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Sandel AA. Male-male relationships in chimpanzees and the evolution of human pair bonds. Evol Anthropol 2023; 32:185-194. [PMID: 37269494 DOI: 10.1002/evan.21986] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Revised: 12/27/2022] [Accepted: 05/12/2023] [Indexed: 06/05/2023]
Abstract
The evolution of monogamy has been a central question in biological anthropology. An important avenue of research has been comparisons across "socially monogamous" mammals, but such comparisons are inappropriate for understanding human behavior because humans are not "pair living" and are only sometimes "monogamous." It is the "pair bond" between reproductive partners that is characteristic of humans and has been considered unique to our lineage. I argue that pair bonds have been overlooked in one of our closest living relatives, chimpanzees. These pair bonds are not between mates but between male "friends" who exhibit enduring and emotional social bonds. The presence of such bonds in male-male chimpanzees raises the possibility that pair bonds emerged earlier in our evolutionary history. I suggest pair bonds first arose as "friendships" and only later, in the human lineage, were present between mates. The mechanisms for these bonds were co-opted for male-female bonds in humans.
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Affiliation(s)
- Aaron A Sandel
- Department of Anthropology, University of Texas at Austin, Austin, Texas, USA
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Tkaczynski PJ, Mafessoni F, Girard-Buttoz C, Samuni L, Ackermann CY, Fedurek P, Gomes C, Hobaiter C, Löhrich T, Manin V, Preis A, Valé PD, Wessling EG, Wittiger L, Zommers Z, Zuberbuehler K, Vigilant L, Deschner T, Wittig RM, Crockford C. Shared community effects and the non-genetic maternal environment shape cortisol levels in wild chimpanzees. Commun Biol 2023; 6:565. [PMID: 37237178 DOI: 10.1038/s42003-023-04909-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2022] [Accepted: 05/03/2023] [Indexed: 05/28/2023] Open
Abstract
Mechanisms of inheritance remain poorly defined for many fitness-mediating traits, especially in long-lived animals with protracted development. Using 6,123 urinary samples from 170 wild chimpanzees, we examined the contributions of genetics, non-genetic maternal effects, and shared community effects on variation in cortisol levels, an established predictor of survival in long-lived primates. Despite evidence for consistent individual variation in cortisol levels across years, between-group effects were more influential and made an overwhelming contribution to variation in this trait. Focusing on within-group variation, non-genetic maternal effects accounted for 8% of the individual differences in average cortisol levels, significantly more than that attributable to genetic factors, which was indistinguishable from zero. These maternal effects are consistent with a primary role of a shared environment in shaping physiology. For chimpanzees, and perhaps other species with long life histories, community and maternal effects appear more relevant than genetic inheritance in shaping key physiological traits.
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Affiliation(s)
- Patrick J Tkaczynski
- Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.
- Taï Chimpanzee Project, Centre Suisse de Recherches Scientifiques, Abidjan, Côte d'Ivoire.
- School of Biological and Environmental Sciences, Liverpool John Moores University, Liverpool, UK.
| | - Fabrizio Mafessoni
- Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany.
- Weizmann Institute of Science, Department of Plant and Environmental Sciences, Rehovot, Israel.
| | - Cédric Girard-Buttoz
- Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
- Taï Chimpanzee Project, Centre Suisse de Recherches Scientifiques, Abidjan, Côte d'Ivoire
- The Ape Social Mind Lab, Institut des Sciences Cognitives, CNRS UMR 5229, Lyon, France
| | - Liran Samuni
- Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
- Taï Chimpanzee Project, Centre Suisse de Recherches Scientifiques, Abidjan, Côte d'Ivoire
- Department of Human Evolutionary Biology, Harvard University, Cambridge, MA, USA
- Centre for Social Learning & Cognitive Evolution, School of Psychology & Neuroscience, University of St Andrews, St Andrews, UK
| | - Corinne Y Ackermann
- Universite de Neuchatel, Institut de Biologie, Cognition Compare, Neuchatel, Switzerland
| | - Pawel Fedurek
- Division of Psychology, University of Stirling, Stirling, UK
| | - Cristina Gomes
