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Hagen RV, Scelza BA. Sex ratios and gender norms: why both are needed to understand sexual conflict in humans. EVOLUTIONARY HUMAN SCIENCES 2024; 6:e10. [PMID: 38414809 PMCID: PMC10897493 DOI: 10.1017/ehs.2024.3] [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: 09/14/2023] [Revised: 12/26/2023] [Accepted: 12/28/2023] [Indexed: 02/29/2024] Open
Abstract
Sexual conflict theory has been successfully applied to predict how in non-human animal populations, sex ratios can lead to conflicting reproductive interests of females and males and affect their bargaining positions in resolving such conflicts of interests. Recently this theory has been extended to understand the resolution of sexual conflict in humans, but with mixed success. We argue that an underappreciation of the complex relationship between gender norms and sex ratios has hampered a successful understanding of sexual conflict in humans. In this paper, we review and expand upon existing theory to increase its applicability to humans, where gender norms regulate sex ratio effects on sexual conflict. Gender norms constrain who is on the marriage market and how they are valued, and may affect reproductive decision-making power. Gender norms can also directly affect sex ratios, and we hypothesize that they structure how individuals respond to market value gained or lost through biased sex ratios. Importantly, gender norms are in part a product of women's and men's sometimes conflicting reproductive interests, but these norms are also subject to other evolutionary processes. An integration of sexual conflict theory and cultural evolutionary theory is required to allow for a full understanding of sexual conflict in humans.
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Affiliation(s)
- Renée V Hagen
- Department of Anthropology, University of California, Los Angeles. United States of America
| | - Brooke A Scelza
- Department of Anthropology, University of California, Los Angeles. United States of America
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2
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Ember CR, McCarter A, Ringen E. Uniformity in Dress: A Worldwide Cross-Cultural Comparison. HUMAN NATURE (HAWTHORNE, N.Y.) 2023; 34:359-380. [PMID: 37735330 DOI: 10.1007/s12110-023-09457-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 08/16/2023] [Indexed: 09/23/2023]
Abstract
Focusing on clothing and adornment (dress), this worldwide cross-cultural comparison asks why people in some societies appear to dress in uniform or standardized ways, whereas in other societies individuals display considerable variability in dress. The broader research question is why some societies have more within-group variation than others. Hypotheses are tested on 80 societies drawn from the Standard Cross-Cultural Sample (SCCS). The central hypotheses consider the impact of general societal tightness or looseness, degree of egalitarianism as well as other aspects of societal complexity, and the role of resource stress on dress standardization. Exploratory methods identify four latent constructs of dress from newly coded variables, one latent construct for tightness/looseness, and one latent construct for resource stress. As expected, (1) increased societal tightness was positively related to increased standardization and rules regarding dress and (2) increased resource stress is generally related to more standardization of dress and rules regarding adornment. However, contrary to theoretical expectations, the predictors of tightness-looseness differ from the predictors of dress. Most importantly, resource stress negatively predicts tightness but positively predicts three of the latent dress constructs. The relationship between dress standardization and societal complexity may be curvilinear, with mid-range societies having more standardization. Although some of the theorized relationships are supported (including that standardization of dress is predicted by societal tightness and more resource stress), at the end of paper we discuss some puzzling findings, speculate about possible explanations, and suggest further lines of research.
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Affiliation(s)
- Carol R Ember
- Human Relations Area Files, Yale University, 755 Prospect Street, New Haven, CT, 06517, USA.
