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Friederici AD, Wittig RM, Anwander A, Eichner C, Gräßle T, Jäger C, Kirilina E, Lipp I, Düx A, Edwards LJ, Girard-Buttoz C, Jauch A, Kopp KS, Paquette M, Pine KJ, Unwin S, Haun DBM, Leendertz FH, McElreath R, Morawski M, Gunz P, Weiskopf N, Crockford C. Brain structure and function: a multidisciplinary pipeline to study hominoid brain evolution. Front Integr Neurosci 2024; 17:1299087. [PMID: 38260006 PMCID: PMC10800984 DOI: 10.3389/fnint.2023.1299087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2023] [Accepted: 12/07/2023] [Indexed: 01/24/2024] Open
Abstract
To decipher the evolution of the hominoid brain and its functions, it is essential to conduct comparative studies in primates, including our closest living relatives. However, strong ethical concerns preclude in vivo neuroimaging of great apes. We propose a responsible and multidisciplinary alternative approach that links behavior to brain anatomy in non-human primates from diverse ecological backgrounds. The brains of primates observed in the wild or in captivity are extracted and fixed shortly after natural death, and then studied using advanced MRI neuroimaging and histology to reveal macro- and microstructures. By linking detailed neuroanatomy with observed behavior within and across primate species, our approach provides new perspectives on brain evolution. Combined with endocranial brain imprints extracted from computed tomographic scans of the skulls these data provide a framework for decoding evolutionary changes in hominin fossils. This approach is poised to become a key resource for investigating the evolution and functional differentiation of hominoid brains.
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Affiliation(s)
- Angela D. Friederici
- Department of Neuropsychology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Roman M. Wittig
- Evolution of Brain Connectivity Project, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
- Institute for Cognitive Sciences Marc Jeannerod, UMR CNRS, University Claude Bernard Lyon, Bron, France
- Taï Chimpanzee Project, CSRS, Abidjan, Côte d'Ivoire
| | - Alfred Anwander
- Department of Neuropsychology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Cornelius Eichner
- Department of Neuropsychology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Tobias Gräßle
- Epidemiology of Highly Pathogenic Microorganisms, Robert Koch Institute, Berlin, Germany
| | - Carsten Jäger
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
- Medical Faculty, Center of Neuropathology and Brain Research, Paul Flechsig Institute, University of Leipzig, Leipzig, Germany
| | - Evgeniya Kirilina
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Ilona Lipp
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Ariane Düx
- Epidemiology of Highly Pathogenic Microorganisms, Robert Koch Institute, Berlin, Germany
- Helmholtz Institute for One Health, University of Greifswald, Greifswald, Germany
| | - Luke J. Edwards
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Cédric Girard-Buttoz
- Evolution of Brain Connectivity Project, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
- Institute for Cognitive Sciences Marc Jeannerod, UMR CNRS, University Claude Bernard Lyon, Bron, France
| | - Anna Jauch
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Kathrin S. Kopp
- Department of Comparative Cultural Psychology, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - Michael Paquette
- Department of Neuropsychology, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Kerrin J. Pine
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
| | - Steve Unwin
- School of Bioscience, University of Birmingham, Birmingham, United Kingdom
| | - Daniel B. M. Haun
- Department of Comparative Cultural Psychology, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - Fabian H. Leendertz
- Epidemiology of Highly Pathogenic Microorganisms, Robert Koch Institute, Berlin, Germany
- Helmholtz Institute for One Health, University of Greifswald, Greifswald, Germany
| | - Richard McElreath
- Department of Human Behavior, Ecology and Culture, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - Markus Morawski
- Medical Faculty, Center of Neuropathology and Brain Research, Paul Flechsig Institute, University of Leipzig, Leipzig, Germany
| | - Philipp Gunz
- Department of Human Origins, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - Nikolaus Weiskopf
- Department of Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany
- Faculty of Physics and Earth System Sciences, Felix Bloch Institute for Solid State Physics, Leipzig University, Leipzig, Germany
| | - Catherine Crockford
- Evolution of Brain Connectivity Project, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
- Institute for Cognitive Sciences Marc Jeannerod, UMR CNRS, University Claude Bernard Lyon, Bron, France
- Taï Chimpanzee Project, CSRS, Abidjan, Côte d'Ivoire
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2
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Mouginot M, Cheng L, Wilson ML, Feldblum JT, Städele V, Wroblewski EE, Vigilant L, Hahn BH, Li Y, Gilby IC, Pusey AE, Surbeck M. Reproductive inequality among males in the genus Pan. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220301. [PMID: 37381849 PMCID: PMC10291431 DOI: 10.1098/rstb.2022.0301] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Accepted: 03/21/2023] [Indexed: 06/30/2023] Open