- Tropical Conservation Institute, Institute of Environment, College of Arts, Science and Education, Florida International University, Miami, FL, USA
| | - Catherine Hobaiter
- Centre for Social Learning & Cognitive Evolution, School of Psychology & Neuroscience, University of St Andrews, St Andrews, UK
| | - Therese Löhrich
- World Wide Fund for Nature, Dzanga Sangha Protected Areas, BP 1053, Bangui, Central African Republic
- Robert Koch Institute, Epidemiology of Highly Pathogenic Microorganisms, Berlin, Germany
| | - Virgile Manin
- Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
- Taï Chimpanzee Project, Centre Suisse de Recherches Scientifiques, Abidjan, Côte d'Ivoire
| | - Anna Preis
- Taï Chimpanzee Project, Centre Suisse de Recherches Scientifiques, Abidjan, Côte d'Ivoire
| | - Prince D Valé
- Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
- Taï Chimpanzee Project, Centre Suisse de Recherches Scientifiques, Abidjan, Côte d'Ivoire
- Unité de Formation et de Recherche Agroferesterie, Université Jean Lorougnon Guédé, Daloa, Côte d'Ivoire
| | - Erin G Wessling
- Department of Human Evolutionary Biology, Harvard University, Cambridge, MA, USA
| | | | - Zinta Zommers
- Perry World House, University of Pennsylvania, Philadelphia, USA
| | - Klaus Zuberbuehler
- Universite de Neuchatel, Institut de Biologie, Cognition Compare, Neuchatel, Switzerland
| | - Linda Vigilant
- Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - Tobias Deschner
- Institute of Cognitive Science, Comparative BioCognition, University of Osnabrück, Osnabrück, Germany
| | - Roman M Wittig
- Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
- Taï Chimpanzee Project, Centre Suisse de Recherches Scientifiques, Abidjan, Côte d'Ivoire
- The Ape Social Mind Lab, Institut des Sciences Cognitives, CNRS UMR 5229, Lyon, France
| | - Catherine Crockford
- Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
- Taï Chimpanzee Project, Centre Suisse de Recherches Scientifiques, Abidjan, Côte d'Ivoire
- The Ape Social Mind Lab, Institut des Sciences Cognitives, CNRS UMR 5229, Lyon, France
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Sandel AA, Negrey JD, Arponen M, Clark IR, Clift JB, Reddy RB, Ivaska KK. The evolution of the adolescent growth spurt: Urinary biomarkers of bone turnover in wild chimpanzees (Pan troglodytes). J Hum Evol 2023; 177:103341. [PMID: 36905703 DOI: 10.1016/j.jhevol.2023.103341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Revised: 02/01/2023] [Accepted: 02/01/2023] [Indexed: 03/11/2023]
Abstract
Life history theory addresses how organisms balance development and reproduction. Mammals usually invest considerable energy into growth in infancy, and they do so incrementally less until reaching adult body size, when they shift energy to reproduction. Humans are unusual in having a long adolescence when energy is invested in both reproduction and growth, including rapid skeletal growth around puberty. Although many primates, especially in captivity, experience accelerated growth in mass around puberty, it remains unclear whether this represents skeletal growth. Without data on skeletal growth in nonhuman primates, anthropologists have often assumed the adolescent growth spurt is uniquely human, and hypotheses for its evolution have focused on other uniquely human traits. The lack of data is largely due to methodological difficulties of assessing skeletal growth in wild primates. Here, we use two urinary markers of bone turnover-osteocalcin and collagen-to study skeletal growth in a large, cross-sectional sample of wild chimpanzees (Pan troglodytes) at Ngogo, Kibale National Park, Uganda. For both bone turnover markers, we found a nonlinear effect of age, which was largely driven by males. For male chimpanzees, values for osteocalcin and collagen peaked at age 9.4 years and 10.8 years, respectively, which corresponds to early and middle adolescence. Notably, collagen values increased from 4.5 to 9 years, suggesting faster growth during early adolescence compared to late infancy. Biomarker levels plateaued at 20 years in both sexes, suggesting skeletal growth continues until then. Additional data, notably on females and infants of both sexes, are needed, as are longitudinal samples. However, our cross-sectional analysis suggests an adolescent growth spurt in the skeleton of chimpanzees, especially for males. Biologists should avoid claiming that the adolescent growth spurt is uniquely human, and hypotheses for the patterns of human growth should consider variation in our primate relatives.