| | - Abbe McCarter
- Human Relations Area Files, Yale University, 755 Prospect Street, New Haven, CT, 06517, USA
- Results for Development, Washington, DC, USA
| | - Erik Ringen
- Emory University, Atlanta, GA, USA
- NCCR@LiRi, Center for the Interdisciplinary Study of Language Evolution, University of Zurich, Zurich, Switzerland
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3
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Lawson DW, Alami S, Somefun OD. Gendered conflict in the human family. EVOLUTIONARY HUMAN SCIENCES 2023; 5:e12. [PMID: 37587929 PMCID: PMC10426121 DOI: 10.1017/ehs.2023.8] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Accepted: 04/02/2023] [Indexed: 08/18/2023] Open
Abstract
Sexual conflict is a thriving area of animal behaviour research. Yet parallel research in the evolutionary human sciences remains underdeveloped and has become mired by controversy. In this special collection, we aim to invigorate the study of fitness-relevant conflicts between women and men, advocating for three synergistic research priorities. First, we argue that a commitment to diversity is required to innovate the field, achieve ethical research practice, and foster fruitful dialogue with neighbouring social sciences. Accordingly, we have prioritised issues of diversity as editors, aiming to stimulate new connections and perspectives. Second, we call for greater recognition that human sex/gender roles and accompanying conflict behaviours are both subject to natural selection and culturally determined. This motivates our shift in terminology from sexual to gendered conflict when addressing human behaviour, countering stubborn tendencies to essentialise differences between women and men and directing attention to the role of cultural practices, normative sanctions and social learning in structuring conflict battlegrounds. Finally, we draw attention to contemporary policy concerns, including the wellbeing consequences of marriage practices and the gendered implications of market integration. Focus on these themes, combined with attendance to the dangers of ethnocentrism, promises to inform culturally sensitive interventions promoting gender equality worldwide.
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Affiliation(s)
- David W Lawson
- Department of Anthropology, University of California Santa Barbara, USA
| | - Sarah Alami
- The School of Collective Intelligence, Mohammed VI Polytechnic University, Morocco
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4
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Garfield ZH, Ringen EJ, Buckner W, Medupe D, Wrangham RW, Glowacki L. Norm violations and punishments across human societies. EVOLUTIONARY HUMAN SCIENCES 2023; 5:e11. [PMID: 37587937 PMCID: PMC10426015 DOI: 10.1017/ehs.2023.7] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Revised: 03/17/2023] [Accepted: 04/01/2023] [Indexed: 08/18/2023] Open
Abstract
Punishments for norm violations are hypothesised to be a crucial component of the maintenance of cooperation in humans but are rarely studied from a comparative perspective. We investigated the degree to which punishment systems were correlated with socioecology and cultural history. We took data from the Standard Cross-Cultural Sample database and coded ethnographic documents from a sample of 131 largely non-industrial societies. We recorded whether punishment for norm violations concerned adultery, religion, food, rape or war cowardice and whether sanctions were reputational, physical, material or execution. We used Bayesian phylogenetic regression modelling to test for culture-level covariation. We found little evidence of phylogenetic signals in evidence for punishment types, suggesting that punishment systems change relatively quickly over cultural evolutionary history. We found evidence that reputational punishment was associated with egalitarianism and the absence of food storage; material punishment was associated with the presence of food storage; physical punishment was moderately associated with greater dependence on hunting; and execution punishment was moderately associated with social stratification. Taken together, our results suggest that the role and kind of punishment vary both by the severity of the norm violation, but also by the specific socio-economic system of the society.
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Affiliation(s)
- Zachary H. Garfield
- Institute for Advanced Study in Toulouse, Université de Toulouse 1 Capitole, Toulouse, France
| | - Erik J. Ringen
- Department of Anthropology, Emory University, Atlanta, GA, USA
| | - William Buckner
- Department of Anthropology, Boston University, Boston, MA, USA
| | - Dithapelo Medupe
- Department of Anthropology, Pennsylvania State University, PA, USA
| | | | - Luke Glowacki
- Department of Anthropology, Boston University, Boston, MA, USA
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5
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Šaffa G, Duda P, Zrzavý J. Paternity Uncertainty and Parent-Offspring Conflict Explain Restrictions on Female Premarital Sex across Societies. HUMAN NATURE (HAWTHORNE, N.Y.) 2022; 33:215-235. [PMID: 35633467 DOI: 10.1007/s12110-022-09426-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 05/07/2022] [Indexed: 06/15/2023]
Abstract
Although norms of premarital sex vary cross-culturally, the sexuality of adolescent girls has been consistently more restricted than that of adolescent boys. Three major theories that attempt to explain restrictions on female premarital sex (FPS) concern male, female, and parental control. These competing theories have not been tested against each other cross-culturally. In this study, we do this using a sample of 128 nonindustrial societies and socioecological predictors capturing extramarital sex, paternal care, female status, sex ratio, parental control over a daughter's mate choice, residence, and marriage transactions, while also controlling for phylogenetic non-independence across societies. We found that multiple parties benefit from restrictions on FPS. Specifically, FPS is more restricted in societies intolerant of extramarital sex and where men transfer property to their children (male control), as well as where marriages are arranged by parents (parental control). Both paternity uncertainty (partitioned among marital fidelity and paternal investment) and parent-offspring conflict (prompting parents to control their daughter's sexuality) were identified as possible mechanisms of FPS restrictions. The evidence for female control is ambiguous, mainly because it can be equally well interpreted as both male control and parental control, and because fathers, rather than mothers, are often the primary decision makers about a daughter's mate choice. Our results also emphasize the importance of social roles, rather than stereotyped sex roles, as a more useful approach to understanding the evolution of FPS restrictions.
