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How the "selfish genes" of men and women sometimes create conflict.  How monogamy, polygamy and infidelity stack up in terms of adaptive value.  Is sex addiction a real disease or just an excuse for bad behaviour?  The distinction between explanation and moral justification.  Reconciling the discrepancy between male and female instincts.

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Glenn Wilson PhD Visiting Professor of Psychology  


Alan Bennet once said he couldn’t understand the necessity for war because it pandered to instincts that were perfectly well catered for in most people’s domestic arrangements.   Physical violence is not uncommon in dating relationships. A study of American high school students revealed that 36% of girls reported experiencing violence from their partner, including being kicked, punched, scratched, slapped, choked or threatened with a weapon (De Groat, 1997). Even more astonishing was the fact that 44% of  victims stayed in the relationship. According to the Scottish Crime Survey (2000), 23% of all violent crime was domestic, most victims being women. But the frequency with which men are victims is only just being recognised. According to recent Home office statistics, one in four UK women are physically abused in the home and one in six men.   The term “sex wars” sometimes refers to battles between men as a group and women as a group. There are times when alliances are formed within gender for political purposes (e.g., the quest for equal pay, anti-rape campaigns). But most conflict occurs with others of our own gender because we are pitted against them in the struggle for mates. Here I refer to another kind of battle - those taking place between the two members of a particular couple. Outright fighting, as in domestic violence, does sometimes occur, but gene competition is generally more subtle. Gene survival dictates that a gain made by one sex (e.g., concealment of ovulation) is counteracted by an adaptation in the other (e.g., new skills for detecting fertility). This evolutionary arms race is a recurrent theme in what follows.   The seeds of conflict between men and women are rooted in the fact that their interests are seldom perfectly interlocking. For example, parental investment has led to sex differences in the preference for short-term versus long-term mating strategies. Men have a greater desire for variety in their sexual relationships, which results in them bothering women sooner and more aggressively for sex. Women typically want to wait until there is evidence of emotional involvement in the relationship. Clearly, the desires of  the two sexes cannot simultaneously be satisfied. American comedian Max Kauffmann quipped: “She was a lovely girl. Our courtship was fast and furious - I was fast and she was furious”.   An internet survey of 1743 people who had one-night stands revealed that 80% of men had positive feelings about it afterwards, compared to only 54% of women (Campbell, 2008). While the men usually reported feelings of satisfaction, contentment and increased confidence, women often felt used and regretful.   Men seem to have evolved a tendency to infer sexual interest in women where none exists (DeSousa et al, 1992). A typical experiment is to film a friendly encounter between a man and a woman and ask viewers to rate the extent to which each is being seductive or flirtatious. Men are more likely than women to perceive sexual intent on the part of a friendly, smiling person of the opposite sex. The reverse is more likely to be the truth of the matter - men being more likely to have sex on the brain than women. This is the more adaptive error for a man to make, since it might occasionally lead to sex; failure to recognise sexual interest when it does exist results in a missed opportunity. However, women (on their own admission) sometimes use flirtation as a tactic to get what they want from men without any intention of having sex (Buss, 1999). Putting these two tendencies together it easy to see how men might feel they are being “teased” , with resentment being the result.   The flip-side of insincere female flirtation is the tendency for some men to feign love in order to get a woman into bed. A study of American college students found that 97% of women were victims of this strategy, while 71% of men admitted using it (Buss, 1994). Again, the evolutionary origins are clear – ancestral women risked being “left with the baby”, while the casual male moved on. Not surprisingly, women guard against such deception by requiring greater courtship effort, buying time in which to assess the intentions of their suitor.   