HeterosexualityHuman heterosexuality is unique in the animal kingdom - commonly cited unique features are the menopause, cryptic ovulation, female orgasm, permanent breasts, and parental pair formation. It is argued that this uniqueness arose, ultimately, from our coevolution with social knowledge and social groups.
The Structure of Human Heterosexuality
9.1 The Aims of this Chapter
9.2 The Uniqueness of Women
9.3 The Menopause
9.4 The Purpose of Sex - Family Pair Formation
9.5 Breaking the Sexual Deal
9.6 Game Theory, Heterosexuality and Parental Cooperation
9.7 Evolution and Family Parenting
9.8 The Emotional Origins of Family Parenting
9.9 Bioepistemic Evolution and Family Parenting
9.10 Why Men and Women are Attracted to Different Things
9.11 Forms of Power in a Family Group
9.12 Why Different People are Attracted to Different Things
9.13 Epistemology, Bioepistemic Evolution, Sexuality and Family Relations
9.14 Sexuality and Communication
9.15 A Classification of Social Pairs
9.16 Mother and Baby
Most of the traits that make humans unique are linked to our social organisation and the level3 knowledge (social knowledge) that underpins it. So far we have discussed the knowledge processing organs, the brain, the vocal system and hands, that enable us to manipulate knowledge and the structure of irrationality that, in part, guides what we do with it. If Darwin's ideas on evolution by sexual selection are correct, human sexuality will also have been altered by the growth of level3 knowledge, creating unique sexual characteristics that arise from social evolution. Hence, this chapter and the next will review and interpret human sexual traits, concentrating on heterosexuality.
Sexuality can be divided into three aspects. Firstly, the biology of sex, that is the anatomical structure and physiological functioning of sex organs that are under genetic control. Unique aspects human sexual biology will be reviewed.
Secondly, sexuality concerns the people, things or situations that induce a sexual response. These inducers are observed at level2 and somehow affect the brain to produce sexual excitement. Humans respond sexually to a wide range of stimuli, and are very heterogeneous in this property, different people responding to different stimuli. There is no general agreement as to whether forms of sexuality are learned or genetic but evolution by sexual selection indicates that human behavioural heterogeneity, itself arising from group selection, should be matched by heterogeneity in sexuality, implying that many sexualities will have a genetic origin.
Thirdly, there are learned behaviours associated with sexual discourse. Such things cover a wide range, from presenting a rose to one's lady and her choice of clothing and perfume, to knowing which bars are frequented by members of the homosexual community. A person's particular behaviours illuminate their sexuality but the picture projected is not a clear one. This may be because one sexuality can lead to a range of behavioural choices, because one person can possess more than one sexuality or both. We will not be concerned with learned behaviours unless they appear to illuminate an underlying sexuality.
Given the widespread interest in sex, these chapters may turn out to be the most widely read parts of this work, which does not mean they are academically the best. This chapter will be concerned with heterosexuality and some of the striking differences between normal human sexual biology and that of other mammals. Chapter 10 will concern sexual "deviance", forms of sexual behaviour not generally regarded as normal, though the meaning of "normal" is unclear, given the unusual and heterogeneous nature of human sexuality. Humour also has parallels with sex but will be deferred to chapter 11.
Humans have an unusual heterosexuality and a sexual biology that adapted to adult mating pair formation. Its biological role is child rearing and the transfer of knowledge from one generation to the next. In other words, social knowledge makes long term pair formation desirable for child rearing and education; evolution has achieved these human pairs by changes in our heterosexual characteristics that encourage men and women to form and maintain them. This chapter will express that conclusion using original terminology but the conclusion itself is by no means original and fairly standard among evolutionary biologists. These are well- known arguments, rephrased and reemphasised to reflect this work's aims and terminology.
The next chapter will offer a similar arguments about sexual deviance, namely that the presence of knowledge creates evolutionary arrows producing such traits as homosexuality and sadomasochism. That interpretation does seem original and one merit of the present terminology is that it makes the comparisons much easier.
The general information in this chapter derives from Ridley (1993), Gould and Gould (1996), Huxley (1942), Haeberle (1983) and the Kinsey Reports.
To begin with, here again is the list of some unique, human, sexual characteristics.
Female mammary gland development.
Female sexual receptiveness during infertile periods.
Human males are attracted to females outside their fertile periods.
Differential reproduction, that is, large numbers of people choose not to reproduce.
Adult humans can survive well beyond their reproductive years and are often group leaders at an essentially infertile time of life.
The most obviously unique features of human sexual biology, are shown by women, breasts (permanently developed mammary glands), cryptic ovulation, the menopause and orgasm. This section will consider the first two traits, alongside the phenomenon of permanent sexual receptivity, a trait of both men and women. Section 9.3 will discuss the menopause.
Menstruation occurs in virtually all mammals, though its timing varies. In women, the menstrual cycle lasts for twenty eight days, with days normally counted from the onset of bleeding. Ovulation occurs on about day fourteen, when the ovaries release an egg which passes down the fallopian tube toward the uterus, being helped on its way by peristaltic waves on the tube wall and hairlike cilia of the cells that line it. If sexual intercourse has taken place recently, the egg may meet a male sperm, and the two can fuse to produce a fertilised egg. The life expectancy of egg and sperm is such that a woman can become pregnant following intercourse during the two weeks surrounding ovulation, that is from days seven to twenty one of her period. She is most likely to become pregnant if intercourse takes place during ovulation itself.
During the period leading up to ovulation, the endometrium, the wall of the uterus, thickens and becomes ready to implant a fertilised egg. If no egg implants, the endometrium breaks down to be discharged as the bleeding that begins a period. An implanted embryo releases hormones that stabilise the endometrium and it becomes a substrate one which the placenta grows as the embryo develops.