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Affiliation(s)
- Gabriel Šaffa
- Department of Zoology, Faculty of Science, University of South Bohemia, Branišovská 1760, 370 05, České Budějovice, Czechia.
| | - Pavel Duda
- Department of Zoology, Faculty of Science, University of South Bohemia, Branišovská 1760, 370 05, České Budějovice, Czechia
| | - Jan Zrzavý
- Department of Zoology, Faculty of Science, University of South Bohemia, Branišovská 1760, 370 05, České Budějovice, Czechia
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6
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Šaffa G, Zrzavý J, Duda P. Global phylogenetic analysis reveals multiple origins and correlates of genital mutilation/cutting. Nat Hum Behav 2022; 6:635-645. [PMID: 35361908 DOI: 10.1038/s41562-022-01321-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2021] [Accepted: 02/18/2022] [Indexed: 12/26/2022]
Abstract
Genital mutilation/cutting is costly in terms of health, survival and reproduction, and the long-term maintenance of these practices is an evolutionary conundrum. Previous studies have suggested a mate-guarding function or various signalling functions of genital mutilation/cutting. Here we use phylogenetic comparative methods and two global ethnographic samples to study the origins and socio-ecological correlates of major types of female and male genital mutilation/cutting. Male genital mutilation/cutting probably originated in polygynous societies with separate residence of co-wives, supporting a mate-guarding function. Female genital mutilation/cutting originated subsequently and almost exclusively in societies already practising male genital mutilation/cutting, where it may have become a signal of chastity. Both have originated multiple times, some as early as in the mid-Holocene (5,000-7,000 years ago), considerably predating the earliest archaeological evidence and written records. Genital mutilation/cutting co-evolves with and may help maintain fundamental social structures, hindering efforts to change these cultural practices.
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Affiliation(s)
- Gabriel Šaffa
- Department of Zoology, Faculty of Science, University of South Bohemia, České Budějovice, Czechia
| | - Jan Zrzavý
- Department of Zoology, Faculty of Science, University of South Bohemia, České Budějovice, Czechia
| | - Pavel Duda
- Department of Zoology, Faculty of Science, University of South Bohemia, České Budějovice, Czechia.
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7
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Itao K, Kaneko K. Emergence of kinship structures and descent systems: multi-level evolutionary simulation and empirical data analysis. Proc Biol Sci 2022; 289:20212641. [PMID: 35193405 PMCID: PMC8864366 DOI: 10.1098/rspb.2021.2641] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2021] [Accepted: 01/25/2022] [Indexed: 11/21/2022] Open
Abstract
In many indigenous societies, people are categorized into several cultural groups, or clans, within which they believe they share ancestors. Clan attributions provide certain rules for marriage and descent. Such rules between clans constitute kinship structures. Anthropologists have revealed several kinship structures. Here, we propose an agent-based model of indigenous societies to reveal the evolution of kinship structures. In the model, several societies compete. Societies themselves comprise multiple families with parameters for cultural traits and mate preferences. These values determine with whom each family cooperates and competes, and they are transmitted to a new generation with mutation. The growth rate of each family is determined by the number of cooperators and competitors. Through this multi-level evolution, family traits and preferences diverge to form clusters that can be regarded as clans. Subsequently, kinship structures emerge, including dual organization and generalized or restricted exchange, as well as patrilineal, matrilineal and double descent systems. These structures emerge depending on the necessity of cooperation and the strength of mating competition. Their dependence is also estimated analytically. Finally, statistical analysis using the Standard Cross-Cultural Sample, a global ethnographic database, empirically verified the theoretical results. Such collaboration between theoretical and empirical approaches will unveil universal features in anthropology.