Men who tire of such delays and hurdles might choose to pay upfront for their sexual novelty, which is why “prostitution is the oldest profession” and why there are more protitutes than gigolos. One handsome Hollywood star, asked why he used call girls supplied by Madam Heidi Fleiss when he could have virtually any woman he wanted, replied: “You misunderstand, I don’t pay these women to have sex with me, I pay them to go away afterwards.” Sex without love is seldom sought by women   Sexual harassment in the workplace also reflects evolved differences between men and women. Women more readily take offense at sexual advances than men, and young, sexually attractive and single women are disproportionately targeted. However, the status of a harasser is a major factor. Advances are much less welcome coming from married men and those of low occupational status. They are also less well received when perceived as coercive and sexual rather than romantic. Men seldom protest sexual suggestions and, of course, there are some women who gain material advantages in the workplace through casual mating (Buss, 1999).   An extreme form of harassment is the use of force of obtain sex. Evolutionary psychologists have proposed that, although rape is repugnant to the victim and risky to the rapist, it could be “adaptive” in that a man who “steals” sex because he cannot get consent from women gives his genes at least a chance of replication.(Thornhill & Thornhill,  1992). In other words, the choice of the loser male may be force or genetic extinction. The evidence is equivocal: rapists are usually high in libido, impulsive and brutal. They are also likely to have a record of other types of property crime. However, they are not usually deprived of legitimate sexual activity.   Women who are raped are apparently more likely to get pregnant as a result of that event than those having a brief consensual encounter (Gottschall & Gottschall, 2002). The reasons for this are not certain. They include several possibilities: (1) Victims targeted by rapists are especially fertile at the time, being young, attractive and mid-cycle. (2) The trauma of rape may induce ovulation, as it does in certain animals (3) The ejaculate of a rapist may be more potent or better received. The so-called “sexy son” hypothesis is that the sperm of rapists is by some mechanism favoured by their victims because it might produce sons that are genetically more rampant than those of a consenting partner (Baker & Bellis, 1995). This idea is controversial because it implies that women unconsciously “conspire” with the rapist. Interestingly, though, many women who report date-rape continue to date their abuser.   A sense in which women might “conspire” with sexual marauders concerns the signals that they emit when fertile. Research shows that women are more flirtatious when ovulating, exposing more flesh and dancing more provocatively. This is especially so when they have a long-term partner (Grammer et al, 2005). They are also more interested in sex, buy sexier clothing, are more easily aroused and more prone to infidelity (Bullivant et al, 2004; Baker & Bellis, 1995; Haselton et al, 2007; Durante et al, 2011).      There is no suggestion that these mechanisms are conscious. Consider the concept of pheromone wars. Men secrete androstenone which has the effect of repelling other men, and women, except for those that are ovulating (who seem to be attracted by it). In retaliation, women secrete copulins, which cause males to lose the ability to discriminate against unattractive women. Thus pheromones appear to be engaged in an evolutionary arms race that is played out largely below our threshold of awareness (Grammer et al, 2005).   The cold brutality of genetic conflict is nowhere more striking than in the statistics of infanticide. It is well known that lions kill the offspring of a lioness that were fathered by another lion before re-impregnating her themselves. People are loath to imagine that humans harbour such instincts. Yet in some tribal societies men insist that a child be killed if they suspect it is not their own. In Western society, a preschool child is between 40 and 100 times more likely to be murdered by a step-parent than by a natural parent (Daly & Wilson, 1988) and most mothers who kill their own child are in the thrall of a new male partner. Once again, evolutionary psychology reminds us of our primitive, basic nature, however much we strive to deny and suppress it.   Infidelity is another obvious battleground in the evolutionary arms race. Men gain genetic advantage by having multiple partners and, in cultures where males are politically dominant, polygyny is common. But women also have motives for infidelity. It provides “fertility insurance”, in case the regular partner is infertile for any reason, or they may gain fitter genes for their offspring than those of their regular partner without sacrificing stable support. Women tend to more exploratory when they are most fertile, e.g., when young and mid-cycle (Birkhead, 2000; Baker & Oram, 2000).   