In most mammals it is obvious when females ovulate. A human observer may see nothing but the male animal knows well enough, being both attracted and excited by the powerful pheromones she produces. Once pregnant, females lose interest in males and will not return to oestrus until they are close to finishing suckling. Females are sexually unreceptive except during ovulation and do not copulate during the rest of their cycle or when pregnant. Even highly promiscuous near-neighbour species, such as chimpanzees, have greatly reduced receptivity outside oestrus. Many species ovulate only at certain periods of the year, timing intercourse to produce young in spring, when the abundance of summer and autumn food will provide the best possible chance of survival. If an oestral female is part of a harem, the male will recognise her state and mate with her. However, she will not be loyal to him and, if opportunity arises, may mate with any other available male. To ensure paternity, males try to monopolise fertile females and keep other males away. If one succeeds, her young get the benefit of the size, strength and alertness he demonstrates to do it; if he fails, she maximises her chance of getting pregnant and her young might benefit from the opportunism of their actual father. The sexual selection here is for size, strength, opportunism and alertness. In many non-harem species, females "on heat," or in oestrus are courted by numerous males. Depending upon the species, females mate either with the male of her choice or with the one who wins the battle for her favours.
Female primates, normally ovulate throughout the year and produce a very pronounced swelling and colouration of the genitalia as they do so. Our closest relative is the chimpanzee, among whom the vulva becomes bright pink and swollen during ovulation. Males can hardly miss seeing which females are fertile and, in case he does miss the point, females actively display their condition to males, their swollen vulva acting as a sex attractant. During ovulation, female chimps copulate repeatedly and promiscuously, but show a preference for the à-male. (See de Waal (1982).)
Humans are different. Bipedalism, erect walking, would be impossible with the female genital arrangement of other primates and female sexual organs have moved forward and no longer swell during ovulation. The mere absence of swelling would not prevent a woman advertising her fertility by pheromone production but, while human pheromones certainly exist, they are far less powerful than those of many animals and ovulation in humans is almost undetectable either by a woman or her partner. Human ovulation is said to be cryptic or hidden. At ovulation, women do experience a slight rise in body temperature and sometimes, if a woman especially wants to become pregnant, couples may monitor her body temperature, with the aim of engaging in sexual intercourse during ovulation, when pregnancy is most probable. Also, apparently, a woman's behaviour can change during oestrus and it is reported that she can become unconsciously more flirtatious or promiscuous at that time.
Female mammary glands, the breasts or milk producing organs, are an essential part of mammalian reproduction. In most mammals, breasts are undeveloped until after a birth, when they swell so that a mother can feed her young. Uniquely, in human women, breasts grow during adolescence and remain permanently developed thereafter, though often enlarging after childbirth. In humans, as well as providing milk to infants, breasts take over the roles played by the swollen vulvae of other primates and act as sex attractants and erogenous zones. By contrast to primate vulvae, female breasts are permanent attractants and women are sexually receptive during the non-fertile parts of their cycle, remain so while pregnant and even after the menopause - all times when it is impossible for them to conceive. For their part men, though showing no obvious anatomical modifications, are sexually attracted to women outside their fertile periods. In sum, human biology is evolutionarily adapted so that most acts of sexual intercourse occur when pregnancy is not a possible outcome.
9.3 The Menopause
Girls usually start their menstrual cycles with a menstrual period at age 11-13. Menstruation then occurs every month, for the next 35-40 years. Periods and the monthly ovulatory cycle cease at age 45-55, when a woman undergoes the menopause and she is, thereafter, unable to bear children.
The menopause is nearly unique to humans. Ridley (1993) mentions that the pilot whale may suffer a similar cessation of ovulation and, since whales are hard to study, the same may be true of other large cetaceans. Also, the author has heard that elephants may have a menopause but cannot cite any literature.
The biological role of menopause in humans is normally taken to be linked to the time it takes to rear children. A human mother must feed and defend her children for 10 to 15 years and, in the wild, human infants have no real chance of survival without adult support. However, her expectation of life declines with advancing years, as does her ability to stave off external threats. By age 50, the time of the menopause, her chances of successfully raising further children are slim.
The interests of her genes, it is argued, are best served by devoting her energies to her existing young or to helping to raise her grandchildren, the next generation. She is especially fitted to the latter role as she is a repository for the accumulated wisdom of her group. Grandmothers, it is argued, have a positive biological role, to encourage and enable their own children to produce grandchildren, to share the burden of raising them and pass on the skills and knowledge needed to do so. The menopause, like cryptic ovulation, is a biological adaptation to level3 knowledge.
Human pair formation is such an unusual behaviour it needs explanation and it does not occur solely in civilized man. Humans are biologically and psychologically adapted to stable, sexual relationships, usually in pairs, though sometimes to relationships in which the male has several partners. In all sexual species, male and female must be mutually attracted at certain times. There is always this basic socialisation between male and female. Following the principle that evolution modifies an existing phenomenon, rather than creating a new one, human sexual biology and sexuality have become modified so that men and women are permanently attracted within stable pairs.
Despite their permanent sexual receptivity, human females are far less promiscuous than chimpanzees and far less inclined to promiscuity than human men. In many cases, a woman's sexuality is such that she will not offer intercourse to any partner other than a regular mate, permanent partner or husband. This inclination to monogamy among women is biological, not cultural. In species where females are promiscuous, such as chimpanzees, much of the sexual selection arises from competition between sperm inside the female reproductive organs, with most offspring being fathered by males who deliver many sperm in each ejaculate. Consequently, in species with promiscuous females, there is pressure for males to produce ever more sperm and they develop large testicles with high sperm density. Testicle size and sperm density therefore indicate the natural level of female promiscuity and the size and sperm density of human testicles indicates that human females are not, naturally, highly promiscuous.
