Female Infidelity and Paternal Uncertainty – Evolutionary Perspectives on Male Anti-Cuckoldry Tactics

I finished this book yesterday. Below I have posted my goodreads review:

“A couple of chapters were really nice, but the authors repeat themselves *a lot* throughout the book and some chapters are really weak. I was probably at three stars after approximately 100 pages, but the book in my opinion lost steam after that. A couple of chapters are in my opinion really poor – basically they’re just a jumble of data-poor theorizing which is most likely just plain wrong. A main hypothesis presented in one of the chapters is frankly blatantly at odds with a lot of other evidence, some of which is even covered earlier in the same work, but the authors don’t even mention this in the coverage.

I don’t regret reading the book, but it’s not that great.”

…

Let’s say you have a book where Hrdy’s idea that it’s long been in the interest of human females to confuse paternity by various means, e.g. through extra-pair copulations, because such behaviour reduces the risk of infanticide (I’ve talked about these things before here on the blog, if you’re unfamiliar with this work and haven’t read my posts on the topics see for example this post) is covered, and where various other reasons why females may choose to engage in extra-pair copulations (e.g. ‘genetic benefits’) are also covered. Let’s say that in another, problematic, chapter of said book, a theory is proposed that ‘unfamiliar sperm’ (sperm from an individual the female has not had regular sex with before) leading to pregnancy is more likely to lead to preeclampsia in a female, a pregnancy complication which untreated will often lead to the abortion of the fetus. Let’s say the authors claim in that problematic chapter that the reason why females are more likely to develop preeclampsia in case of a pregnancy involving unfamiliar sperm is that such a pregnancy is likely to be a result of rape, and that the physiological mechanism leading to the pregnancy complication is an evolved strategy on part of the female, aimed at enabling her to exercise (post-copulatory) mate choice and reduce the negative fitness consequences of the rape. Let’s say the authors of the preeclampsia chapter/theory don’t talk at all about e.g. genetic benefits derived from extra-pair copulations which are not caused by rape but are engaged in willingly by the female because it’s in her reproductive interests to engage in them, and that the presumably common evolutionary female strategy of finding a semi-decent provider male as a long-term partner while also occasionally sleeping around with high-quality males (and low quality males – but only when not fertile (e.g. when pregnant…)) and have their children without the provider male knowing about it is not even mentioned. Assume the authors of the chapter seem to assume that getting a child by a male with unfamiliar sperm is always a bad idea.

Yeah, the above is what happened in this book, and it’s part of why it only gets two stars. These people are way too busy theorizing, and that specific theory is really poor – or at least the coverage of it was, as they don’t address the obvious issues which people reading the other chapters wouldn’t even have a hard time spotting. Kappeler et al. is a much better book, and it turns out that there was much less new stuff in this book than I’d thought – a lot of ‘the good stuff’ is also covered there.

It doesn’t help that many of the authors are systematically overestimating the extra-pair paternity rate by relying on samples/studies which are obviously deeply suspect due to selection bias. Not all of them goes overboard and claim the number is 10% or something like that, but many of them do – ‘the number is between 1-30%, with best estimates around 10%’ is a conclusion drawn in at least a couple of chapters. This is wrong. Only one contributor talking about these numbers come to the conclusion that the average number is likely to have been less than 5% in an evolutionary context (“Only very tentative conclusions about typical EPP [extra-pair paternity] rates throughout recent human history (e.g. in the past 50 000 years) can be drawn […] It seems reasonable to suggest that rates have typically been less than 10% and perhaps in most cases less than 5%. It also seems reasonable to suggest that they have probably also been variable across time and place, with some populations characterized by rates of 10% or higher.”). An idea worth mentioning in this context is that human behaviour can easily have been dramatically impacted by things which rarely happen now, because the reason why those things may be rare may well be that a lot of behaviour is aimed towards making sure it is rare and stays rare – this idea should be well known to people familiar with Hrdy’s thesis, and it also to me seems to apply to cuckoldry; cuckoldry may happen relatively infrequently, but perhaps the reason for this is that human males with female partners are really careful not to allow their partners to sleep around quite as much as their genetic code might like them to do. I mentioned in the coverage of Kappeler et al. that female sexual preferences change over the course of her menstrual cycle – they also talk about this in this book, but a related observation also made in the book is that males seem to be more vigilant and seem to intensify their level of mate guarding when their partner is ovulating. There’s probably a lot of stuff which goes on ‘behind the scenes’ which we humans are not aware of. Human behaviour is really complicated.

