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Parental Investment and Sexual Selection

  • January 1972
  • In book: Sexual Selection and the Descent of Man, 1871-1971 (pp.378)
  • Publisher: Aldine, Chicago
  • Editors: Campbell, B
Authors:
Robert Trivers at Chapman University
Robert Trivers
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... Although theory and prior research on adaptive calibration suggest dyadic sexual desire may be upregulated for all people reared in unpredictable childhood ecologies, there are at least two theoretical reasons to expect that any such associations may be stronger among females compared to males. 1 First, mammalian sex and reproduction have asymmetric costs for females versus males (Trivers, 1972) such that females incur relatively greater levels of obligatory parental investment that, at a minimum, requires nine months gestation. In contrast, the minimum level of investment for males is the time it takes to contribute male gametes (e.g., sperm), which-compared to female gametes (e.g., ovum)-are plentiful and nearly immediately replenishable. ...
... Third, this work highlights the utility of integrating multiple theoretical perspectives. By integrating insights from evolutionary biology (e.g., Chisholm, 1993;Trivers, 1972) and evolutionary psychology (e.g., Li et al., 2018) with classic social psychological perspectives (e.g., Baumeister, 2000), we were able to generate the novel hypotheses tested here. Future work in this area may continue to benefit from further integration of disparate theoretical perspectives. ...
Adaptive Calibration of Dyadic Sexual Desire Is Sex Differentiated and Disrupted by Hormonal Contraceptives
Article
Full-text available
Adaptive calibration models suggest that features of people’s childhood ecologies can shape their reproductive outcomes in adulthood. Given the importance of dyadic sexual desire (i.e., desire for sex with a partner) for relationships and reproduction, we examined the extent to which people’s childhood ecologies—especially the unpredictability of those ecologies—adaptively calibrate such desire. Nevertheless, because female (versus male) sexual desire is presumed to be more sensitive to situational factors, and because hormonal contraceptives alter myriad aspects of female physiology that influence female sexual desire, we predicted that adaptive calibration of dyadic sexual desire would emerge more strongly for naturally cycling females (versus females who use hormonal contraceptives and versus males). In Study 1, a total of 630 participants (159 males, 203 naturally cycling females, and 268 females using hormonal contraceptives) completed questionnaires assessing the harshness and unpredictability of their childhood ecologies as well as their sexual desire. Consistent with predictions, childhood unpredictability (but not harshness) was positively associated with dyadic (but not solitary) sexual desire among naturally cycling females (but not among females using hormonal contraceptives nor among males). Study 2, which consisted of 736 females (307 naturally cycling females, 429 females using hormonal contraceptives), replicated this pattern of results for females. These findings add to a growing literature suggesting that the instability of people’s early childhood ecologies can adaptively calibrate their adult reproductive motivations and behaviors, including their dyadic sexual desire. Not only is the current finding among the first to show that some adaptive calibration processes may be sex differentiated, it further highlights that hormonal contraceptives, which alter the evolved reproductive physiology of females, may disrupt adaptive calibration processes (though such disruption may not be inherently negative).
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... The cascade of effects responsible for aggregate differences between females and males originates from this sex difference in investment. Because females usually invest considerably more than males in offspring, and are more limited in the quantity of offspring they can produce, they are selected to be choosier in considering partners (Bateman, 1948;Trivers, 1972). Male reproductive success is largely dependent on securing mating opportunities, through both intrasexual competition with other males and by being chosen by females in intersexual selection because of the attractiveness of their traits and displays (Darwin, 1871). ...
... Mammalian male reproductive success usually benefits more than female reproductive success from a greater number of sexual partners and the greater variation in male reproductive success compared to females heightens male competition for reproductive access to females (Bateman, 1948;Trivers, 1972). This selected for relatively higher male investment in reproductive effort at the expense of somatic maintenance and relatively higher investment in mating effort at the expense of parental effort (See Figure 2, males allocate more effort to aspects highlighted in gold, at the expense of effort for alternative aspects within sets). ...
Understanding Sex Differences in Human Mortality Rates Through Tinbergen’s Four Questions
Article
Full-text available
  • Jun 2011
Sex differences in human mortality rates emerge from a complex interaction of genetic heritage and developmental environment. Although mortality is not in itself a behavior, it is an indirect product of behavior and physiology and thus responsive to life history variation in resource allocation, behavioral tendencies, and relevant environmental conditions. The explanatory framework of Tinbergenʹs Four Questions is sufficiently powerful in generalization to promote understanding of this phenomenon. Excess male mortality is a result of a trade‐off between competitiveness and longevity. Male life history gives greater emphasis to reproductive effort at the expense of somatic effort, and mating effort at the expense of longevity compared to female life history. Men exhibit riskier behavioral patterns and greater physiological susceptibility, dying at higher rates from behavioral and most non‐behavioral causes across the lifespan. The magnitude of the sex difference in mortality in developed nations peaks when males sexually mature and enter into mating competition. Social and environmental conditions intensifying male competition for resources, status, and mates lead to increased male mortality.