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Affiliation(s)
- Kenji Itao
- Department of Basic Science, Graduate School of Arts and Sciences, University of Tokyo, Komaba 3-8-1, Meguro-ku, Tokyo 153-8902, Japan
| | - Kunihiko Kaneko
- Department of Basic Science, Graduate School of Arts and Sciences, University of Tokyo, Komaba 3-8-1, Meguro-ku, Tokyo 153-8902, Japan
- Research Center for Complex Systems Biology, University of Tokyo, Komaba 3-8-1, Meguro-ku, Tokyo 153-8902, Japan
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8
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Lukas D, Towner M, Borgerhoff Mulder M. The potential to infer the historical pattern of cultural macroevolution. Philos Trans R Soc Lond B Biol Sci 2021; 376:20200057. [PMID: 33993769 PMCID: PMC8126461 DOI: 10.1098/rstb.2020.0057] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/10/2021] [Indexed: 12/17/2022] Open
Abstract
Phylogenetic analyses increasingly take centre-stage in our understanding of the processes shaping patterns of cultural diversity and cultural evolution over time. Just as biologists explain the origins and maintenance of trait differences among organisms using phylogenetic methods, so anthropologists studying cultural macroevolutionary processes use phylogenetic methods to uncover the history of human populations and the dynamics of culturally transmitted traits. In this paper, we revisit concerns with the validity of these methods. Specifically, we use simulations to reveal how properties of the sample (size, missing data), properties of the tree (shape) and properties of the traits (rate of change, number of variants, transmission mode) might influence the inferences that can be drawn about trait distributions across a given phylogeny and the power to discern alternative histories. Our approach shows that in two example datasets specific combinations of properties of the sample, of the tree and of the trait can lead to potentially high rates of Type I and Type II errors. We offer this simulation tool to help assess the potential impact of this list of persistent perils in future cultural macroevolutionary work. This article is part of the theme issue 'Foundations of cultural evolution'.
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Affiliation(s)
- Dieter Lukas
- Department of Human Behavior, Ecology and Culture, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany
| | - Mary Towner
- Department of Integrative Biology, Oklahoma State University, Stillwater, OK 74078, USA
| | - Monique Borgerhoff Mulder
- Department of Human Behavior, Ecology and Culture, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany
- Department of Anthropology, University of California Davis, Davis, CA 95616, USA
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9
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Evans CL, Greenhill SJ, Watts J, List JM, Botero CA, Gray RD, Kirby KR. The uses and abuses of tree thinking in cultural evolution. Philos Trans R Soc Lond B Biol Sci 2021; 376:20200056. [PMID: 33993767 PMCID: PMC8126464 DOI: 10.1098/rstb.2020.0056] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/11/2021] [Indexed: 11/13/2022] Open
Abstract
Modern phylogenetic methods are increasingly being used to address questions about macro-level patterns in cultural evolution. These methods can illuminate the unobservable histories of cultural traits and identify the evolutionary drivers of trait change over time, but their application is not without pitfalls. Here, we outline the current scope of research in cultural tree thinking, highlighting a toolkit of best practices to navigate and avoid the pitfalls and 'abuses' associated with their application. We emphasize two principles that support the appropriate application of phylogenetic methodologies in cross-cultural research: researchers should (1) draw on multiple lines of evidence when deciding if and which types of phylogenetic methods and models are suitable for their cross-cultural data, and (2) carefully consider how different cultural traits might have different evolutionary histories across space and time. When used appropriately phylogenetic methods can provide powerful insights into the processes of evolutionary change that have shaped the broad patterns of human history. This article is part of the theme issue 'Foundations of cultural evolution'.
