Aaron Sandel

Aaron Sandel
University of Texas at Austin | UT · Department of Anthropology

About

33
Publications
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Introduction

Publications

Publications (33)
Article
How animals grow and when they stop growing are key variables for understanding life history evolution. Although theoretically straightforward, it is logistically difficult to take body size measurements of wild animals, especially endangered and arboreal primates. Here we employ a method that has gained popularity over the past decade: digital pho...
Article
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Caring for others is a key feature of human behavior. Mothers, fathers, siblings, grandparents, and other group members provide care in the form of provisioning, protection, and first aid. To what extent is other-regarding behavior present in our primate relatives? Here we describe an unusual incident of other-regarding behavior toward an injured j...
Article
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Many animals engage in sociosexual behaviour, including that between same-sex pairs. Bonobos ( Pan paniscus ) are famous for their sociosexual behaviour, but chimpanzees ( Pan troglodytes ) apparently do not engage in sociosexual behaviour frequently. However, sociosexual behaviour in chimpanzees may have been overlooked. We observed 584 instances...
Article
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Many animals engage in aggression, but chimpanzees stand out in terms of fatal attacks against adults of their own species. Most lethal aggression occurs between groups, where coalitions of male chimpanzees occasionally kill members of neighboring communities that are strangers. However, the first observed cases of lethal violence in chimpanzees, w...
Article
Like many animals, adult male chimpanzees often compete for a limited number of mates. They fight other males as they strive for status that confers reproductive benefits and use aggression to coerce females to mate with them. Nevertheless, small-bodied, socially immature adolescent male chimpanzees, who cannot compete with older males for status n...
Article
Respiratory pathogens are expected to spread through social contacts, but outbreaks often occur quickly and unpredictably, making it challenging to simultaneously record social contact and disease incidence data, especially in wildlife. Thus, the role of social contacts in the spread of infectious disease is often treated as an assumption in diseas...
Article
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Mothers provide indispensable care for infants in many mammalian species. In some long-lived species, the maternal-offspring bond persists after infancy with mothers continuing to provide resources and social support to their adult progeny. Maternal presence is associated with fitness benefits through adolescence for male chimpanzees despite the fa...
Article
Premasticated food transfer, when an individual partially breaks down food through chewing and feeds it to another individual, usually mouth-to-mouth, is described widely across human cultures. This behavior plays an important role in modern humans’ strategy of complementary feeding, which involves supplementing maternal milk in infant diets with p...
Article
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Socioecological theory predicts that larger groups are able to gain better access to resources because of their numerical advantage in intergroup contests. Nevertheless, the numerical superiority hypothesis has received mixed support, perhaps due to the collective action problem and sex differences in strategies and payoffs. We tested the numerical...
Article
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Social relationships play an important role in animal behavior. Bonds with kin provide indirect fitness benefits, and those with nonkin may furnish direct benefits. Adult male chimpanzees (Pan troglodytes) exhibit social bonds with maternal brothers as well as unrelated adult males, facilitating cooperative behavior, but it is unclear when these bo...
Article
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Quantifying the costs of mating is key for understanding life-history trade-offs. As a reflection of metabolic rate, body temperature is one metric for assaying these costs. However, conventional methods for measuring body temperature are invasive and unsuitable for the study of free-living populations of endangered species, including great apes. A...
Article
In mammalian species where infanticide by males is likely, females exhibit counterstrategies to prevent or mitigate the costs of infanticide. One putative mitigation strategy is the “Bruce effect,” in which pregnant or inseminated females exposed to an unfamiliar male experience pregnancy block or failure. Females then mate with the new male, thus...
Article
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Ecosystem conservation often focuses on protecting wild places, but many remote forests and expansive savannahs have a deep human history of ecosystem management. Here we document grinding stones in the center of a high conservation-value forest, Kibale National Park, Uganda, indicating a historic human presence. Grinding stones were found at a min...
Article