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... Women's fitness is influenced by her mate's investment in her and her children especially in environments that demand biparental investment (Buss et al., 1992). The minimal investment in common offspring for human females is far larger than for males (Trivers, 1972). This has profound effects on women's willingness to mate and the adaptive problems they might be facing in case of partner infidelity. ...
Factors that Influence People’s Beliefs About Men’s and Women’s Jealousy Responses
Article
Full-text available
  • Nov 2023
This study examines what beliefs people hold about other men’s and women’s reaction to infidelity and how related these beliefs are to one’s own jealousy response and to various socio-cultural influences. This novel approach was examined in a Facebook snowball sample (N = 1213) who responded to three infidelity scenarios regarding what aspect of infidelity (emotional or sexual) they believed would make men and women more jealous and then what aspect would make themselves more jealous. The results suggest that both men and women believed men would be more upset by the sexual aspect of infidelity and that women would be more upset by the emotional aspect (i.e., falling in love). Own jealousy responses in men and women were strongly associated with beliefs about same-sex responses to infidelity and showed moderate association with beliefs about opposite-sex responses. Self-reported perceptions of cues to infidelity and knowledge from various sources about what (1) may be cues to infidelity and (2) may be typical reactions to infidelity were unrelated to beliefs about men’s and women’s jealousy responses and to own jealousy responses. We discuss whether beliefs about men’s and women’s jealousy responses may be culturally transmitted or more likely involve a dual model consisting of (a) reflection of own jealousy responses with (b) some cross-sex insights into jealousy reactions in men and women. The findings suggest that there may be evolved psychological adaptations for jealousy beliefs that extend to others of same and opposite sex.
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Copulatory Urgency: An Evolutionary Perspective of Women’s Sexual Desire
Chapter
  • Jul 2022
The interface of sexual behavior and evolutionary psychology is a rapidly growing domain, rich in psychological theories and data as well as controversies and applications. With nearly eighty chapters by leading researchers from around the world, and combining theoretical and empirical perspectives, The Cambridge Handbook of Evolutionary Perspectives on Sexual Psychology is the most comprehensive and up-to-date reference work in the field. Providing a broad yet in-depth overview of the various evolutionary principles that influence all types of sexual behaviors, the handbook takes an inclusive approach that draws on a number of disciplines and covers nonhuman and human psychology. It is an essential resource for both established researchers and students in psychology, biology, anthropology, medicine, and criminology, among other fields. Volume 3: Female Sexual Adaptations addresses theory and research focused on sexual adaptations in human females.
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Emergence of games from ecological trade-offs: longevity changes strategies for extra-pair mating in birds
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Full-text available
Each member of a breeding pair benefits if the other does more of the parental investment, so there is scope for behaviours that can be interpreted as both cooperative and competitive games between males and females. Extra-pair mating, widespread among socially monogamous birds, adds extra conflict but also potential opportunity to these social interactions. We analyse an individual-based model of a social environment with simple behavioural strategies where game-like patterns and cooperative outcomes emerge. The model focuses on three evolving traits: female propensity for extra-pair copulations and male investment in territorial behaviour and care. Male traits are reaction norms that use experienced within and extra-pair copulations as information input. We found that female extra-pair mating provided incentives for males to reduce territorial aggression and increase care for offspring. However, when adult survival was higher, male investment in care and territoriality changed from being negatively to positively correlated. This happened because longer life expectancy gave more behavioural opportunities for males, where nest desertion maximises lifetime male fitness when female extra-pair copulation is high. This outcome evolved gradually, with stable periods of intermediate extra-pair mating and low territoriality. These were punctuated by cycles of high extra-pair mating, nest desertion, reduced extra-pair mating and relapse to aggressive territoriality before a new stable phase was established. Each successive trait cycle was faster and smaller, indicating that through evolution of reaction norms, the gene pool has a long history that canalizes the evolution of behaviours, which can be interpreted as emergence and refinement of frequency-dependent games. Significance statement Most birds that mate in monogamous pairs engage in extra-pair copulations. Males of some species invest (in varying proportions) in offspring that are genetically related only to their social female. The great variability of extra-pair mating levels among different species and populations, supported by numerous field studies, indicates that social and ecological factors play a crucial role in shaping the behaviour. We analyse a computer model in which extra-pair mating evolves concurrently with male reproductive investments in territory defence and offspring care and show how common ecological trade-offs may change the social dynamics within a breeding population and lead to the emergence of complex social interactions between males, females and their neighbours.
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A Critique of Paul Seabright’s “The War of the Sexes”
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  • Sep 2014
A review of the book The war of the sexes: how conflict and cooperaton have shaped men and women from prehistory to the present by Paul Seabright (2012).
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