This combination of female sexual biology and monogamous sexuality creates the regular sex and permanent partnership found of most human, sexual pairs and men are as adapted to it as women. In many species, males try to ensure paternity by monopolising a female's sexual activity while she is on heat but men cannot do this. Most male animals need only stand guard while the female is ovulating and on heat, after which he can pursue amorous adventures elsewhere. Men cannot tell whether a woman is fertile. Her sex attractants, her breasts, are permanent, as is her sexual desire. For a man, monopolising a woman's sexuality, and ensuring his own paternity, is a full time job, involving permanent pair formation. In a primitive world, lacking eunuch slaves at the harem door or knowledge of menstrual cycles, the path to paternity is partnership, to which men are as adapted as women.
Another human peculiarity is female orgasm, which seems absent in the females of other primates but which women often experience during intercourse. Presumably women enjoy sex more than most animal females and, commenting upon this, Morris (1977) remarks that, "the human female is therefore more powerfully rewarded by the culminating moments of her sexual encounter and in this way becomes more strongly bonded to her male partner." Human pairing continues even after the menopause, when further offspring are out of the question and many older human couples report continuing to enjoy a sex life well into old age. Clearly, reproduction is no longer the sole purpose of sex, there is a great deal of additional intercourse going on. The primary purpose of all this extra human sexual intercourse is stable, mating pair formation and the purpose of pair formation is the rearing of children. The unique adaptations to female sexual biology and sexuality are, therefore, driven by the need to transmit level3 knowledge to the next generation. Cryptic ovulation, permanent breasts and receptivity, the menopause, female orgasm and preference for a permanent mate are all adaptations to social, level3 knowledge.
It is so normal, so seemingly natural, for men and women to raise children within a stable mating partnership, usually marriage, that we hardly think about it. Actually, this stable bond between men and women is an unusual behaviour among mammals, where mothers normally raise offspring without paternal help. The mammalian norm is understandable in terms of competition for mates and resources. The facts of biology commit female mammals to rearing the young but once a male has impregnated a female, his genes are usually best served by letting her get on with it and pursuing other partners.
Level3 knowledge and prolonged childhood change that balance and human sexual adaptations are the response. Parental partnership is necessary if children are to be supported to adulthood. Regular sexual relations are the social glue that draws men into that partnership and ensures that children enjoy physical protection, material support and teaching from both parents. Female sexual biology is adapted to ensure her partner is loyal and her sexual preferences help to ensure he can deliver his side of the bargain; women prefer men who are physically big, strong, smart, rich and socially powerful. The sexual adaptations most visible in women serve to make sex, and the private, mutual, intimate pleasure to be derived from it, into the glue that joins human adults into parental partnership.
Human sexual adaptations, being more obvious in women, are often portrayed as a deal they offer men, "if you help with the kids, I'll give you regular sex." That picture is biologically wrong and rather assumes that men and women are from separate species. The correct perception is that both genders have evolved into their sexual bargain. Pair formation is a mutual deal that creates obligation and advantage to both parties but it is an imperfect deal and both men and women can cheat, though they tend to do so in different ways.
Men are slightly bigger than women and there is a rule, among animals, that the larger is the male, compared to the female, the more mates he will keep in his harem. Hence, in nature, humans are mildly polygamous and naturally form small harems. Multiple wives are considered normal in many cultures and wives often accept the arrangement, albeit with less enthusiasm than their husbands. When a paired man cheats, he seems to be trying to form such a harem, seeking new, additional, long-term female partners. So, western men often take long-term mistresses and, if the male is of high social status, the wife often tolerates the arrangement and remains loyal despite the infidelity. The wives of philandering, lower status males often leave. Other men achieve a sort of serial polygamy as older, first wives are succeeded by younger replacements. (See Townsend (1998) for an extended discussion.)
Powerful men can also try monopolise women, for example, by achieving such a dominant social position that other males are deterred from approaching them - the gangster's moll comes to mind as a modern day example. In England, the ancient right of droit de seigneur enjoyed by the local squire over his serfs manifested much the same trait. In some societies, well- placed males can effectively imprison their partners. The royal harems of the middle east, with eunuch slaves guarding the entrances were clear examples.
Women are no more virtuous than men but seem less inclined to multiple partnerships. Unfaithful wives top up their sex lives with secret, casual, matings, cuckolding their partners rather than replacing them. There is also some evidence that, without conscious knowledge, women are most likely to seek such encounters during ovulation and such matings produce substantial numbers of children. DNA studies repeatedly show that, in the west, about ten percent of all children were not sired by their ostensible father. That figure may seem shocking but it is a low level of promiscuity compared with chimpanzees, among whom paternity would be impossible to determine without DNA tests.
Among higher primates, long term pair formation is rare, it is practised by gibbons but they live as distant, solitary pairs, with little social life and the males take no active part in raising offspring. The most common reproductive strategy in mammals is harem formation by a dominant male, who is regularly cuckolded by less dominant competitors. Mating followed by departure of the male is also common. The central reality among humans is that men and women mostly honour their family deal. They sometimes cheat but it is the cheating that harks back to animal behaviour and is easy to understand. The human willingness to make and honour a sexual and parental deal is unusual and needs explanation.