All these things said, there’s some really nice stuff in the book as well. The basic idea behind much of the coverage is that whereas females always know that their children are their children, males can never know for sure – and in a context where males may derive a fitness benefit from contributing to their offspring and a fitness loss by contributing to another male’s child, this uncertainty is highly relevant for how they might choose to behave in many contexts related to partnership dynamics. Many different aspects of the behaviour of human males is to some extent directed towards minimizing the risk of getting cuckolded and/or the risk of a partner in whom they have invested leaving him. They may choose to hide the female partner from competitors e.g. by monopolizing her time or by using violence to keep her from interacting with male competitors, they may signal to competitors that she is taken and/or perhaps that it may be costly to try to have sex with her (threats to other males, violence directed towards the competitor rather than the partner), they may try to isolate her socially by badmouthing her to potential competitors (e.g. male friends and acquaintances). On a more positive note males may also choose to do ‘nice things’ to keep the partner from leaving him, like ‘giving in to sexual requests’ and ‘performing sexual favors to keep her around’ (in at least one study, “men partnered to women who [were] more likely to be sexually unfaithful [were] also more likely to perform sexual inducements to retain their partners” – but before women reading this conclude that their incentives may look rather different from what they thought they did, it’s probably worth noting that the risk of abuse also goes up when the male thinks the partner might be unfaithful (see below)). If the first anti-cuckold approach, the mate-guarding strategy of trying to keep her from having sex with others, fails, then the male has additional options – one conceptualization in the book splits the strategy choices up into three groups; mate-guarding strategies, intra-vaginal strategies and post-partum strategies (in another chapter they distinguish among “preventative tactics, designed to minimize female infidelity; sperm-competition tactics, designed to minimize conception in the event of female infidelity; and differential paternal investment” – but the overall picture is reasonably similar). Intra-vaginal strategies relate to sperm competition and for example more specifically relate to e.g. the observation that a male may try to minimize the risk of being cuckolded after having been separated from the partner by having sex with the partner soon after they meet up again. A male may also increase the amount of sperm deposited during intercourse in such a context, compared to normal, and ‘sexual mechanics’ may also change as a function of cuckoldry risk (deeper thrusts and longer duration of sex if they’ve been separated for a while). There are five chapters on this stuff in the book, but I’ve limited coverage of this stuff because I don’t think it’s particularly interesting. Post-partum strategies naturally relate to strategies employed after the child has been born. Here the father may observe the child after it’s been born and then try to figure out if it looks like him/his family, and then adjust investment in the child based on how certain he is that he’s actually the father:

“There is growing evidence that human males are […] affected by […] evolutionary pressures to invest in offspring as a function of paternal certainty”, and “Burch and Gallup (2000) have shown that males spend less time with, invest fewer resources in, and are more likely to abuse ostensibly unrelated children than children they assume to be their genetic offspring. They also found that the less a male thinks a child (unrelated or genetic) looks like him, the worse he treats the child and the worse he views the relationship with that child.”