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Affiliation(s)
- Cara L. Evans
- Department of Linguistic and Cultural Evolution, Max Planck Institute for the Science of Human History, Jena 07745, Germany
| | - Simon J. Greenhill
- Department of Linguistic and Cultural Evolution, Max Planck Institute for the Science of Human History, Jena 07745, Germany
- ARC Centre of Excellence for the Dynamics of Language, ANU College of Asia and the Pacific, Australian National University, Canberra 2700, Australia
| | - Joseph Watts
- Religion Programme, University of Otago, Dunedin 9016, New Zealand
- Centre for Research on Evolution, Belief and Behaviour, University of Otago, Dunedin 9016, New Zealand
| | - Johann-Mattis List
- Department of Linguistic and Cultural Evolution, Max Planck Institute for the Science of Human History, Jena 07745, Germany
| | - Carlos A. Botero
- Department of Biology, Washington University in St Louis, St Louis, MO 63130, USA
| | - Russell D. Gray
- Department of Linguistic and Cultural Evolution, Max Planck Institute for the Science of Human History, Jena 07745, Germany
- School of Psychology, University of Auckland, Auckland 1010, New Zealand
| | - Kathryn R. Kirby
- Department of Linguistic and Cultural Evolution, Max Planck Institute for the Science of Human History, Jena 07745, Germany
- Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada M5S 3B2
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10
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Hooper PL, Kaplan HS, Jaeggi AV. Gains to cooperation drive the evolution of egalitarianism. Nat Hum Behav 2021; 5:847-856. [PMID: 33649461 DOI: 10.1038/s41562-021-01059-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Accepted: 01/21/2021] [Indexed: 01/30/2023]
Abstract
What conditions favour egalitarianism, that is, muted hierarchies with relatively equal distributions of resources? Here, we combine the hawk-dove and prisoner's dilemma games to model the effects of economic defensibility, costs of competition and gains from cooperation on egalitarianism, operationalized as the absence of hawks. We show that a 'leveller' strategy, which punishes hawkishness in the hawk-dove game with defection in the prisoner's dilemma, can be evolutionarily stable provided that the gains from cooperation are high relative to the benefits of hawkishness. Under these conditions, rare mutant levellers select for hawks that acquiesce to punishment by playing dove. If these 'acquiescent hawks' become common, levellers outperform hawks and establish a new egalitarian equilibrium. An analysis of human foraging groups corroborates these results, as groups with a greater reliance on cooperation are more egalitarian. Cooperation fosters greater equality when individuals can withhold its benefits from would-be dominant individuals.
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Affiliation(s)
- Paul L Hooper
- Department of Anthropology, University of New Mexico, Albuquerque, NM, USA. .,Economic Science Institute, Chapman University, Orange, CA, USA.
| | | | - Adrian V Jaeggi
- Institute of Evolutionary Medicine, University of Zurich, Zurich, Switzerland
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11
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Ecological variation and institutionalized inequality in hunter-gatherer societies. Proc Natl Acad Sci U S A 2021; 118:2016134118. [PMID: 33758100 DOI: 10.1073/pnas.2016134118] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Research examining institutionalized hierarchy tends to focus on chiefdoms and states, while its emergence among small-scale societies remains poorly understood. Here, we test multiple hypotheses for institutionalized hierarchy, using environmental and social data on 89 hunter-gatherer societies along the Pacific coast of North America. We utilize statistical models capable of identifying the main correlates of sustained political and economic inequality, while controlling for historical and spatial dependence. Our results indicate that the most important predictors relate to spatiotemporal distribution of resources. Specifically, higher reliance on and ownership of clumped aquatic (primarily salmon) versus wild plant resources is associated with greater political-economic inequality, measuring the latter as a composite of internal social ranking, unequal access to food resources, and presence of slavery. Variables indexing population pressure, scalar stress, and intergroup conflict exhibit little or no correlation with variation in inequality. These results are consistent with models positing that hierarchy will emerge when individuals or coalitions (e.g., kin groups) control access to economically defensible, highly clumped resource patches, and use this control to extract benefits from subordinates, such as productive labor and political allegiance in a patron-client system. This evolutionary ecological explanation might illuminate how and why institutionalized hierarchy emerges among many small-scale societies.