Men and women are biologically and psychologically adapted to stable sexual pairs and to cooperative parenting. Humans are a pair-bonding or mildly polygamous species, mostly adapted to heterosexual, pair-bonded relationships. Humans seem to have reinvented pair formation and our sexual adaptations are the mechanism whereby that has been achieved. They create a male- female contract that marks humans out from other animals. Despite the cheating the sexual, pair-forming deal between men and women has clear origins in human biology. It follows that conformity to that deal has been one of the more successful strategies humans can adopt. The advantages this deal offers have their origins in level3 knowledge, suggesting that one might be able to discern parallels between epistemology and sexuality.
Evolutionary theorists depict the origins of cooperation and altruism as evolutionary theorists by modelling social situations with a strategy game called The Prisoner's Dilemma Game. Details will not be given here but it is discussed in Dawkins (1989) and Wilson (1980).
In these games, two players make moves in rounds and win a prize, or pay a penalty with each move, while the size of prizes and penalties depends on the moves played. In its classic form, the game allows only two moves, cooperate or defect and each player plays either cooperate or defect without knowing the other's player's intentions. Four possible situations emerge, the two players cooperate, one defects the other cooperates (this is actually two situations, as it may be player A or player B who is cooperative) or both defect. If both players cooperate, each wins a small prize. If one cooperates and the other defects the defector wins a big prize and the cooperator pays a big penalty. If they both defect, both pay a smaller penalty. Prisoners dilemma games are not "zero sum" games and, by continuous mutual cooperation, both players can be sure of winning and, if they both continuously defect, both can be losers. Equally, a player who continuously cooperates with a defector would be a heavy loser.
The problem is, if a player is acting rationally, under what conditions should he cooperate and under what conditions compete by defecting and trying to gain more money at the expense of the other player? The answer depends upon the prize structure of the game and it is necessary to explain the idea of a "zero sum" game. Zero sum games arise when the total prize is fixed or zero, if penalties cancel out prizes. In such games, players can increase their own prize money only by reducing that of their opponent, thus leading to competition. For example, in a tennis match the total prize fund is fixed at the outset, with the winner receiving, perhaps, twice as much as the loser. At the beginning of the match, the two players could do a pre-match deal to distribute that money equally but a strong player, who expects to win, would never make that arrangement with a weak player. In zero sum games, rational play leads to competition.
In non-zero sum games, players can increase the total prize money by cooperation. If the advantage is sufficient, rational players start to cooperate with one another, their mutual cooperation improving both their prospects. This situation can occur in competitive sports. For example, during long distance cycling events, such as the Tour de France, the leader must work hard against air resistance while the second rider, slipstreaming him, works less hard to keep up. When two cyclists break away from the main group of riders, they begin cycling cooperatively, like team members, and alternate the lead. Working together this way increases their average speed and helps them to stay ahead of the main pack. Hence, their total prize is increased, at the expense of the pack, who are not part of this sub-game.
Non-zero sum games are common in living systems and often lead to cooperation. They are the fundamental reason hunting animals often form groups. A group hunting together, gains many more kills than the same number of predators hunting separately. Likewise, in many bird species, the male and female cooperate in raising young. Here the game is really played by the male, will the increased success arising from cooperating in bringing up this brood outweigh the loss from not trying to impregnate another female? In birds, the answer is often yes and the avian parents cooperate in raising their brood. In mammals, the answer is rarely yes but humans are an exception.
Although many mammalian mothers teach hunting or feeding techniques to their offspring, the amount of information transferred is tiny. For most young animals, the important thing is to grow very fast, to minimise the period of small size and vulnerability to predators. Humans are different because raising children is more than just feeding them, they need to learn a great deal of level3 knowledge.
A child is safe enough in the social womb of their tribe but they are incomplete until they possess a full set of social knowledge. Rapid growth is not the best option for human children. They need to grow slowly because, after adolescence, adults will perceive them as competition and close doors to them. Children who grow too quickly will not learn the group's ways and will be disadvantaged during adult struggles for status and mates, they will become unfit adults due to their lack of level3 knowledge.
For the same reason, many adults commit great effort to teaching their children and genetic explanations of dual parenting take this situation as a starting point. One parent could not undertake the parental burdens of feeding, protecting and teaching alone or, at least, could not do them so well as both parents together. A single mother must commit so much time and energy to finding food and protecting her children, she will have none left for teaching them. Even if she succeeds in raising them, they will be disadvantaged by a lack of knowledge, since she has spent so long feeding them, or by poor nutrition in childhood.
This is why human parents form pairs. Two parents can give their children both the protection and learning needed for the best possible start in life. Parental partnership keeps children safer during their prolonged childhood, it gives parents more time to teach them and it gives them two parents from whom to learn instead of just one. All this means that children are more likely to learn the knowledge they need to fit into social groups if they have parents who remain together. It seems a good argument.
Geneticists thus explain cooperative parenting in humans as arising from a non-zero sum game. Two parents, working together have a good chance of nurturing their children through a long childhood and teaching them how to be fit members of a social group. Either parent, alone, would have less than half that chance. For primitive humans, parenting is a non-zero sum game and rational parents cooperate.
The evolutionary explanation for cooperative parenting seems valid but, like all genetic arguments about human behaviour, it says nothing about the immediate feelings and motivations of the people involved. Genetic adaptation leads to cooperation by being expressed in the psychological, emotional and biological makeup of individuals. Parents do not experience some distant, future genetic advantage. They pair and nurture children in partnership because both experience individual advantage in doing so.
