families that are often taken to be the main constituents of human groups. What has been called bachelor threat in other mammalian species is a major problem in human societies, which may include follower males as well as all-male units. Yet tensions between married men and bachelors are often eclipsed by the need for warriors to defend the local community. The ethnographic record includes many cases in which fraternal security takes precedence over conjugal bonds, resulting in the physical segregation of the sexes, including husbands and wives. At the extreme, a husband usually sleeps at a men’s house while making regular visits to his conjugal family. Though this pattern is classically associated with tribal Amazonia and Melanesia, it is seen here as part of a continuum of variation in small-scale societies worldwide. These societies reflect a series of historical compromises, it is argued, between bachelors and elders, on the one hand, and between men’s associations and conjugal families, on the other.