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Affiliation(s)
- Aaron A Sandel
- Department of Anthropology, University of Texas at Austin, WCP 4.102, 2201 Speedway Stop C3200, Austin, TX 78712, USA; Primate Ethology and Endocrinology Lab, University of Texas at Austin, 2201 Speedway Stop C3200, Austin, TX 78712, USA.
| | - Jacob D Negrey
- School of Human Evolution and Social Change, Arizona State University, 900 S. Cady Mall, Tempe, AZ 85281, USA; Department of Pathology/Section on Comparative Medicine, Wake Forest School of Medicine, Winston-Salem, NC 27101, USA
| | - Milja Arponen
- Institute of Biomedicine, University of Turku, Kiinamyllynkatu 10, 20520 Turku, Finland
| | - Isabelle R Clark
- Department of Anthropology, University of Texas at Austin, WCP 4.102, 2201 Speedway Stop C3200, Austin, TX 78712, USA; Primate Ethology and Endocrinology Lab, University of Texas at Austin, 2201 Speedway Stop C3200, Austin, TX 78712, USA
| | - Jeremy B Clift
- Department of Psychological Science, University of Arkansas, 216 Memorial Hall, Fayetteville, AR 72701, USA
| | - Rachna B Reddy
- Department of Human Evolutionary Biology, Harvard University, 11 Divinity Ave, Cambridge, MA 02138, USA; Department of Psychology, Harvard University, 33 Kirkland St, Cambridge, MA 02138, USA; Department of Evolutionary Anthropology, Duke University, 104 Biological Sciences, Durham, NC 27708, USA
| | - Kaisa K Ivaska
- Institute of Biomedicine, University of Turku, Kiinamyllynkatu 10, 20520 Turku, Finland
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Puberty initiates a unique stage of social learning and development prior to adulthood: Insights from studies of adolescence in wild chimpanzees. Dev Cogn Neurosci 2022; 58:101176. [PMID: 36427434 PMCID: PMC9699942 DOI: 10.1016/j.dcn.2022.101176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Revised: 10/28/2022] [Accepted: 11/15/2022] [Indexed: 11/18/2022] Open
Abstract
In humans, puberty initiates a period of rapid growth, change, and formative neurobehavioral development. Brain and behavior changes during this maturational window contribute to opportunities for social learning. Here we provide new insights into adolescence as a unique period of social learning and development by describing field studies of our closest living relatives, chimpanzees. Like humans, chimpanzees have a multiyear juvenile life stage between weaning and puberty onset followed by a multiyear adolescent life stage after pubertal onset but prior to socially-recognized adulthood. As they develop increasing autonomy from caregivers, adolescent chimpanzees explore and develop many different types of social relationships with a wide range of individuals in a highly flexible social environment. We describe how adolescent social motivations and experiences differ from those of juveniles and adults and expose adolescents to high levels of uncertainty, risk, and vulnerability, as well as opportunities for adaptive social learning. We discuss how these adolescent learning experiences may be shaped by early life and in turn shape varied adult social outcomes. We outline how future chimpanzee field research can contribute in new ways to a more integrative interdisciplinary understanding of adolescence as a developmental window of adaptive social learning and resilience.
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Thermal imaging reveals audience-dependent effects during cooperation and competition in wild chimpanzees. Sci Rep 2022; 12:2972. [PMID: 35194084 PMCID: PMC8863809 DOI: 10.1038/s41598-022-07003-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Accepted: 02/09/2022] [Indexed: 12/28/2022] Open
Abstract
Accessing animal minds has remained a challenge since the beginnings of modern science. Here, we used a little-tried method, functional infrared thermal imaging, with wild chimpanzees during common social interactions. After removing confounds, we found that chimpanzees involved in competitive events had lower nose skin temperatures whereas those involved in cooperative events had higher temperatures, the latter more so in high- than low-ranking males. Temperatures associated with grooming were akin to those of cooperative events, except when males interacted with a non-reciprocating alpha male. In addition, we found multiple audience effects. Notably, the alpha male's presence reduced positive effects associated with cooperation, whereas female presence buffered negative effects associated with competition. Copulation was perceived as competitive, especially during furtive mating when other males were absent. Overall, patterns suggest that chimpanzees categorise ordinary social events as cooperative or competitive and that these perceptions are moderated by specific audiences.
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Girard-Buttoz C, Tkaczynski PJ, Samuni L, Fedurek P, Gomes C, Löhrich T, Manin V, Preis A, Valé PF, Deschner T, Wittig RM, Crockford C. Early maternal loss leads to short- but not long-term effects on diurnal cortisol slopes in wild chimpanzees. eLife 2021; 10:e64134. [PMID: 34133269 PMCID: PMC8208813 DOI: 10.7554/elife.64134] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Accepted: 05/19/2021] [Indexed: 12/18/2022] Open
Abstract
The biological embedding model (BEM) suggests that fitness costs of maternal loss arise when early-life experience embeds long-term alterations to hypothalamic-pituitary-adrenal (HPA) axis activity. Alternatively, the adaptive calibration model (ACM) regards physiological changes during ontogeny as short-term adaptations. Both models have been tested in humans but rarely in wild, long-lived animals. We assessed whether, as in humans, maternal loss had short- and long-term impacts on orphan wild chimpanzee urinary cortisol levels and diurnal urinary cortisol slopes, both indicative of HPA axis functioning. Immature chimpanzees recently orphaned and/or orphaned early in life had diurnal cortisol slopes reflecting heightened activation of the HPA axis. However, these effects appeared short-term, with no consistent differences between orphan and non-orphan cortisol profiles in mature males, suggesting stronger support for the ACM than the BEM in wild chimpanzees. Compensatory mechanisms, such as adoption, may buffer against certain physiological effects of maternal loss in this species.
