XXVIII The Science of Sex

Dr Robin Baker’s Science of Sex: A Discussion

The Science of Sex is the subtitle of one edition of Dr Robin Baker’s work Sperm Wars (1996), a book that was followed by the equally important Baby Wars (1998) and Sex in the Future (1999). This Sex Wars trilogy provides the broad public with tremendous insights on human sexuality and human nature, based on biology research. As works of scientific vulgarization, these best-selling books present the results of decade-long research and publications in scientific journals. With the present essay, my aim is to discuss a few of these major findings, under thematic heads. For an introduction, see my Reflexions XXVII (here).

References: Sperm Wars (Basic Books, 2006) (further on abbreviated as SW), Baby Wars (Ecco Harper Collins, 2000) (BW), Sex in the Future (Arcade Publishing, 2000) (SF), and Sperm Competition in Humans. Classic and Contemporary Readings, by Todd K. Shackelford and Nicholas Pound (ed.) (Springer, 2006) (SCH). The latter book gathers several papers by Dr Baker and his colleague Mark Bellis, as well as papers from other scholars, some disagreeing with Baker and Bellis, and parts of a 1984 book by the pioneer researcher in the field of human sperm competition, Robert L. Smith (University of Arizona).

Penis Shape and Size

According to Dr Baker, the shape of the human penis has been evolved in the context of sexual promiscuity and sperm competition among our primate ancestors. Not only does it allow insemination, but it also serves as a tool to remove, via intercourse thrusting, semen present in the female’s genital tract. This hypothesis has been tested with dildos and artificial matrices, and has been found to be correct. By removing the sperm already present in the tract, the male prevents it from achieving fertilization, while placing his own semen in the tract to the same fertilization purpose, in a process of reproductive competition. In species characterized by male dominance (alpha males), sexual competition takes the form of male aggressivity and aggressivity displays, on which outcome depends access to females. In species characterized by promiscuity, such as chimpanzees, access to females is open to every male, and sexual competition takes the form of sperm competition. Testis and penis endowments are similar across chimpanzees, and other promiscuous primate species, and humans (the data at my disposal concerns testis and penis size, but I suppose the same must hold true for penis shape as well, otherwise the difference would require some explanation). Sperm competition means that semen from different males compete in the female’s tract to fertilize an egg. To that effect, semen does not only contain ‘egg-getter’ sperm, whose task is to fertilize the egg, but also ‘killer sperm’, designed to destroy the competing sperm. In order to increase the performance of one’s own sperm, a male would also remove sperm from the tract during thrusting, chances being that sperm is present indeed, and that it is another male’s. The coronal ridge of the glans is here called to task, and the bigger the penis the more effective the removal.

This is the usual scenario in a context of rampant promiscuity. If we assume, now, that promiscuity is not as rampant among contemporary humans as it was among their primeval ancestors, what the man is doing while having intercourse with his regular partner is removing his own sperm from her tract, most of the time. Even if promiscuity is still widespread, in a monogamous context it is rarer that a woman cheats her regular partner with a regular lover than that she cheats him with one-off lovers, so most of the time it is his own sperm, again, that her regular partner, during their routine sex, removes from her tract. In such a context, if realistic, I suggest that the function of the penis shape as sperm remover might become an hindrance to the male’s reproductive success, rather than an advantage, because, intuitively, it seems that such a constant inseminating and removing of one’s own semen cannot be as efficient as letting the semen once inseminated doing its job. In any case, if penis shape was evolved in a context of rampant promiscuity, it is reasonable to assume that it cannot be as efficient if the context has changed.

It would be another case of some evolved trait turned dysfunctional in modern societies, such as the preference for fatty food. Such preference was evolved in times when fatty food was scarce (cf Konrad Lorenz); now that it is abundantly available in Western societies, eagerness for it has provoked an obesity epidemic of tremendous proportion in these countries. If obesity decreases one’s reproductive stamina, then obese people, because of their very obesity, will reproduce less than other people, and in this way strong eagerness for fatty food, and/or less capacity to repress it, can be expected to diminish in the population with time. This is not the case with testis and penis endowment.

As explained above, in a context of reduced promiscuity, and of monogamy, human penis shape and size may lower a man’s reproductive stamina. Dr Baker has described something along these lines with the notion of ‘sperm wars specialist’: ‘Put the specialist in a monogamous situation and he was sub-fertile. After each insemination, huge numbers of his killers and egg-getters clustered around his partner’s egg. Multiple sperm entered the egg simultaneously and dense concentration of deadly chemicals were released by the surrounding sperm hordes. The egg always died. But send his sperm in to battle, and he was virtually invincible.’ (SW 160). The ‘sperm wars specialist’ here described is the man with big testes, able to ejaculate abundant sperm, but the notion applies to men with big and well-shaped penises as well, able to dispose of greater quantities of competitors’ semen: in a monogamous situation the latter too are sub-fertile. Whatever the nature of his sperm wars speciality (testes or penis, but I believe the two are correlated), for the individual in question monogamy is fatal.