People do not experience genetic games, rather they experience another game based on personal feelings. They ask themselves, do they feel more, or less, satisfied within the pair than outside of it and both derive a large emotional and physical pay off from cooperation that cannot be achieved by defection. It tips the balance of their emotional prisoner's dilemma game in favour of cooperation. Human sexual biology and sexuality are adapted to create desires that can be satisfied only by mutual cooperation and the cooperation that begins in the bedroom finds expression in other aspects of their lives. Sexuality is adapted to make two parents cooperate and become one, stable team, thus creating the environment needed for rearing and nurturing children. Perhaps the man would be genetically better off were he free to sow wild oats; perhaps the woman could find a stronger or wealthier supporter but, for both, the pursuit of such uncertainties would jeopardise the real rewards of a current relationship.
Adult sexual biology and sexuality provide the mechanisms that keep parents together in partnership to raise their children but a family team has power relationships and is a small hierarchy. One can as validly say that their sexual traits are a route through which men and women exercise power over one another. Sexuality gives both partners the power to influence the other's actions and either the man or woman can become dominant, the team leader, the other exerting power through subordination. Traditionally, the dominant role falls to the man, hence the phrase, "to wear the trousers," but that phrase is often applied in reverse, to reflect the dominant role the woman plays in a particular relationship.
A further insight into the origins of dual parenting comes from taking a bioepistemic perspective and focusing on knowledge in general rather than genes. Human evolution involves the inheritance of pools of both level1 and level3 knowledge. A father can propagate level1 knowledge by impregnating a woman, then moving on to the next female, but that does nothing for his level3 knowledge and he is at risk of leaving behind children who are unfit due to ignorance or through the weakness of the groups into which they were born. If a father is to pass on his social knowledge, he must do more than plant a child in its biological womb, he must also ensure the strength of its social womb. A father who remains with his children does this and adds his social knowledge to the genetic knowledge they have already received from him.
The father protects and feeds the family but his nurturing role goes beyond merely supporting the mother. Some forms of knowledge are gender specific and unavailable to women. Men are bigger, stronger, faster, more aggressive and have better spatial coordination than women. They seem adapted to be hunters and warriors, defending and partly feeding the tribe and there is a great deal of knowledge associated with those roles that only the father can teach children. His presence extends the range of social knowledge children will learn and creates a route down which male-specific knowledge can pass. This type of knowledge would not evolve and grow unless fathers were naturally involved in child care.
In summary, human groups must involve men in child rearing if they are to evolve a fully useful set of level3 knowledge. Without that involvement, the group would fail to transmit and develop the social knowledge inherent in gender-specific male roles and would be defeated in competition with other groups who were not subject to such a failing.
The human brain and our other knowledge processing organs, the voicebox and hand evolved through sexual selection mechanisms similar to those that generated the peacock's tail. The same applies to other unique human traits and the present human form arises from a pattern of such arrows with associated human sexualities. Such arguments normally use the sexuality of one gender to explain the phenotype of the other. For example, the peahen's sexuality explains the peacock's tail but it is equally valid to argue the other way round and explain a sexuality from a phenotype, so that one can examine human sexuality in terms of phenotype.
Humans differ from peacocks in forming long-lived mating pairs, with both genders making a selection. In peacocks, only females choose, so that only the male phenotype is modified. In humans, both men and women make choices whose pattern modifies the phenotype of the other gender. The sexualities now detectable in humans will be part of evolutionary arrows that enhanced the development of level3 knowledge and thus directed our evolution into the vacant evolutionary niche of culture. The differences in sexuality exhibited by men and women arise from the different roles men and women play in the social group of the family. Of course, the ultimate role of that group is the transfer of level3 knowledge from one generation to the next.
It is also useful to reorient thinking about our knowledge handling organs, the brain, hand or voicebox. This reorientation helps because our brains are of no value without people to learn from, speech is useless without someone to talk to and hands are limited without demonstrations of how to use them. Brains, voicebox and, in part, hands are organs of social knowledge, part of the mechanisms creating social groups, including the sexual pair, the family and the knowledge that underpins them. People should display sexual preference for brains, voicebox and hands, because of their social role, but in a sense they are only intermediate targets for the arrows that produce them. One may think of these arrows as ultimately aimed at a more distant, more fundamental target, namely the knowledge that holds the family together. This knowledge is not a phenotype, it is, in Dawkins' (1982) phrase, an extended phenotype but there seems no reason why it should not be the target for an evolutionary arrow, even though it occurs, not in the other gender, but in the social "we" of which both genders form a part.
Before any specific sexuality becomes relevant, there is a very basic aspect of sexuality that needs to be explained, namely the fact that the fact that men and women are different heterogeneous and different people find different stimuli sexually attractive. So, men are attracted to different things from women and sexual preference varies from man to man and woman to woman.
The ultimate source of heterogeneity is group selection and the fact that successful groups are composed of people inclined to fill different social roles. The ultimate source of the different male and female preferences is the different roles men and women play in the small social group that is the family, women in child rearing and home making, men as provider and defender.
Men are most attracted to young women (Townsend (1998)), because they are likely to be able to bear and raise children. Health is another requirement of child-rearing and men are attracted to clear skin as a signifier of health, (another possible origin of human loss of fur). Women should also have wide hips, for easy childbirth and large breasts, to indicate breast feeding ability. Male fondness for the breast will have created the arrow that made it permanent. (Newborns of all mammalian species are attracted to their mother's mammary glands and the sexual attraction adult men display for it seems another example of neoteny, see section 8.6.). Also, as Marilyn Monroe showed, men like women who are mildly plump, so displaying the reserves of nutrition needed for pregnancy. The whole pattern indicates that the primary role of women is child rearing and men are attracted to corresponding aspects of the female phenotype
In the family, women also cook and keep the house clean and men are attracted to women who cook well and keep a clean house.