It’s worth mentioning that dividing the strategy set up into three, and exactly three, overall categories seem to me slightly artificial, also because some relevant behaviours may not fit very well into any of them; to take an example, “There is growing evidence that males who question their partner’s fidelity show an increase in spouse abuse during pregnancy, and the abuse is often directed toward the female’s abdomen” – this behavioural pattern relates to none of the three strategy categories mentioned, but also seems ‘relevant’. In general it’s important to observe that employment of a specific type of tactic does not necessarily preclude the employment of other tactics as well – as pointed out in the book:

“A male’s best strategy is to prevent female infidelity and, if he is unsuccessful in preventing female infidelity, he would benefit by attempting to prevent conception by a rival male. If he is unsuccessful in preventing conception by a rival male, he would benefit by adjusting paternal effort according to available paternity cues. The performance of one tactic does not necessitate the neglect of another tactic; indeed, a reproductively wise strategy would be to perform all three categories of anti-cuckoldry tactics”

There’s a lot of food for thought in the book. I’ve included some more detailed observations from the book below – in particular I’ve added some stuff closely related to what I believe people might normally term ‘red flags’ or similar in a relationship context. I’d say that enough research has been done on this kind of stuff for it to make a lot of sense for women to read some of it – in light of the evidence, there are certain types of male behaviours which should most definitely be considered strong warning signs that it may be a bad idea to engage with this individual. (I was annoyed that the book only dealt with male abuse, as there are quite a few female abusers as well, but I can’t really fault the authors for limiting coverage to male behaviours).

…

“Paternal investment in humans and many other species is facultatively expressed: it often benefits offspring but is not always necessary for their survival and thus the quantity and quality of human paternal investment often varies with proximate conditions […] The facultative expression of male parenting reflects the […] cost–benefit trade-offs as these relate to the current social and ecological contexts in which the male is situated. The degree of male investment (1) increases with increases in the likelihood that investment will be provided to his own offspring (i.e. paternity certainty), (2) increases when investment increases the survival and later reproductive prospects of offspring, and (3) decreases when there are opportunities to mate with multiple females. […] the conditional benefits of paternal investment in these species results in simultaneous cost–benefit trade-offs in females. Sometimes it is in the females’ best interest (e.g. when paired with an unhealthy male) to cuckold their partner and mate with higher-quality males […] As a result, women must balance the costs of reduced paternal investment or male retaliation against the benefits of cuckoldry; that is, having their children sired by a more fit man while having their social partner assist in the rearing of these children.”

“In several large but unrepresentative samples, 20–25% of adult women reported having had at least one extra-pair sexual relationship during their marriage […] Using a nationally representative sample in the USA, Wiederman (1997) found that 12% of adult women reported at least one extra-pair sexual relationship during their marriage, and about 2% reported such a relationship during the past 12 months; Treas and Giesen (2000) found similar percentages for another nationally representative sample. These may be underestimates, given that people are reluctant to admit to extra-pair relationships. In any case, the results indicate that some women develop simultaneous and multiple opposite-sex relationships, many of which become sexual and are unknown to their social partner […] The dynamics of these extra-pair relationships are likely to involve a mix of implicit (i.e. unconscious) and explicit (i.e. conscious) psychological processes (e.g. attention to symmetric facial features) and social strategies. […] the finding that attraction to extra-pair partners is influenced by hormonal fluctuations points to the importance of implicit mechanisms. […] The emerging picture is one in which women appear to have an evolved sensitivity to the proximate cues of men’s fitness, a sensitivity that largely operates automatically and implicitly and peaks around the time women ovulate. The implicit operation of these mechanisms enables women to assess the fitness of potential extra-pair partners without a full awareness that they are doing so. In this way, women are psychologically and socially attentive to the relationship with their primary partner and most of the time have no explicit motive to cuckold this partner. If their social partners monitor for indications of attraction to extra-pair men, which they often do […], then these cues are only emitted during a short time frame. Moreover, given that attraction to a potential extra-pair partner is influenced by hormonal mechanisms, often combined with some level of pre-existing and non-sexual emotional intimacy with the extra-pair male […], many of these women may have no intention of an extra-pair sexual relationship before it is initiated. Under these conditions, the dynamics of cuckoldry may involve some level of self deception on women’s part, a mechanism that facilitates their ability to keep the extra-pair relationship hidden from their social partners. […] As with women, men’s anti-cuckoldry biases almost certainly involve a mix of implicit processes and explicit behavioral strategies that can be directed toward their mates, toward potential rivals, and toward the evaluation of the likely paternity of children born to their partners”