Abstract
Reproductive inequality, or reproductive skew, drives natural selection, but has been difficult to assess, particularly for males in species with promiscuous mating and slow life histories, such as bonobos (Pan paniscus) and chimpanzees (Pan troglodytes). Although bonobos are often portrayed as more egalitarian than chimpanzees, genetic studies have found high male reproductive skew in bonobos. Here, we discuss mechanisms likely to affect male reproductive skew in Pan, then re-examine skew patterns using paternity data from published work and new data from the Kokolopori Bonobo Reserve, Democratic Republic of Congo and Gombe National Park, Tanzania. Using the multinomial index (M), we found considerable overlap in skew between the species, but the highest skew occurred among bonobos. Additionally, for two of three bonobo communities, but no chimpanzee communities, the highest ranking male had greater siring success than predicted by priority-of-access. Thus, an expanded dataset covering a broader demographic range confirms that bonobos have high male reproductive skew. Detailed comparison of data from Pan highlights that reproductive skew models should consider male-male dynamics including the effect of between-group competition on incentives for reproductive concessions, but also female grouping patterns and factors related to male-female dynamics including the expression of female choice. This article is part of the theme issue 'Evolutionary ecology of inequality'.
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Affiliation(s)
- Maud Mouginot
- Department of Anthropology, University of Minnesota, Minneapolis, MN 55455, USA
| | - Leveda Cheng
- Department of Human Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
- Max Planck Institute for Evolutionary Anthropology, Leipzig 04103, Germany
| | - Michael L. Wilson
- Department of Ecology, Evolution and Behavior, University of Minnesota, Saint Paul, MN 55108, USA
- Institute on the Environment, University of Minnesota, Saint Paul, MN 55108, USA
| | - Joseph T. Feldblum
- Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA
| | - Veronika Städele
- School of Human Evolution and Social Change, and Institute of Human Origins, Arizona State University, Tempe, AZ 85287, USA
- Cognitive Ethology Laboratory, German Primate Center, Göttingen 37077, Germany
| | - Emily E. Wroblewski
- Department of Anthropology, Washington University in St Louis, St Louis, MO 63130, USA
| | - Linda Vigilant
- Department of Primate Behavior and Evolution, Max Planck Institute for Evolutionary Anthropology, Leipzig 04103, Germany
| | - Beatrice H. Hahn
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Yingying Li
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Ian C. Gilby
- School of Human Evolution and Social Change, and Institute of Human Origins, Arizona State University, Tempe, AZ 85287, USA
| | - Anne E. Pusey
- Department of Evolutionary Anthropology, Duke University, Durham, NC 27708, USA
| | - Martin Surbeck
- Department of Human Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
- Max Planck Institute for Evolutionary Anthropology, Leipzig 04103, Germany
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3
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Rawlings BS, van Leeuwen EJC, Davila-Ross M. Chimpanzee communities differ in their inter- and intrasexual social relationships. Learn Behav 2023; 51:48-58. [PMID: 36725763 PMCID: PMC9971155 DOI: 10.3758/s13420-023-00570-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/05/2023] [Indexed: 02/03/2023]
Abstract
Male and female human social bonding strategies are culturally shaped, in addition to being genetically rooted. Investigating nonhuman primate bonding strategies across sex groups allows researchers to assess whether, as with humans, they are shaped by the social environment or whether they are genetically predisposed. Studies of wild chimpanzees show that in some communities males have strong bonds with other males, whereas in others, females form particularly strong intrasex bonds, potentially indicative of cultural differences across populations. However, excluding genetic or ecological explanations when comparing different wild populations is difficult. Here, we applied social network analysis to examine male and female social bonds in two neighbouring semiwild chimpanzee groups of comparable ecological conditions and subspecies compositions, but that differ in demographic makeup. Results showed differences in bonding strategies across the two groups. While female-female party co-residence patterns were significantly stronger in Group 1 (which had an even distribution of males and females) than in Group 2 (which had a higher proportion of females than males), there were no such differences for male-male or male-female associations. Conversely, female-female grooming bonds were stronger in Group 2 than in Group 1. We also found that, in line with captive studies but contrasting research with wild chimpanzees, maternal kinship strongly predicted proximity and grooming patterns across the groups. Our findings suggest that, as with humans, male and female chimpanzee social bonds are influenced by the specific social group they live in, rather than predisposed sex-based bonding strategies.