One solution to his problem is to partner with a promiscuous woman, in whose genital tract he will find plenty of alien semen to destroy, rather than destroying the egg. In such a case, a man would have to be grateful to his wife for cheating him… However, it is more likely that promiscuous women mate with promiscuous men, so his chances, competing with other sperm wars specialists, are even. As a consequence, the best reproductive strategy for such a man remains to cuckold average guys. In this way, the genes for big penis size and specific shape do not diminish in the population, although they have become dysfunctional in a monogamous context.

Female Orgasm

Dr Baker describes female orgasm as a strategy utilized by women in order to favor one man’s sperm in her tract over other men’s. It would function as a pump sucking up the semen deeper inside the tract, closer to the fertilization area. The question is whether the mechanism really is refined enough to be able to discriminate among different sperm. I lack the anatomical and physiological knowledge to answer, but such a system strikes me as most efficient and fine-tuning, given that it is supposed to have evolved, like penis shape, in a context of rampant promiscuity where females carry the semen of different males inside their wombs most of estrus time. Is the climaxing woman’s tract able to pump up semen from the ejaculating man without pumping at the same time the semen already present here after being inseminated by other men, i.e. without bringing the whole semen present in her tract closer to the fertilization area? Certainly this must be the case, and Dr Baker can make it perfectly clear with a few more words.

Beside this anatomical question, female orgasm, it must be noted, seems to be one of the most mysterious phenomena in human sexuality. The figures relative to the proportion of women experiencing it during intercourse very much differ across studies: from 30% (Hite, 1970s) to 70% (Saad, 2011), through 50% (Reik, 1940s). Somewhere between 0 and 100%, one would say, trying to make something out of it. As all these different figures have been compounded from questionnaires, this should warn us to be cautious with questionnaire results.

Then, there is the question of vaginal vs clitoral orgasm, of vaginal vs clitoral women, of the G-spot, and so on, all very mysterious, and probably myths. Also associated to female orgasm is the question of female ejaculation, which, for some scholars, does not exist, although some pornographic material is advertised as depicting female ejaculation (so-called ‘fountain women’). I am not aware that Dr Baker has discussed the latter phenomenon.

Oral Sex

In the paradigm of evolutionary biology reproduction is central, so one wonders what can be, in a reproductive strategy, the purpose of such practices as oral sex which cannot bring about fertilization. According to Dr Baker, fellatio serves two aims for the woman: via sensory clues (smell, etc), it provides her with information 1/ regarding the man’s health; 2/ regarding his faithfulness: she can detect if the penis has penetrated another vagina. Cunnilingus serves the same both aims for the man.

In this context, it is surprising that men have not evolved a dislike for fellatio, nor women a dislike for cunnilingus, since both practices expose them to negative consequences in terms of reproductive success. Knowing that a woman, via fellatio, may find him unsuitable for sex due to the state of his health, or unsuitable as a long-term partner because of his cheating, a man should search to avoid fellatio, if only to keep the possibility to cheat on the woman if it ever occurs to him that it would be to his advantage. Similarly, the woman should wish to avoid cunnilingus being performed on her.

When absence of dislike already comes as a surprise, then the fact that fellatio is mostly men’s demand, and cunnilingus women’s demand, clearly runs contrary to Dr Baker’s view. These findings are found in Eysenck, Sex and Personality (1976): based on questionnaires, ‘Women have done almost four times as many [sexual] things they disliked as men. … Only just over 50 per cent of females who had indulged in fellatio actually enjoyed doing so.’ See also Eysenck & Nias, Sex, Violence, and the Media (1979), referring to the same study: ‘Men nearly always enjoyed what it was that they had done; women in nearly half the cases said that they had not enjoyed various activities, including fellatio and ‘69’, although they had participated in them. Thus if showing oral sex in films has the effect of making this type of activity more popular among males (who after all constitute the majority of viewers of pornographic material) it would also have the effect of forcing many women to take part in fellatio, say, in order to please their men, while in reality disliking it.’ It does not make sense that males evolved a taste for a practice, fellatio, that is so contrary to their reproductive goals, and women a dislike for so useful a tool. Either Eysenck et al.’s finding is wrong (because of unreliable questionnaires), or it must be Dr Baker’s view.