“Males have evolved psychological adaptations that produce mate guarding and jealousy […] to reduce or to prevent a mate from being inseminated by another male. Recent evidence suggests that males maximize the utility of their mateguarding strategies by implementing them at ovulation, a key reproductive time in a female’s menstrual cycle […]. Further, jealousy appears to fluctuate with a man’s mate value and, hence, risk of cuckoldry. Brown and Moore (2003), for example, found that males who were less symmetrical were significantly more jealous. These and other data suggest that jealousy has evolved as a means by which males can attempt to deter extra-pair copulations […] When triggered, jealousy often results in a variety of behavioral responses, including male-on-female aggression […], divorce […], the monitoring and attempted control of the social and sexual behavior of their partners […], enhancement of their attractiveness as a mate […], and the monitoring of and aggression toward actual or perceived sexual rivals […]. In total, these behaviors encompass tactics that function to ensure, through coercion or enticement, that their reproductive investment and that of their mate is directed toward the man’s biological children. […] One of the more common behavioral responses to relationship jealousy is mate guarding. For men this involves reducing their partner’s opportunity to mate with other men.”

“Cuckoldry is a reproductive cost inflicted on a man by a woman’s sexual infidelity or temporary defection from her regular long-term relationship. Ancestral men also would have incurred reproductive costs by a long-term partner’s permanent defection from the relationship. These costs include loss of the time, effort, and resources the man has spent attracting his partner, the potential misdirection of his resources to a rival’s offspring, and the loss of his mate’s investment in offspring he may have had with her in the future […] Expressions of male sexual jealousy historically may have been functional in deterring rivals from mate poaching […] and deterring a mate from a sexual infidelity or outright departure from the relationship […] Buss (1988) categorized the behavioral output of jealousy into different ‘‘mate-retention’’ tactics, ranging from vigilance over a partner’s whereabouts to violence against rivals […] Performance of these tactics is assessed by the Mate Retention Inventory (MRI[)] […] Buss’s taxonomy (1988) partitioned the tactics into two general categories: intersexual manipulations and intrasexual manipulations. Intersexual manipulations include behaviors directed toward one’s partner, and intrasexual manipulations include behaviors directed toward same-sex rivals. Intersexual manipulations include direct guarding, negative inducements, and positive inducements. Intrasexual manipulations include public signals of possession. […] Unfortunately, little is known about which specific acts and tactics of men’s mate-retention efforts are linked with violence. The primary exception is the study by Wilson, Johnson, and Daly (1995), which identified several predictors of partner violence – notably, verbal derogation of the mate and attempts at sequestration such as limiting access to family, friends, and income.”

“Tactics within the direct guarding category of the MRI include vigilance, concealment of mate, and monopolization of time. An exemplary act for each tactic is, respectively, ‘‘He dropped by unexpectedly to see what she was doing,’’ ‘‘He refused to introduce her to his same-sex friends,’’ and ‘‘He monopolized her time at the social gathering.’’ Each of these tactics implicates what Wilson and Daly (1992) term ‘‘male sexual proprietariness,’’ which refers to the sense of entitlement men sometimes feel that they have over their partners […] Wilson et al. (1995) demonstrated that violence against women is linked closely to their partners’ autonomy-limiting behaviors. Women who affirmed items such as ‘‘He is jealous and doesn’t want you to talk to other men,’’ were more than twice as likely to have experienced serious violence by their partners.” [What was the base rate? I find myself asking. But it’s still relevant knowledge.] […] Not all mate-retention tactics are expected to predict positively violence toward partners. Some of these tactics include behaviors that are not in conflict with a romantic partner’s interests and, indeed, may be encouraged and welcomed by a partner […] Holding his partner’s hand in public, for example, may signal to a woman her partner’s commitment and devotion to her. […] Tactics within the public signals of possession category include verbal possession signals (e.g. ‘‘He mentioned to other males that she was taken’’), physical possession signals (e.g. ‘‘He held her hand when other guys were around’’), and possessive ornamentation (e.g. ‘‘He hung up a picture of her so others would know she was taken’’).”