Women are attracted to men who are tall, athletic, aggressive, politically powerful or rich, traits linked to the ability of such men to defend the family against external threats. They often prefer men who are older, provided they possess the resources and power needed to support and protect potential offspring. Women like men who are confident with a lot of talk, who are willing to make and break rules and possessed of a sense of humour. This is consistent with the idea that the main family roles for men are defence against enemies, hunting and discipline. The husband and father makes the decisions and carry them out, he makes the rules and enforces them. Like the mother, he also takes part in child care, though his role is quite different from hers; he is more likely to be involved with older children and be more authoritarian.
Women often like men to display their inclination to social dominance in their sexual relationship. He should the suitor, the initiator, the pursuer, the hunter, the conqueror; she should be the pursued, the prey, who hopes to be defeated and so seize power through subordinacy, to yield her body to a man who will be lover, provider, protector, guide, mentor and also instrument. Both men and women seek the partner who can offer their ideal family relationship.
Both genders are attracted to those they believe will be faithful and monogamous. The coyness and shyness common in both women and men, can be attractive as an indicator of potential faithfulness. Both genders are attracted to potential partners who are fond of children and likely to be committed to their own.
Bioepistemic evolution can enrich these explanations by adding that the subordinating female seeks a male to act as a source of level3 knowledge, to supplement the genetic knowledge already offered as sperm. He must both possess level3 knowledge and show the dominant political behaviour required to pass it on to her and, though her, to their children. The man seeks a younger, subordinating female to be a willing learner and thus become a channel through which his knowledge will reach his children.
If the differences between male and female sexualities can be summarised, it lies in the targets of their sexuality. Males focus on the female biological phenotype and the role she might play in his life. Female sexual targets are less about male biology than about the social group she perceives her union with him might create and she is attracted to the social roles a man plays or seems able to play. A man focuses on his partner and her physical attributes, a woman on the "we," she might create with this man.
All human groups form hierarchies and the permanent mating pair and family are not exceptions. The sexual and social processes that bring a man and woman together have evolved because they create modalities of mutual power and control upon which the stable existence of the family depends. A woman's "offer" to raise the children is driven by biology and supported by an offer of sexual availability, home making services and social support within the larger group. A man offers breadwinning support, protection and help with the children as well as sexual services.
This is sometimes described as a "deal" and does resemble an exchange of compensatory power, an act of trade, in which each partner controls the other through transfers of money, political support, sex and home making services. Other forms of power are expressed within the same family grouping. For example, men often use their greater strength and athletic ability to assert condign power with violence and, in the wild, this is undoubtedly a factor that makes males dominant. Women often exert condign power using their social expertise, by spreading malicious gossip among the community at large, a modern manifestation being the kiss and tell stories in the Sunday papers. Both parties often try to control the pairing by withdrawing the mutual services that formed the pairing.
In successful partnerships, ultimately the most important form of power is conditioned power. The mating partners who form the nucleus of a family group engage in extensive mutual communication, a process that increases their shared level3 knowledge set and provides them with common interests, vested interests and ideology. Hence the two partners merge into the we of their partnership, a process that will be easier if they have similar backgrounds and compatible, personal aims. Whatever their backgrounds, their aims will change and merge over time, as each alters the level3 knowledge set of the other and each comes to seek power through subordination to the communal "we".
Children, when they arrive, are subordinate to both their parents, learning their language and customs and taking on an identity approximating that of the "we," the family. Parents protect, teach and support their children, altruistic acts underpinned by kin selection and self-interest since, by suitably selecting what they teach, parents can hope their children will become allies during any future conflict.
There is a very basic property of human beings that needs to be explained, namely the fact that we are sexually heterogeneous. Although the majority of men and women display a pattern based on that described in section 9.10, there is great scope for variability within that pattern. Hence, some women are attracted to athletic men, others to older men; some men are attracted by a woman's figure, others to the way she might dress. Such differences produce great heterogeneity, even within the pattern regarded as normal, and it just is a fact that different people find different stimuli sexually attractive.
The differences between the sexualities of men and women were accounted for by group selection and the different roles they play in the family, a small social group. Variability within a gender also needs accounting for and, again, the ultimate source of the heterogeneity is group selection but this time the groups concerned are larger groups, such as tribes. That is, ignoring simple randomness, each gender exhibits sexualities that reflect the variety of roles the opposite gender must play if their larger social group is to succeed in competition with other groups.
Those different roles were outlined in chapter 7 and are produced by the ways data and knowledge are generated, distributed and used in a society. Some hinge around elite activities, some around middle hierarchy or subordinate roles and some around the various divisions of labour necessary to construct a society. Those different roles are not performed by all people, neither are all people capable of performing them or inclined to do so. Because there are a variety of social roles, successful human groups need to contain a mixture of human phenotypes even within a single gender. For example, there will be an optimum ratio of men inclined to lead and other men inclined to be followers; a surplus of either will tend to favour the other trait, so that neither will be eliminated. Each phenotype in this heterogeneous population will be produced by sexual selection, implying an equally heterogeneous population of sexualities in the other gender to produce the necessary evolutionary arrows.
The net result is that, in normal human populations, each gender will display a mixture of sexual dispositions. Those in men reflecting the social roles of women and vice versa.
Most animals mate purely to procreate. Their sexuality is adapted to transmit level1 knowledge and their biology and behaviours clearly show that aim. If reproduction is impossible, animals prefer eating to mating.