Clear Eyes

People’s taste for other persons as sexual mates is based on fairly objective traits, and, unfortunately for some, beauty is not so much in the eyes of the beholder than part and parcel of the genetic endowment. What constitutes beauty is now better known by biologists; it is an aggregate of various traits that supplies the prospective mate with proof both of health and sound genetic endowment.

Dr Baker describes male beauty as follows: ‘The features she [a woman] finds most attractive are clear eyes, healthy skin and hair, firm buttocks, a waist that is about the same in circumference as his hips, shapely legs, broad shoulders, quick wit and intelligence. She is also attracted by symmetry in his physical features.’ (SW 145). He describes female beauty in that way : ‘In addition to shape, men all over the world also respond strongly to clear eyes, healthy hair and skin, and the shape of the face, particularly its symmetry.’ (SW 148). In another place, he writes: ‘In addition to shape, men all over the world also respond strongly to clear eyes, healthy hair and skin, and the symmetry of the face and body – again, features that are strong indicators of health and hence fertility.’ (BW 131).

Why clear eyes are indicators of health is beyond my understanding, and Dr Baker offers no explanation. Clear eyes are depigmented eyes, the clearer the more depigmented, with blue as the most depigmented, then grey, then all shades of green and brown to the most pigmented black eyes. Why the lack of iris pigment should be a sign of health I have no idea, and the assertion is puzzling, since in the world population at large pigmented iris is the rule rather than the exception. In fact, clear eyes are rare, they are virtually inexistent outside the white, so-called Caucasian race, which includes Arabs and Indians of India, among whom clear eyes are rare too.

The fact is even more puzzling when another trait ascribed to women’s preferences is dark skin: ‘at high cycle fertility … women … prefer relatively high degrees of male skin coloration (melanin- and hemoglobin-based) that may correspond to elevated testosterone’ (Randy Thornhill, SCH viii). Mention of high cycle fertility refers to the two dimensions of women’s sexual choice, one being the search for a long-term partner, based on social status evaluation, and the other, the search for genetic endowment. Women’s physical preferences are relevant for the second dimension, which is here under consideration. On the one hand, Dr Baker contends that women in search of genetic endowment prefer clear eyes, and on the other hand SCH affirms they prefer dark skin. A clear eyes-dark skin combination is even rarer than clear eyes alone, because in general clear eyes are correlated with fair skin. Moreover, if dark skin is an indicator of testosterone level, is it also the case with clear eyes, or rather are not dark eyes a sign of elevated testosterone?

Male Masturbation

In the context of sperm competition, male masturbation would be useful as it disposes of decaying sperm, allowing the man to inseminate more efficient semen during intercourse. Obviously, inseminating old or decaying sperm into the woman’s tract is taking the risk to have one’s semen underperform against competing sperm. Thus, while the common discourse on male masturbation is that the practice ends with the advent of ‘normal’ sexual activity, i.e. with sexual intercourse becoming regular, for Dr Baker it remains a normal activity during the whole life, when circumstances require it, that is whenever the time span between two copulations exceeds a few days. Surveys would show practice to be consistent with this, with very few men masturbating when copulations are close enough, and masturbatory activity increasing together with time span between copulations.

Dr Baker explains the popular prejudice existing against masturbation in spite of the current medical discourse (as opposed to the medical discourse of the past) that masturbation is sound and healthy, as a form of mischievous hypocrisy, by which some men would try to dissuade others to masturbate, while masturbating themselves whenever required, in order to get an edge on reproductive competition.

Since I have noted elsewhere (here, in French) the existence of such a popular prejudice, and attempted to explain it as sound, I feel bound to further explain my point of view here. My advocacy of temporarily restraining masturbation is aimed at young people having no sexual activity yet on a regular basis. I contend that masturbation places them on a physiological plane of permanent satiation, and inappetancy, no matter how frustrated these young men may feel psychologically, whereas the tension created by unreleased libido provides surrounding females with the necessary clues that the male is ‘on’ for sex; thus, a little repression would lead to quick regular intercourse, whereas by masturbation intercourse may be delayed indefinitely, as happens, I am told, with many students. I must admit, though, that in the final analysis such repression, if maintained, might lead to greater sexual indifference (and, in extreme cases of abstinence, to impotence), and thus impair reproductive success; it’s a double-edged weapon.