That humans are not naturally monogamous is indicated by comparisons with other apes with respect to the relative size of the males and females and the size of their testicles relative to body weight. In monogamous species males and females are about the same size but human males are bigger than the female. In promiscuous apes, like chimpanzees, the testicles are large relative to body size. In this respect, human males are more like chimps than other great apes. Baker & Bellis (1995) argue that large testicles are necessary where the sperm of a male may have to compete with that of other males. Sheer quantity is a good start but human sperm may be specialised, such that some are egg-getters while others are kamikazes, whose role is to destroy the sperm of other males that might be competing in the female reproductive tract. In support of the possible need for human sperm to be competitive, Baker & Bellis cite a survey revealing that 30% of sexually active women admit to having sex with different men within a 24-hour time frame.   Other strategies also have advantages. Some men protect harems of females, like gorillas. Some use coercive sex, like orang-utans. Still others successfully pass on their genes by long-term bonding with a partner whom they help to raise a limited number of well-cared for offspring (more like gibbons). What is unusual about humans is that these strategies all exist in parallel, each with some potential adaptive value.   Jealousy is the emotion felt when a partner feels threatened by a rival. Men and women experience jealousy to a similar degree but it takes different forms (Buss, 1999). Where men are concerned, jealousy focuses on sexual contact, particularly the act of penetration (raising the fear of cuckoldry – the risk of expending resources on offspring not carrying their own genes). Women are more threatened by signs that their partner is becoming emotionally involved with the rival (with potential loss of the relationship and its attendant resources).   Jealousy would have no adaptive benefit if it did not lead to behavioural changes and those most relevant are called mate retention behaviours. They range from vigilance to violence (Buss & Shackelford, 1997) but some are more typical of men and others favoured by women. Men are more likely to: (1) display resources (e.g. expensive gifts, (2) conceal their mate (e.g. not taking them to a party where other men might chat her up), (3) submit to them (grovel and plead) and (4) threaten punishment or violence against rivals. Women are more likely to: (1) enhance their appearance (using make-up, wearing new clothes) and (2) deliberately induce jealousy in their partners (e.g., showing an interest in a rival). Predictably, the vigour with which mate retention behaviours are pursued relates to the mate value of the partner (physical attractiveness of a female partner and the income/social status of the man being most important), as well as the perceived likelihood of them straying.   Although it seems paradoxical, insulting and belittling the partner may function as a mate retention strategy. Verbal, and even physical, abuse can impair the self-worth of the partner such that they feel they have no options (“who else would want me”?) (McKibbin et al, 2007). This may account for the fact that so many women stay in abusive relationships.   So far this discussion has been along the lines of cold logic with no mention of morality, recalling Darwin’s famous description of nature as “red in tooth and claw”. Many of the tactics and strategies evolved by men and women to favour the survival of their selfish genes are not pretty or admirable. Evolutionary instincts help to explain various behaviour pattern but this does not endorse them. “Adaptive” should not be taken to mean “justifiable”. Knowing that a baby is more likely to be abused by a step-parent than biological parent does not make the killing “baby-P” any less horrific. If a man kills his wife on catching her in bed with a rival it may be understandable as a “crime of passion” but that does not excuse it. We are not total slaves to our instincts. Human civilisation depends upon restraint. Morality is the prescription for this restraint and sometimes it needs backing up with the threat of severe penalties. Nothing in evolutionary psychology should be taken as acceptance, let alone promotion, of bestial behaviour.   The guidelines for morality were traditionally enshrined in religious scriptures, like the Ten Commandments or Sharia law. These can become dated and inappropriate, even though some (fundamentalists) cling to them tenaciously. More recently, we have sought to medicalise the behaviours we find troublesome.   