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Affiliation(s)
- Bruce S Rawlings
- Department of Psychology, Durham University, Durham, DH1 3LE, UK
- Durham Cultural Evolution Research Centre, Durham University, Durham, DH1 3LE, UK
- Centre for Comparative and Evolutionary Psychology, Psychology Department, University of Portsmouth, Portsmouth, PO1 2DY, UK
| | - Edwin J C van Leeuwen
- Animal Behaviour and Cognition, Department of Biology, University Utrecht, Utrecht, The Netherlands
- Department of Comparative Cultural Psychology, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103, Leipzig, Germany
| | - Marina Davila-Ross
- Centre for Comparative and Evolutionary Psychology, Psychology Department, University of Portsmouth, Portsmouth, PO1 2DY, UK.
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Nurmi NO, Sonnweber R, Schülke O, Moscovice LR, Deschner T, Hohmann G. Bonobo mothers have elevated urinary cortisol levels during early but not mid or late lactation. Primates 2023; 64:215-225. [PMID: 36565402 PMCID: PMC10006042 DOI: 10.1007/s10329-022-01044-7] [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: 04/14/2022] [Accepted: 12/02/2022] [Indexed: 12/25/2022]
Abstract
In mammals, the costs of reproduction are biased towards females. Lactation is particularly energetically expensive, and behavioral and physiological data indicate that maternal effort during lactation induces energetic stress. Another source of stress in females is male aggression directed towards them when they are cycling. Evaluating the costs of reproduction in wild and mobile animals can be a challenging task, and requires detailed information on state-dependent parameters such as hormone levels. Glucocorticoid (GC) levels are indicative of nutritional and social stress, and are widely used to assess the costs of reproduction. We investigated variation in urinary levels of cortisol, the main GC in female bonobos (Pan paniscus), between and within reproductive stages. Female chimpanzees (Pan troglodytes), the closest living relative of the bonobos, are often exposed to intense aggression from males, which causes a significant rise in their cortisol levels during the phase of their maximum fecundity. In bonobos, males compete for access to fertile females, but aggressive male mating strategies are absent in this species. Therefore, we expected that GC levels of cycling female bonobos would be lower than those of lactating females. Due to the long period of offspring care in bonobos, we expected that GC levels would remain elevated into the late stage of lactation, when immatures gain body weight but may still be nursed and carried by their mothers. We found elevated urinary GC levels only during the early stage of lactation. The GC levels of cycling females did not differ from those in the mid or late lactation stage. Behavioral strategies of female bonobos may allow them to compensate for the elevated energetic demands of lactation and prolonged maternal care.
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Affiliation(s)
- Niina O Nurmi
- Department of Behavioral Ecology, JFB Institute for Zoology/Anthropology, University of Goettingen, Göttingen, Germany.,Interim Group Primatology, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - Ruth Sonnweber
- Department of Behavioural and Cognitive Biology, University of Vienna, Vienna, Austria.
| | - Oliver Schülke
- Department of Behavioral Ecology, JFB Institute for Zoology/Anthropology, University of Goettingen, Göttingen, Germany.,Research Group Social Evolution in Primates, German Primate Center, Leibniz Institute for Primate Research, Göttingen, Germany
| | - Liza R Moscovice
- Institute of Behavioral Physiology, Leibniz Institute for Farm Animal Biology, Dummerstorf, Germany
| | - Tobias Deschner
- Interim Group Primatology, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - Gottfried Hohmann
- Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
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5
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Fox SA, Muller MN, González NT, Enigk DK, Machanda ZP, Otali E, Wrangham R, Thompson ME. Weak, but not strong, ties support coalition formation among wild female chimpanzees. Philos Trans R Soc Lond B Biol Sci 2023; 378:20210427. [PMID: 36440557 PMCID: PMC9703227 DOI: 10.1098/rstb.2021.0427] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 05/23/2022] [Indexed: 11/29/2022] Open
Abstract
In social species, individuals may be able to overcome competitive constraints on cooperation by leveraging relationships with familiar, tolerant partners. While strong social ties have been linked to cooperation in several social mammals, it is unclear the extent to which weak social ties can support cooperation, particularly among non-kin. We tested the hypothesis that weakly affiliative social relationships support cooperative coalition formation using 10 years of behavioural data on wild female chimpanzees. Female chimpanzees typically disperse and reside with non-kin as adults. Their social relationships are differentiated but often relatively weak, with few dyads sharing strong bonds. Females occasionally form aggressive coalitions together. Three measures of relationship quality-party association, five-metre proximity and whether a dyad groomed-positively predicted coalitions, indicating that relationship quality influenced coalition partnerships. However, dyads that groomed frequently did not form more coalitions than dyads that groomed occasionally, and kin did not cooperate more than expected given their relationship quality. Thus, strong bonds and kinship did not bolster cooperation. We conclude that cooperative coalitions among female chimpanzees depend on social tolerance but do not require strong bonds. Our findings highlight social tolerance as a distinct pathway through which females can cultivate cooperative relationships. This article is part of the theme issue 'Cooperation among women: evolutionary and cross-cultural perspectives'.