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Affiliation(s)
- Cédric Girard-Buttoz
- Department of Human Behavior, Ecology and Culture, Max Planck Institute for Evolutionary AnthropologyLeipzigGermany
- Taï Chimpanzee Project, Centre Suisse de Recherches ScientifiquesAbidjanCôte d'Ivoire
| | - Patrick J Tkaczynski
- Department of Human Behavior, Ecology and Culture, Max Planck Institute for Evolutionary AnthropologyLeipzigGermany
- Taï Chimpanzee Project, Centre Suisse de Recherches ScientifiquesAbidjanCôte d'Ivoire
| | - Liran Samuni
- Taï Chimpanzee Project, Centre Suisse de Recherches ScientifiquesAbidjanCôte d'Ivoire
- Department of Primatology, Max Planck Institute for Evolutionary AnthropologyLeipzigGermany
- Department of Human Evolutionary Biology, Harvard UniversityCambridgeUnited States
| | - Pawel Fedurek
- Division of Psychology, University of StirlingStirlingUnited Kingdom
| | - Cristina Gomes
- Tropical Conservation Institute, Florida International UniversityMiamiUnited States
| | - Therese Löhrich
- World Wide Fund for Nature, Dzanga Sangha Protected AreasBanguiCentral African Republic
- Robert Koch Institute, Epidemiology of Highly Pathogenic MicroorganismsBerlinGermany
| | - Virgile Manin
- Department of Human Behavior, Ecology and Culture, Max Planck Institute for Evolutionary AnthropologyLeipzigGermany
- Taï Chimpanzee Project, Centre Suisse de Recherches ScientifiquesAbidjanCôte d'Ivoire
| | - Anna Preis
- Department of Primatology, Max Planck Institute for Evolutionary AnthropologyLeipzigGermany
| | - Prince F Valé
- Taï Chimpanzee Project, Centre Suisse de Recherches ScientifiquesAbidjanCôte d'Ivoire
- Department of Primatology, Max Planck Institute for Evolutionary AnthropologyLeipzigGermany
- Centre Suisse de Recherches Scientifiques en Côte d'IvoireAbidjanCôte d'Ivoire
- Unité de Formation et de Recherche Biosciences, Université Félix Houphouët BoignyAbidjanCôte d'Ivoire
| | - Tobias Deschner
- Interim Group Primatology, Max Planck Institute for Evolutionary AnthropologyLeipzigGermany
| | - Roman M Wittig
- Department of Human Behavior, Ecology and Culture, Max Planck Institute for Evolutionary AnthropologyLeipzigGermany
- Taï Chimpanzee Project, Centre Suisse de Recherches ScientifiquesAbidjanCôte d'Ivoire
| | - Catherine Crockford
- Department of Human Behavior, Ecology and Culture, Max Planck Institute for Evolutionary AnthropologyLeipzigGermany
- Taï Chimpanzee Project, Centre Suisse de Recherches ScientifiquesAbidjanCôte d'Ivoire
- Institut des Sciences Cognitives, CNRSLyonFrance
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Enigk DK, Emery Thompson M, Machanda ZP, Wrangham RW, Muller MN. Female-directed aggression by adolescent male chimpanzees primarily constitutes dominance striving, not sexual coercion. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2021; 176:66-79. [PMID: 33938563 DOI: 10.1002/ajpa.24296] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2020] [Revised: 04/06/2021] [Accepted: 04/17/2021] [Indexed: 11/11/2022]
Abstract
OBJECTIVES Chimpanzees (Pan troglodytes) are notable for exhibiting high levels of male-to-female aggression. Much of this aggression from adult males serves sexually coercive functions. Despite being smaller and lower-ranking than adult males, adolescent males also engage in regular aggression against adult females. Here, we test whether the primary function of this aggression is sexual coercion, as in adult males, or, alternatively, whether adolescent males use aggression to establish social dominance over females. MATERIALS AND METHODS We analyzed 1771 copulations and 1812 instances of male-initiated aggression between adolescent males (aged nine through 14 years) and adult females across 21 years of observation of the Kanyawara chimpanzee community in Kibale National Park, Uganda. RESULTS Our test of the sexual coercion hypothesis revealed that adolescent males did not selectively target cycling females for aggression, nor did aggression against cycling females predict rates of copulation with those females. Our test of the social dominance hypothesis showed that males succeeded in dominating all adult females before, or soon after, dominating their first adult male. Additionally, we found that adolescent males dominated females approximately in the order of the females' own ranks, from the bottom to the top of the female hierarchy. DISCUSSION Our data illustrate that the establishment of social dominance was more important than sexual coercion in explaining patterns of adolescent male aggression toward females. In comparison, evidence for sexual coercion was clear and compelling in adult males. These findings highlight that the primary function of male-to-female aggression differs between adolescent and adult males.