This being said, Dr Baker himself provides me with a situation where masturbation restraint may be advisable: the ‘sperm wars specialist’ (see ‘Penis Shape and Size’ above). As the specialist’s sperm is, in a monogamous situation, usually too powerful an engine of destruction so that deprived of sperm competition it attacks the egg itself, advising that man to inseminate not the best of his sperm, but some old sperm matured in his ducts, perhaps is a way to offer him better reproductive prospects with his partner.


One of the most intriguing findings of Dr Baker’s research relates to the quantity of sperm ejaculated; it offers not a mechanistic view but a teleologic one (based on final causes). Let the reader be reminded that final causes were excluded from scientific discourse by Enlightenment philosophers as being theological by nature, but they have come in full force again with Darwinian theory. In Dr Baker’s view, the volume of sperm ejaculated into the genital tract depends on what volume is necessary to ‘top up’ the woman, that is on the optimal volume needed in the context of sperm competition.

This has been a major surprise for me, especially because I had relied on a mechanistic view of ejaculation to describe routine sex as a female strategy to detect the man’s unfaithfulness (the theory is sketched in one of my published poems, in French). According to that view, which I will have no difficulty to discard if necessary, when a man and woman are engaged in routine sex, the woman’s interoceptive sense allows her to evaluate the volume ejaculated, which only depends (correcting for health states) on the time elapsed since last ejaculation. So, if these mates have had fairly regular intercourse twice a week, for instance, for weeks or months, there can be no way for the man to ejaculate outside his mate’s tract without her noticing it at the next intercourse, due to the unusually low volume then ejaculated. As a consequence, routine sex would be the woman’s demand, as a mate-guarding strategy.

Dr Baker proves me wrong on that point. If he is correct, the volume ejaculated inside a partner’s tract depends on two factors: 1/ time elapsed since last intercourse; and 2/ time spent together since last intercourse. If the partners spent most of the time together, the semen will be scarce because the man has little doubt of the woman’s faithfulness – his estimate of the chances that she cuckolded him is low, and accordingly he can be economical with his sperm. On the contrary, if they have been separated for a long time, his doubts about possible sperm competition will be raised, and the quantity ejaculated increased accordingly. So, the man ejaculates not the quantity that is available but the quantity that is optimal (with a view to facing sperm competition).

There is apparently a problem with the intuitive, mechanistic discharge model: Spermatic ducts are always full, sort of (SW 32). ‘Even the greatest rate of insemination (9.3 million sperm/h since last in-pair copulation when couples spend less than 25% of their time together) is lower than the estimated rate of sperm production by humans of 12.5 million/h (Johnson et al. 1980). It thus seems likely that observed insemination rates are in some ways strategic and not simply due to physiological constraint.’ (Baker & Bellis, SCH 166). This fact seems to imply some inconsistency in Dr Baker’s picture. As we saw in the previous paragraph, the man is willing to be economical with his sperm, because there would be an energetic trade-off implied. But does it make sense at all to talk of energetic costs of ejaculation, and of a trade-off, in such conditions of superabundant sperm production? In the normal use of the notion, a trade-off implies some scarcity, whereas we are faced here, seemingly, with such abundance that one cannot even talk, in the proper sense, of discharge nor of replenishing.

Moreover, given the trade-off, masturbatory ejaculates would be less abundant than copulatory ejaculates (Pound, Shackelford & Goetz, SCH 19), a fact that has been validated experimentally. The makeup of these different ejaculates would also be different: ‘The percentage of motile and morphologically normal sperm also is higher for copulatory ejaculates (Sofitikis & Miyagawa, 1993)’ (SCH 19). Given that, in Dr Baker’s view, morphologically normal sperm is made of ‘egg-getter sperm’, whereas ‘killer sperm’ displays other shapes, how is one to explain that there is more ‘egg-getters’ in a masturbatory ejaculate, when they can meet no egg?

Conception Via Sperm Warfare: The Figures

Under the present head, I have a slight problem with the figures advanced by Dr Baker. ‘A recent study in Britain concluded that 4 per cent of people are conceived via sperm warfare. In other words, one in every twenty-five owe their existence to the fact that their genetic father’s sperm out-competed the sperm from one or more other men within the reproductive tract of their mother.’ (SW 47). Elsewhere, Dr Baker considers this figure to be valid world wide: ‘Humans, with 4 per cent or more of children conceived via sperm warfare’ (SW 349).

Then, he also writes the following : ‘World wide, it has been calculated from studies of blood groups that about 10 per cent of children are in fact not sired by the man who thinks he is their father. This is also the level found in industrial Western societies.’ (SW 63-4), and: ‘Internationally, child support agencies are reporting a non-paternity rate of about 15 per cent.’ (SW 64), a figure he repetes elsewhere: ‘Of the men who resist supporting a child on the grounds of paternal uncertainty, 15 percent have their doubts verified by DNA fingerprinting.’ (SF 26). SF also confirms the 10 percent figure based on blood group studies. Dr Baker does not mention the 4 percent figure again in that book.