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Affiliation(s)
- Stephanie A. Fox
- Department of Anthropology, University of New Mexico, Albuquerque, NM 87131, USA
| | - Martin N. Muller
- Department of Anthropology, University of New Mexico, Albuquerque, NM 87131, USA
| | - Nicole Thompson González
- Department of Anthropology, University of California Santa Barbara, Santa Barbara, CA 93106-3210, USA
| | - Drew K. Enigk
- Department of Anthropology, University of New Mexico, Albuquerque, NM 87131, USA
| | - Zarin P. Machanda
- Department of Anthropology, Tufts University, Medford, MA 02155, USA
| | - Emily Otali
- Kibale Chimpanzee Project, Fort Portal, Uganda
| | - Richard Wrangham
- Department of Human Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
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6
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Fasbender D, Yamba U, Keuk K, Hart T, Hart J, Furuichi T. Bonobo social organization at the seasonal forest‐savanna ecotone of the Lomami national park. Am J Primatol 2022; 84:e23448. [DOI: 10.1002/ajp.23448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2022] [Revised: 08/11/2022] [Accepted: 10/04/2022] [Indexed: 11/07/2022]
Affiliation(s)
- David Fasbender
- Department of Primatology and Wildlife Science, Graduate School of Science Kyoto University Inuyama Japan
| | - Uyulu Yamba
- Institut Congolais pour la Conservation de la Nature Kinshasa Democratic Republic of Congo
| | - Kenneth Keuk
- Department of Primatology and Wildlife Science, Graduate School of Science Kyoto University Inuyama Japan
| | - Terese Hart
- TL2 Project of the Frankfurt Zoological Society Kinshasa Democratic Republic of Congo
| | - John Hart
- TL2 Project of the Frankfurt Zoological Society Kinshasa Democratic Republic of Congo
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7
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Why bonobos show a high reproductive skew towards high-ranking males: analyses for association and mating patterns concerning female sexual states. Primates 2022; 63:483-494. [PMID: 35931876 DOI: 10.1007/s10329-022-01004-1] [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: 03/14/2022] [Accepted: 07/13/2022] [Indexed: 10/16/2022]
Abstract
Among non-human primates, male dominance rank is not necessarily a good indicator of mating success, and relationships between male dominance rank and mating or reproductive success are affected by female behavior and sexual states implying their probability of conception. Although comparisons of the behavior of male chimpanzees (Pan troglodytes) and bonobos (Pan paniscus) suggest that the effect of male dominance rank on mating success is expected to be less prominent in bonobos, recent genetic studies have shown that high-ranking male reproductive skew is higher in bonobos than in chimpanzees. One possible reason for the higher reproductive skew in bonobos could be that female behavior and their sexual states may have much more influence on male mating and reproductive success in bonobos than in chimpanzees. In the current study on bonobos, we conducted focal animal observation of females and analyzed the influence of female sexual swelling, the number of days after parturition, and dominance rank of males on female associations, and copulation with adult males. Our results showed that females with maximum swelling (MS) had more proximity with high-ranking males and copulated more frequently with higher-ranking males than with lower-ranking males. Females for whom longer time had elapsed since parturition, and therefore had higher probabilities of conception, had 5-m proximity with adult males more frequently than females whom shorter time had elapsed since parturition, but did not have more copulation with adult males. Females with MS had proximity and copulated with high-ranking males frequently, which partly explains why the reproductive skew is so high in bonobos. These results are discussed in relation to previous hypotheses on the influence of long-lasting mother-son relationships on mating success of males and on the contribution of female receptivity during non-conceptive nursing periods to moderate intermale aggression in bonobos.