Humans are different and, though we procreate through sexual intercourse, children are not the immediate purpose of most of our sexual acts. Human sexuality has changed and adapted to draw men and women into the long term social groupings needed to transmit level3 knowledge to children. Men and women are interested in sex at all times, outside oestrus, during pregnancy and after the menopause. This expression of sexuality produces a pair bond between men and women, creating an environment in which children can learn and be taught by both parents; it adds the menopause, so that grandmothers too become active agents in raising and teaching children.
Human children are adapted to live in a family environment and be subordinate to the adults who exercise power over them. Conditioned power is exercised by transferring knowledge in two ways. Firstly, by educating young offspring by demonstration and teaching, a role initially discharged mostly by the mother but the father also contributes. Secondly, parents control their children who, being subordinate, look to them for that control and learn from the patterns and modes through which it is exercised. The educational and political choices parents make condition their children and give them the language and other level3 knowledge of their group. Children are adapted to learn in the family and, once they reach adulthood, create the same environment for the next generation.
The unique traits that make it possible for humans to create man - woman social pairs are their sexual traits, a fact that can lead to confusion when thinking about the evolutionary arrows that lead to them. These changes in sexual biology will be linked to changes in sexuality but note that it is change in the sexuality of one gender that drives change in the sexual biology of the other.
If animals were the norm, most human sexual activity would be deviant but these human deviances are normal for our species. They are written into our biology in the form of permanent breasts, cryptic ovulation and the menopause and arise from genes not upbringing. It is impossible to determine from the bones left in the fossil record when these changes in our sexuality might have taken place but they probably appeared alongside our ability to handle level3 knowledge. Laying reproduction aside, human sexuality generates the socialising urges that create society and the ambitions, motivations and struggles for hierarchy that give it a dynamic.
The social achievement of all these sexual modifications is pair bonding, the union between one man and one woman that creates a stable social environment, the family group, in which children can be nurtured. One can look at this situation another way and note that the social relationship, the man - woman social pair that is the mainstay of human families, is a modified form of the sexual relationship that already existed in our animal ancestors. This is not surprising, since evolution modifies what exists, rather than creates de novo. Aeons ago, when our mammalian ancestors were just forming family relationships, one force, sex, was already driving male and female together. It became modified to bring them together in long term pairs. The biological drive of animal sexuality is modified in humans to create stable social pairs and the evolutionary forces that drove their creation originate in the need to transfer knowledge down the generations.
The argument given in the last paragraph will soon be generalised and extended; it will be postulated that all adult social pairings are modified forms of the basic social-sexual relationship seen between man and woman; that all social pairings are modified forms of sexuality and that the social relations that formed the man woman pair, subsequently became modified to produce all other social pairings. It will be argued, for example, that the male - male and female - female social pairs are modified forms of sexual relation and that the evolutionary forces creating them originate in knowledge. Those relations too would be adapted to create the social and authority behaviours needed to transmit level3 knowledge around social groups and down the generations. Before developing that argument, or elaborating the discussion of any specific sexuality, it will be useful to compare sexual intercourse with social communication.
There are many analogies between sexual intercourse and verbal communication, sometimes called social intercourse. In sexual intercourse, the sperm transferred contain level1 knowledge, which may take control of the recipient and make her pregnant. Sexual intercourse involves transfer of level1 knowledge, a transmitter, a receiver and the possibility that the transmitted knowledge will take control of the receiver. In verbal communication, the data transferred contains level3 which, may take control of the receiver and change his or her beliefs. Social intercourse involves transfer of level3 knowledge, a transmitter, a receiver and the possibility that the transmitted knowledge may take control of the receiver and change their behaviour. In both cases the transmitter is dominant the receiver subordinate.
Expanding that analogy produces an unusual cross-disciplinary study. Traditionally, epistemology has been part of philosophy, albeit one to which evolutionary theory is often applied. So, while sexuality and evolution are part of biology, there is no conventional scientific home for the study of knowledge. The current scientific view of it is best represented by the field of cognitive science, a blend of information technology, neurobiology, psychology, linguistics, political science and philosophy. Gardner (1985) and Stillings et al. (1987) are good reviews. However, the directions in which cognitive science has developed conflict somewhat with the present work and it is doubtful how far one should follow its example. In this author's opinion, it has weaknesses. Two of its hard sciences, information technology and neurobiology, actually sit rather uneasily in the mix and have not developed to a point where they merge with rest of the field. Also, it is social, level3 knowledge, that distinguishes human beings from other animals and social sciences are represented only by political science, which is not central to that area. One feels that cognitive science should pay more attention to sociology.
However, political science does recognise that communication as an assertion of power. The transmitter takes a dominant role, analogous to the male, the receiver a subordinate role like that of the female. During social communication, biological genders are irrelevant but social hierarchy defines a communicative "gender," the communicative "male" being the person placed higher up the hierarchy, the communicative "female" being placed lower in it. Hence, in this context, social hierarchy is analogous to gender, with most individuals capable of being communicatively male or female, depending upon the other party to the communication.
Interestingly, biology offers sexual analogues to this sort of hierarchy. Many species of bacteria, protozoa and moulds mate through conjugation tubes and such species can have multiple genders. Male bacteria have a "pilus" on their outer surface, the genes for which are coded on an episome, a circle of DNA separate from the main chromosome. To initiate conjugation, the bacterial equivalent of mating, the pilus adheres to the surface of a female cell and becomes converted into a conjugation tube, down which a copy of the episome is transferred. If a bacterium has no pilus, it can only take the female role but otherwise there seems to be a hierarchy of episomes, with "gender" in a particular mating depending upon position in the hierarchy. At least one species of slime mould, which mates by fusion of cells, has a similar sexual hierarchy with thirteen different genders. In any particular pairing, the male, who transmits information, is the individual placed higher on the hierarchy, the female, who receives the information is placed lower (Ridley (1993) p98). Sexual relations can thus be read as analogous to many aspects of social communication and that analogy suggests that one can look for sexualities corresponding to different communicative pairings in human groups.