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Conflicts between individuals are common among animals, with power dynamics often biased toward a particular sex. However, individuals across species exert power differently depending on the primary source of that power. Dominance-based power depends on fighting ability (e.g., greater body size) whereas leverage-based power depends on resources tha...
Preprint
Full-text available
Although paternal investment explains the evolution of fatherhood from a functional perspective, its evolutionary origins are unclear. Here we investigate whether a building block for paternal investment, father-offspring discrimination, is present in our closest living relatives, chimpanzees. Adolescent and young adult males (12 - 21 years old) ma...
Thesis
Strong social bonds play an important role in primate behavior. These bonds feature prominently in the lives of adult male chimpanzees (Pan troglodytes). Male chimpanzee friends form coalitions, share food, join each other on territorial border patrols, and help each other as they attempt to rise in the dominance hierarchy. Despite the importance o...
Article
Recent decades have seen rapid development of new analytical methods to investigate patterns of interspecific variation. Yet these cutting-edge statistical analyses often rely on data of questionable origin, varying accuracy, and weak comparability, which seem to have reduced the reproducibility of studies. It is time to improve the transparency of...
Article
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Dominance hierarchies are a prominent feature of the lives of many primate species. These hierarchies have important fitness consequences, as high rank is often positively correlated with reproduction. Although adult male chimpanzees strive for status to gain fitness benefits, the development of dominance relationships is not well understood. While...
Article
Phylogenetic comparative methods have become standard for investigating evolutionary hypotheses, including in studies of human evolution. While these methods account for the non-independence of trait data due to phylogeny, they often fail to consider intraspecific variation, which may lead to biased or erroneous results. We assessed the degree to w...
Article
Dog social behaviour has been well studied, but little is known about affiliative relationships between dogs. We report a yearlong study of dominance and affiliation in 24 dogs at a dog daycare facility and provide additional details on dog relationships through long-term observations of pairs of dogs who lived together in the same household or met...
Article
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We tested five lemur species-ring-tailed lemurs, ruffed lemurs, mongoose lemurs, black lemurs, and Coquerel's sifakas-(N = 52) in an experiment that evaluated skills for inhibitory control in a social context. First, two human experimenters presented identical food rewards; the "generous" experimenter allowed the subject to eat from her hand, where...
Article
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The comparative method is frequently employed to study primate behavior and evolution. The method is used to infer adaptations, and considerable improvements have been made with respect to its implementation. Despite these advances, scant attention has been given to the nature of the data that are used in comparative analyses. This creates a potent...
Article
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Cognition presents evolutionary research with one of its greatest challenges. Cognitive evolution has been explained at the proximate level by shifts in absolute and relative brain volume and at the ultimate level by differences in social and dietary complexity. However, no study has integrated the experimental and phylogenetic approach at the scal...
Article
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Humans are unusual among mammals in appearing hairless. Several hypotheses propose explanations for this phenotype, but few data are available to test these hypotheses. To elucidate the evolutionary history of human "hairlessness," a comparative approach is needed. One previous study on primate hair density concluded that great apes have systematic...
Article
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The social intelligence hypothesis suggests that living in large social networks was the primary selective pressure for the evolution of complex cognition in primates. This hypothesis is supported by comparative studies demonstrating a positive relationship between social group size and relative brain size across primates. However, the relationship...
Data
The procedure for Experiment 1. (MOV)
Data
The procedure for Experiment 2. (M4V)
Data
Supplemental analyses, Table S1, and Figure S1. (DOCX)
Article
Full-text available
Now more than ever animal studies have the potential to test hypotheses regarding how cognition evolves. Comparative psychologists have developed new techniques to probe the cognitive mechanisms underlying animal behavior, and they have become increasingly skillful at adapting methodologies to test multiple species. Meanwhile, evolutionary biologis...
Article
Many haplorhine primates flexibly exploit social cues when competing for food. Whether strepsirrhine primates possess similar abilities is unknown. To explore the phylogenetic origins of such skills among primates, we tested ringtailed lemurs, Lemur catta, for their ability to exploit social cues while competing for food. We found that in two conte...

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