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12
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Atari M, Lai MHC, Dehghani M. Sex differences in moral judgements across 67 countries. Proc Biol Sci 2020; 287:20201201. [PMID: 33081618 DOI: 10.1098/rspb.2020.1201] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Most of the empirical research on sex differences and cultural variations in morality has relied on within-culture analyses or small-scale cross-cultural data. To further broaden the scientific understanding of sex differences in morality, the current research relies on two international samples to provide the first large-scale examination of sex differences in moral judgements nested within cultures. Using a sample from 67 countries (Study 1; n = 336 691), we found culturally variable sex differences in moral judgements, as conceptualized by Moral Foundations Theory. Women consistently scored higher than men on Care, Fairness, and Purity. By contrast, sex differences in Loyalty and Authority were negligible and highly variable across cultures. Country-level sex differences in moral judgements were also examined in relation to cultural, socioeconomic, and gender-equality indicators revealing that sex differences in moral judgements are larger in individualist, Western, and gender-equal societies. In Study 2 (19 countries; n = 11 969), these results were largely replicated using Bayesian multi-level modelling in a distinct sample. The findings were robust when incorporating cultural non-independence of countries into the models. Specifically, women consistently showed higher concerns for Care, Fairness, and Purity in their moral judgements than did men. Sex differences in moral judgements were larger in individualist and gender-equal societies with more flexible social norms. We discuss the implications of these findings for the ongoing debate about the origin of sex differences and cultural variations in moral judgements as well as theoretical and pragmatic implications for moral and evolutionary psychology.
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Affiliation(s)
- Mohammad Atari
- Department of Psychology, University of Southern California, Los Angeles, CA, USA.,Brain and Creativity Institute, University of Southern California, Los Angeles, CA, USA
| | - Mark H C Lai
- Department of Psychology, University of Southern California, Los Angeles, CA, USA
| | - Morteza Dehghani
- Department of Psychology, University of Southern California, Los Angeles, CA, USA.,Brain and Creativity Institute, University of Southern California, Los Angeles, CA, USA.,Department of Computer Science, University of Southern California, Los Angeles, CA, USA
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13
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Martin JS, Ringen EJ, Duda P, Jaeggi AV. Harsh environments promote alloparental care across human societies. Proc Biol Sci 2020; 287:20200758. [PMID: 32811302 DOI: 10.1098/rspb.2020.0758] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Alloparental care is central to human life history, which integrates exceptionally short interbirth intervals and large birth size with an extended period of juvenile dependency and increased longevity. Formal models, previous comparative research, and palaeoanthropological evidence suggest that humans evolved higher levels of cooperative childcare in response to increasingly harsh environments. Although this hypothesis remains difficult to test directly, the relative importance of alloparental care varies across human societies, providing an opportunity to assess how local social and ecological factors influence the expression of this behaviour. We therefore, investigated associations between alloparental infant care and socioecology across 141 non-industrialized societies. We predicted increased alloparental care in harsher environments, due to the fitness benefits of cooperation in response to shared ecological challenges. We also predicted that starvation would decrease alloparental care, due to prohibitive energetic costs. Using Bayesian phylogenetic multilevel models, we tested these predictions while accounting for potential confounds as well as for population history. Consistent with our hypotheses, we found increased alloparental infant care in regions characterized by both reduced climate predictability and relatively lower average temperatures and precipitation. We also observed reduced alloparental care under conditions of high starvation. These results provide evidence of plasticity in human alloparenting in response to ecological contexts, comparable to previously observed patterns across avian and mammalian cooperative breeders. This suggests convergent social evolutionary processes may underlie both inter- and intraspecific variation in alloparental care.