All social groups can be divided into pairings, for example, man - man; man - woman etc. and these pairings must form before knowledge can be transferred across that particular social interface. As mentioned in section 9.13, and rather supported by the last section, social pairings may actually be modified forms of sexual relationship and we will take the view that they are indeed just that. So, for example, where there is knowledge transfer from man to man or woman to woman, the human capacity for the social relationship that leads to the transfer, evolved by modifying sexuality to meet the requirements of that pairing. This conclusion is important and will be needed for the next chapter. This section will develop it by reviewing the strength of some possible social pairs.
A society is an interlacing web of communication, each act of which involves a social pair with a transmitter and a receiver. We can classify social pairs according to the people playing those two roles. The result is a two dimensional classification, one dimension identifying transmitter and receiver and the other dimension identifying the people involved. There are communications between men and women, between adults of the same gender (this is two situations, depending on gender), between adult and child (again two situations) or between children. These two dimensions are enough to generate twelve communicative social pairs. A dimension for hierarchy would be useful but will be omitted from the table; when it is needed it will be indicated in the name of the pair by a phrase such as "down to." More pairs could be obtained by incorporating mature people or adolescents but that too will be omitted.
A third dimension based on type of social organisation will be included. As mammals, we will have evolved from a situation where our young were raised by mothers without fathers, through a time when they were raised by pair-bonded family groups and/or polygamous groups and finally to larger social groups, such as tribes, composed of several family groups. This gives us four types of social organisation.
Mammal with purely maternal care (m).
Mammal with stable family group (f).
Mammal with stable but polygamous family group (p).
Tribal group (t).
As one goes down this series, new social pairs develop in each of them. For example, the first three involve no male-male social interactions while the tribal group does. These different groupings could only develop if the genetic capacity for the social pairs they contain is available to the individuals who compose them. The following, table gives some examples of social pairs and the groups they might be present in - each cell in the table can have four entries, one for each social grouping, indicated by the lower case letter, m, f, p or t, to be interpreted as in the above list. The scale goes from 0 for no interaction, through 1, for a weak pair, to 5, for a very strong social pair. The scale is quite arbitrary and subjective, being intended purely to give a indication of the likely relative strengths of each pair. For example, 5 on the top line for "female and juvenile" indicates that young who are cared for solely by their mother, are given very close attention by her and the 4 in the next column indicates that they pay almost as close attention to her; the 3 in the last row indicates that males living within tribal groups will interact and communicate with other males much more than those living in groups with only one male.
A and B
A to B
B to A
Male and Female
Female and Juvenile
Male and Juvenile
Female and Female
0 m, f
0 m, f
Male and Male
The progress from one social situation to another, has been achieved by adding capacity for different social pairings. Each social pair arises as a modified form of sexuality and is developed by sexual selection. One gender's sexual preference drives the sexual selection, and the other gender's sexuality is modified to achieve the interaction. For example, a man who is successful in his interactions with other men will be politically successful and therefore attractive to women. Female sexuality will, therefore, produce an arrow encouraging male - male interaction, which is a modification of male sexuality, without the "purpose" of making that interaction overtly sexual. This point will be pursued in the next chapter, when the origins of homosexuality are discussed.
9.16 Mother and Baby
There is one social pair besides sexual relations present in all mammals, namely that between a mother and her young. It is as old as mammals and it could be argued that it does not arise by modification of some earlier social pair. In fact, at least in humans, it seems to have become the most overtly sexualised of all non-sexual relationships. Inadequate nutrition during the early stages of a child's growth can permanently impair brain function and breast feeding is, therefore, extremely important. Mammalian mothers, of all species, must find breast feeding a rewarding experience if their young are to grow properly. This is, presumably, why a woman's breasts have become erogenous zones. (The author has no information on the sexual responsiveness of mammary glands in other species but presumes that the mother gets some reward for allowing her young to suckle.) In any event, evolution has introduced a sexual element into the human breast feeding relationship and it seems very likely that its function is as described above.
Humans develop the mother child relationship into a protective, caring environment and within which the young can learn. In short, mothers love their children and the sexuality of their relationship can also be seen in the similarities of address and language with which men and women engage with babies and with sexual partners, who are very often addressed and treated in an infantalised way. The word, "baby," in a love song, rarely refers to an infant, while the word "love" is used to describe the feelings inherent in both relationships.
The mother baby relationship is the sexualisation of a non- reproductive affiliation. The feelings inherent in sexuality began as a social glue to create the male - female relationships needed for reproduction. They became adapted to act as the social glue for another important relationship, that between mother and baby. In forming this glue, sexuality is adapted in such a way as not to lead to actual intercourse.
Sexual and maternal relationships are enough for some mammalian life cycles but human society involves many more social pairs than those of man - woman and mother - child. These extra social pairs, it is argued, are also maintained by social glues adapted from sexuality, again modified to stop short of intercourse. The next chapter, which discusses the subject of sexual "deviation," might be seen as an exploration of that possibility.
© This page is the heterosexuality page from the site sexandphilosophy.co.uk, all of which is copyright to the author, Dr. John A. Hewitt.
This page is taken from and modified from one chapter of an early draft of "The Architecture of Thought" by John A. Hewitt. It is copyright but not definitive and differs in detail from the final version. If you wish to cite it, please check a copy of the published book.