“The current studies examined how mate-retention tactics are related to violence in romantic relationships, using the reports of independent samples of several hundred men and women in committed, romantic relationships […], and using the reports of 107 married men and women […] With few exceptions, we found the same pattern of results using three independent samples. Moreover, these samples were not just independent, but provided different perspectives (the male perpetrator’s, the female victim’s, and a combination of the two) on the same behaviors – men’s mate-retention behaviors and men’s violence against their partners. We identified overlap between the best predictors of violence across the studies. For example, men’s use of emotional manipulation, monopolization of time, and punish mate’s infidelity threat are among the best predictors of female-directed violence, according to independent reports provided by men and women, and according to reports provided by husbands and their wives. The three perspectives also converged on which tactics are the weakest predictors of relationship violence. For example, love and care and resource display are among the weakest predictors of female-directed violence. […] The tactic of emotional manipulation was the highest-ranking predictor of violence in romantic relationships in study 1, and the second highest-ranking predictor in studies 2 and 3. The items that comprise the emotional manipulation tactic include, ‘‘He told her he would ‘die’ if she ever left,’’ and ‘‘He pleaded that he could not live without her.’’ Such acts seem far removed from those that might presage violence. […] Monopolization of time also ranked as a strong predictor of violence across the three studies. Example acts included in this tactic are ‘‘He spent all his free time with her so that she could not meet anyone else’’ and ‘‘He would not let her go out without him.’’ […] The acts ‘‘Dropped by unexpectedly to see what my partner was doing’’ and ‘‘Called to make sure my partner was where she said she would be’’ are the third and fifth highest-ranking predictors of violence, respectively. These acts are included in the tactic of vigilance, which is the highest-ranking tactic-level predictor of violence in study 3. Given that (1) two of the top five actlevel predictors of violence are acts of vigilance, (2) the numerically best tactic-level predictor of violence is vigilance, and (3) seven of the nine acts included within the vigilance tactic are correlated significantly with violence […], a man’s vigilance over his partner’s whereabouts is likely to be a key signal of his partner-directed violence. […] Wilson et al. (1995) found that 40% of women who affirmed the statement ‘‘He insists on knowing who you are with and where you are at all times’’ reported experiencing serious violence at the hands of their husbands.”

“Relative to women’s reports of their partners’ behavior, men self-reported more frequent use of intersexual negative inducements, positive inducements, and controlling behavior. Although not anticipated, the sex difference in reported frequency of controlling behaviors is not surprising upon examination of the acts included in the CBI [Controlling Behavior Index]. More than half of the acts do not require the woman’s physical presence or knowledge, for example ‘‘Deliberately keep her short of money’’ and ‘‘Check her movements.’’ In addition, such acts might be more effective if the woman is not aware of their occurrence. […] Increased effort devoted to mate retention is predicted to occur when the adaptive problems it was designed to solve are most likely to be encountered – when a mate is particularly desirable, when there exist mate poachers, when there is a mate-value discrepancy, and when the partner displays cues to infidelity or defection”

“Although sometimes referred to as marital rape, spouse rape, or wife rape,we use the term forced in-pair copulation (FIPC) to refer to the forceful act of sexual intercourse by a man against his partner’s will. […] FIPC is not performed randomly […] FIPC reliably occurs immediately after extra-pair copulations, intrusions by rival males, and female absence in many species of waterfowl […] and other avian species […] FIPC in humans often follow[s] accusations of female infidelity”