Take sex addiction. This is rather a misnomer since “addiction” normally refers to the chemical hijacking of brain circuits evolved to reward behaviour that is of survival benefit (notably sex). However, a strong sex drive can be disruptive to family life or lead to charges of harassment, hence some of kind of training in self-control might be called for. Some men undertake “therapy” in the hope of repairing their marriage, their arm being firmly twisted up their back by an angry wife.   The danger is that by attaching medical labels to what is really just bad behaviour we give the “afflicted” individual an excuse which “lets them off the hook”  It helps them to evade responsibility for their actions, while adding nothing of scientific value. Pharmaceutical companies then cash in by developing drugs aimed at these newly identified “disorders” and insurance companies reinforce the fiction by demanding a “diagnosis” before shelling out for treatment. In some ways, the religious concept of “sin” was more apt. What we are talking about is immoral behaviour, not a medical illness.   What can be done to bring about peace in the sex wars? Perhaps ultimately very little because the seeds of conflict are deep-rooted. So long as men and women have different desires difficulties are bound to arise. But the first step towards peace is understanding the causes of conflict and in this regard evolutionary psychology can be enlightening. If principles above are properly understood we are in a better position to engage with the point of view of the opposite sex. Adopting the ostrich stance is not helpful. And as with international diplomacy, the next step toward harmony, after the recognition of people’s natural differences, is tolerance of them. Finally, we need to arrive at negotiated compromises that openly take account of each other’s needs.   One thing is for sure, we cannot live apart from each other. Men and women need each other because of, rather than despite, our differences. As Henry Kissinger once said: “Nobody will ever win the battle of the sexes – there’s too much fraternising with the enemy”.     References Baker, R.R. & Bellis, M. (1995) Human sperm competition: Copulation, Masturbation and Infidelity, London: Chapman & Hall. Baker, R.R. & Oram, E. (2000) Baby Wars: Dynamics of Family Conflict. New York: Basic Books. Birkhead, T. (2000) Promiscuity: An Evolutionary History of Sperm Competition. London: Faber & Faber. Bullivant, S.B. et al (2004) Women’s sexual experience during the menstrual cycle: Identification of the sexual phase by non-invasive measurement of luteinising  hormone. Journal of Sexual Research, 41, 82-93. Buss, D.M. (1994) The strategies of human mating. American Scientist, 82, 238-249. Buss, D.M. (1999) Evolutionary Psychology. Boston: Allyn & Bacon. Buss, D.M. & Shackelford, T.K. (1997) From vigilance to violence: Mate retention tactics in married couples. Journal of Personality and Social Psychology, 72, 346-361. Campbell, A. (2008) The morning after the night before: Affective reactions to one-night stands among mated and unmated women and men. Human Nature, 19, 157-173. Daly, M. & Wilson, M. (1988) Homocide. NY: Aldine. DeGroat, B.(1997) Dating violence differs for teenage boys, girls. The University Record, April 1, p.15). DeSousa, E.R., Pierce, T., Zanelli, J.C. & Hutz, C. (1992) Perceived sexual intent in the United States and Brazil as a function of nature of encounter, subjects’ nationality and gender. Journal of Sex Reseach, 29, 251-260. Durante, K.M., et al (2011) Ovulation, female competition and product choice: Hormonal influences on consumer behaviour. Journal of Consumer Research, April 2011 (online). Gottschall, J.A. & Gottschall, T.A. (2002) Are per-incident rape-pregancy rates higher than per-incident consensual rates? Human Nature, 14, 1-20. Grammer, K., Fink, B. & Neave, N. (2005) Human pheromones and sexual attraction. European Journal of Obstetrics & Gynecology and Reproductive Biology, 118, 135-142. Grammer, K., Renninger, L. & Fischer, B. (2005) Disco clothing, female sexual motivation and relationship status: Is she dressed to impress? Journal of Sex Research, 41, 66-74. Haselton, M.G., Mortezai, M. et al (2007) Ovulatory shifts in human female ornamentation: Near ovulation women dress to impress. Hormones and Behaviour, 51, 40-45. McKibbon, W.F., Goetz, A.T. et al (2007) Why do men insult their intimate partners. Personality and Individual Differences, 43, 231-241. Thornhill, R. & Thornhill, N. (1992) The  evolutionary psychology of men’s coercive sexuality. Behavioural and Brain Sciences, 15, 363-421.


©Professor Glenn Wilson, Gresham College 2011

This event was on Tue, 22 Feb 2011

Dr Glenn D. Wilson

Dr Glenn D Wilson

Visiting Professor of Psychology

Glenn D. Wilson is one of Britain's best-known psychologists. He has appeared on numerous television and radio programmes and has published more than 150 scientific...

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