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Affiliation(s)
- J S Martin
- Human Ecology Group, Institute of Evolutionary Medicine, University of Zurich, Zurich, Switzerland.,Department of Anthropology, Emory University, Atlanta, GA, USA
| | - E J Ringen
- Department of Anthropology, Emory University, Atlanta, GA, USA
| | - P Duda
- Department of Zoology, University of South Bohemia, Ceske Budejovice, Jihočeský, Czechia
| | - A V Jaeggi
- Human Ecology Group, Institute of Evolutionary Medicine, University of Zurich, Zurich, Switzerland.,Department of Anthropology, Emory University, Atlanta, GA, USA
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14
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Hrnčíř V, Duda P, Šaffa G, Květina P, Zrzavý J. Identifying post-marital residence patterns in prehistory: A phylogenetic comparative analysis of dwelling size. PLoS One 2020; 15:e0229363. [PMID: 32092129 PMCID: PMC7039508 DOI: 10.1371/journal.pone.0229363] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Accepted: 02/04/2020] [Indexed: 11/19/2022] Open
Abstract
Post-marital residence patterns are an important aspect of human social organization. However, identifying such patterns in prehistoric societies is challenging since they leave almost no direct traces in archaeological records. Cross-cultural researchers have attempted to identify correlates of post-marital residence through the statistical analysis of ethnographic data. Several studies have demonstrated that, in agricultural societies, large dwellings (over ca. 65 m2) are associated with matrilocality (spouse resides with or near the wife’s family), whereas smaller dwellings are associated with patrilocality (spouse resides with or near the husband’s family). In the present study, we tested the association between post-marital residence and dwelling size (average house floor area) using phylogenetic comparative methods and a global sample of 86 pre-industrial societies, 22 of which were matrilocal. Our analysis included the presence of agriculture, sedentism, and durability of house construction material as additional explanatory variables. The results confirm a strong association between matrilocality and dwelling size, although very large dwellings (over ca. 200 m2) were found to be associated with all types of post-marital residence. The best model combined dwelling size, post-marital residence pattern, and sedentism, the latter being the single best predictor of house size. The effect of agriculture on dwelling size becomes insignificant once the fixity of settlement is taken into account. Our results indicate that post-marital residence and house size evolve in a correlated fashion, namely that matrilocality is a predictable response to an increase in dwelling size. As such, we suggest that reliable inferences about the social organization of prehistoric societies can be made from archaeological records.
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Affiliation(s)
- Václav Hrnčíř
- Department of Archaeology, Faculty of Arts, Charles University, Prague, Czechia
- Institute of Archaeology of the Czech Academy of Sciences, Prague, Czechia
- * E-mail:
| | - Pavel Duda
- Department of Zoology, Faculty of Science, University of South Bohemia, České Budějovice, Czechia
| | - Gabriel Šaffa
- Department of Zoology, Faculty of Science, University of South Bohemia, České Budějovice, Czechia
| | - Petr Květina
- Institute of Archaeology of the Czech Academy of Sciences, Prague, Czechia
| | - Jan Zrzavý
- Department of Zoology, Faculty of Science, University of South Bohemia, České Budějovice, Czechia
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Borgerhoff Mulder M, Ross CT. Unpacking mating success and testing Bateman's principles in a human population. Proc Biol Sci 2019; 286:20191516. [PMID: 31409254 PMCID: PMC6710586 DOI: 10.1098/rspb.2019.1516] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Human marriage systems, characterized by long-term partnerships and extended windows of parental care, differ from the mating systems of pulsed or seasonally breeding non-human animals in which Bateman’s principles were originally tested. These features, paradigmatic of but not unique to humans, complicate the accurate measurement of mating success in evaluating Bateman’s three principles. Here, we unpack the concept of mating success into distinct components: number of partners, number of years partnered, the timing of partnerships, and the quality of partners. Drawing on longitudinal records of marriage and reproduction collected in a natural-fertility East African population over a 20-year period, we test and compare various models of the relationship between mating success and reproductive success (RS), and show that an accurate assessment of male and female reproductive behaviour requires consideration of all major components of mating success. Furthermore, we demonstrate that while Bateman’s third principle holds when mating success is defined in terms of years married, women’s fitness increases whereas men’s fitness decreases from an increase in the number of marriage partners, holding constant the total effective duration of marriages. We discuss these findings in terms of the distinct, sex-specific pathways through which RS can be optimized, and comment on the contribution of this approach to the broader study of sexual selection.
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Affiliation(s)
| | - Cody T Ross
- Max Planck Institute for Evolutionary Anthropology, Department of Human Behavior, Ecology and Culture, Leipzig, Germany
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Ringen EJ, Duda P, Jaeggi AV. The evolution of daily food sharing: A Bayesian phylogenetic analysis. EVOL HUM BEHAV 2019. [DOI: 10.1016/j.evolhumbehav.2019.04.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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