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Affiliation(s)
- Drew K Enigk
- Department of Anthropology, University of New Mexico, Albuquerque, New Mexico, USA
| | - Melissa Emery Thompson
- Department of Anthropology, University of New Mexico, Albuquerque, New Mexico, USA.,Kibale Chimpanzee Project, Fort Portal, Uganda
| | - Zarin P Machanda
- Kibale Chimpanzee Project, Fort Portal, Uganda.,Department of Anthropology, Tufts University, Medford, USA
| | - Richard W Wrangham
- Kibale Chimpanzee Project, Fort Portal, Uganda.,Department of Human Evolutionary Biology, Harvard University, Cambridge, Massachusetts, USA
| | - Martin N Muller
- Department of Anthropology, University of New Mexico, Albuquerque, New Mexico, USA.,Kibale Chimpanzee Project, Fort Portal, Uganda
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Lonsdorf EV, Stanton MA, Wellens KR, Murray CM. Wild chimpanzee offspring exhibit adult-like foraging patterns around the age of weaning. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2021; 175:268-281. [PMID: 33713419 DOI: 10.1002/ajpa.24267] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 01/28/2021] [Accepted: 02/24/2021] [Indexed: 01/27/2023]
Abstract
OBJECTIVES The prolonged juvenile period exhibited by primates is an evolutionary conundrum. Here we examine wild chimpanzee feeding development in the context of two hypotheses regarding prolonged development in primates: the needing-to-learn hypothesis and the expensive brain hypothesis. MATERIAL AND METHODS We studied wild chimpanzee (Pan troglodytes schweinfurthii) offspring at Gombe National Park, Tanzania. We analyzed 41 years of observational behavioral data collected between 1975 and 2016 from 81 offspring. We characterized feeding development in the first 10 years of life via four different measures: (1) proportion of observation time spent feeding; (2) diet composition; (3) diet breadth; and (4) diet maturity as measured by similarity to maternal diet. We used mixed effects models to examine changes with age and by sex, while controlling for season. RESULTS Feeding time, diet breadth, and diet maturity exhibited the most substantial increases with age in the first 6 years, with no significant change thereafter. Males and females showed different patterns of change in diet breadth by age, but did not differ by age 10. Diet composition did not change significantly with age and did not differ by sex. DISCUSSION We found that chimpanzee offspring attained adult-like feeding behaviors between 4 and 6 years of age, concomitant with the completion of weaning. Thus, our data do not support the needing-to-learn feeding skills hypothesis of a prolonged juvenile period, but additional data are needed to evaluate how and when adolescent chimpanzees are able to make foraging decisions independent of their mothers. Existing data on growth provides support for the expensive brain hypothesis, however, these hypotheses are not necessarily mutually exclusive. As more studies across taxa accumulate sufficient datasets on a range of developmental metrics, we will be able to achieve a more robust understanding of prolonged development in primates.
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Affiliation(s)
- Elizabeth V Lonsdorf
- Department of Psychology, Franklin and Marshall College, Lancaster, Pennsylvania, USA.,Biological Foundations of Behavior Program, Franklin and Marshall College, Lancaster, Pennsylvania, USA
| | - Margaret A Stanton
- Department of Psychology, Franklin and Marshall College, Lancaster, Pennsylvania, USA.,Biological Foundations of Behavior Program, Franklin and Marshall College, Lancaster, Pennsylvania, USA.,School of Social and Behavioral Sciences, University of New England, Biddeford, Maine, USA
| | - Kaitlin R Wellens
- Department of Biology, Trinity Washington University, Washington, District of Columbia, USA
| | - Carson M Murray
- Center for the Advanced Study of Human Paleobiology, The George Washington University, Washington, District of Columbia, USA
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