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8
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Human Females as a Dispersal-Egalitarian Species: A Hypothesis about Women and Status. ADAPTIVE HUMAN BEHAVIOR AND PHYSIOLOGY 2022. [DOI: 10.1007/s40750-022-00191-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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9
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Davidian E, Surbeck M, Lukas D, Kappeler PM, Huchard E. The eco-evolutionary landscape of power relationships between males and females. Trends Ecol Evol 2022; 37:706-718. [PMID: 35597702 DOI: 10.1016/j.tree.2022.04.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Revised: 04/04/2022] [Accepted: 04/06/2022] [Indexed: 11/17/2022]
Abstract
In animal societies, control over resources and reproduction is often biased towards one sex. Yet, the ecological and evolutionary underpinnings of male-female power asymmetries remain poorly understood. We outline a comprehensive framework to quantify and predict the dynamics of male-female power relationships within and across mammalian species. We show that male-female power relationships are more nuanced and flexible than previously acknowledged. We then propose that enhanced reproductive control over when and with whom to mate predicts social empowerment across ecological and evolutionary contexts. The framework explains distinct pathways to sex-biased power: coercion and male-biased dimorphism constitute a co-evolutionary highway to male power, whereas female power emerges through multiple physiological, morphological, behavioural, and socioecological pathways.
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Affiliation(s)
- Eve Davidian
- Ngorongoro Hyena Project, Ngorongoro Conservation Area, Arusha, Tanzania.
| | - Martin Surbeck
- Department of Human Evolutionary Biology, Harvard University, Cambridge, MA, USA
| | - Dieter Lukas
- Department of Human Behavior, Ecology and Culture, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - Peter M Kappeler
- German Primate Center, Behavioral Ecology Unit, Leibniz Institute of Primate Biology, Göttingen, Germany; Department of Sociobiology and Anthropology, University of Göttingen, Göttingen, Germany
| | - Elise Huchard
- Anthropologie Évolutive, Institut des Sciences de l'Évolution de Montpellier (ISEM), Montpellier, France.
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10
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Cheng L, Shaw A, Surbeck M. Mothers stick together: how the death of an infant affects female social relationships in a group of wild bonobos (Pan paniscus). Primates 2022; 63:343-353. [PMID: 35435534 PMCID: PMC9273548 DOI: 10.1007/s10329-022-00986-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 03/21/2022] [Indexed: 11/28/2022]
Abstract
Sociality is widespread among group-living primates and is beneficial in many ways. Sociality amongst female bonobos (Pan paniscus) has been proposed to have evolved as a female counterstrategy to male infanticide and sexual coercion. In male-philopatric bonobo societies, females mostly form relationships with unrelated females. Among these social relationships, it has been proposed that females with infants (also referred to as mothers) tend to have strong relationships with each other (mother-bonding hypothesis). In this paper, we use the case of an infant death in a group of wild bonobos in the Kokolopori Bonobo Reserve, Democratic Republic of Congo, to test this hypothesis. By using dyadic sociality indices for grooming, proximity, and aggression, we investigated whether the infant death influenced dyadic relationships the mother had with other group members. Before the infant death, grooming index (GI) and proximity index (PI) scores were the highest between the focal mother and another mother. After the death, the relationship of this mother dyad weakened, as indicated by lower GI and PI scores, whereas the relationship of another mother dyad became stronger. Aggression index scores among the mothers were comparable before and after the death, suggesting that changes in mother affiliative relationships were not a by-product of changes in overall interaction frequencies. Also, PI scores increased between the focal mother and three non-mothers after the death. Collectively, the shift in social dynamics between the focal mother and other group members after the infant death partially supported the mother-bonding hypothesis.
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Affiliation(s)
- Leveda Cheng
- Department of Human Evolutionary Biology, Harvard University, 11 Divinity Avenue, Cambridge, MA, 02138, USA.
- Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103, Leipzig, Germany.
| | - Amber Shaw
- Department of Human Evolutionary Biology, Harvard University, 11 Divinity Avenue, Cambridge, MA, 02138, USA
| | - Martin Surbeck
- Department of Human Evolutionary Biology, Harvard University, 11 Divinity Avenue, Cambridge, MA, 02138, USA
- Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103, Leipzig, Germany
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