Let us stress that the number of people ‘conceived via sperm warfare’ must be higher than the number of people ‘not sired by the man who thinks he is their father’, because, among the former, there must be some who were sired by the man who thinks he is their father, that is to say sometimes the woman’s long-term partner, or husband, must have won the warfare and, even though he was cheated, that had no consequences on paternity issues. At least in some cases – even if Dr Baker shows that a woman is more likely to cheat on her partner while in estrus. So, a 4 percent figure of people ‘conceived via sperm warfare’ in a population hints at a lower number of people not sired by the putative father in that population, say 3 percent. Given the 10 percent figure from blood group studies, there cannot be a world wide 4 percent figure of people conceived via sperm warfare, because 10 percent of people not sired by the putative father hints, in turn, at a higher figure for sperm warfare, not a lower one.

Lastly, it must be stressed that the 10 percent figure is not an indicator of women’s unfaithfulness, which must be higher than that, because cheating does not always lead to pregnancy, presumably.

A way to reconcile these figures would be to state that British women are much less promiscuous than women in the world at large – 3-4 percent vs 10 percent. In this way John Stuart Mill would be proven wrong when he attributes our judgments on women to prejudice: ‘An Oriental thinks that women are by nature peculiarly voluptuous … An Englishman usually thinks that they are by nature cold. The sayings about women’s fickleness are mostly of French origin.’ (The Subjection of Women). As far as French women are concerned, a Frenchman is not so blinded by prejudice when he considers them to be fickle (souvent femme varie…), because more than 10 percent of them cheat on their legitimate partners, whereas an Englishman may have some reasons to say English women are cold, as sperm warfare is seemingly much less frequent among them.


Mainstream biology has been proven wrong by the sperm competition model in one important respect. Biologists relied on a model of ‘differential parental investment’ which they believed entitled them to conclude that men are promiscuous and women monogamous. Dr Robert L. Smith has pointed out that such view lacked consistency: ‘The biological irony of the double standard is that males could not have been selected for promiscuity if historically females denied them opportunity for expression of the trait. If strict monogamy were the singular human female mating strategy, then only rape would place ejaculates in position to compete and the potential role of sperm competition as a force in human evolution would be substantially diminished.’ (SCH 68).

It leads us to the model I call, from a graphic word used by Dr Baker, the ‘springboard model’: ‘Once a woman has a long-term partner, the costs of one-off intercourse are reduced as long as her infedility remains undetected. Her long-term relationship provides a springboard from which to exploit the genetic benefits of one-off sex with selected men without risking too much. She does not have this freedom, however, if she does not have a partner.’ (SW 260-1)

According to this model, a woman is not much interested in one-off sex while single, because she may end up with a pregnancy and no male support to help her bear the burden. As a single woman she is in search of a lasting relationship, and this can easily lead one to think women are monogamous. However, once she is engaged in a lasting relationship, the ‘springboard’ is provided for extra-pair or one-off sex, with which she may improve her reproductive success with mates whose genes appeal to her. As a single person, the woman seeks a partner, and her choice relies on status more than good looks; if need be, she will sacrifice the latter. As an engaged person, she seeks lovers and genetic endowment (BW 131). The genetic traits in favor have been described under the head ‘Clear Eyes’ (see above); important notions here are testosteronization (pretty obvious) and low fluctuating asymmetry (a mark of sound genetic endowment).

The broad outlines of the model being given, some details seem to border on inconsistency. If BW 131 is correct (‘In choosing a short-term partner for sex … looks are much more important’), the following needs some explanation: ‘Some men have a higher chance of being cuckolded than others, and it is those of low wealth and status that fare worst. … Moreover, the men most likely to cuckold the lower-status males are those of higher status.’ (BW 44-5) Both statements (BW 131 and BW 44-5) are rather intuitive, I should say, but still they do not fit quite well, taken together. Why short-term lovers – the men who cuckold other men – are mostly of high status, when high status is what is demanded of a long-term partner? Even if all women cannot have a high-status long-term partner, what benefits does one-off sex with a high-status man provide them with? Material benefits of some sorts, perhaps, but what about the genetic benefits implied in the springboard model? Or is it compulsory sex, with pressure being exerted by a socially dominant individual on a socially dominated individual? Similarly, it is not clear why women partnered with high-status men would not be likely to cuckold them with low-status men if the latter possess the required genetic endowment. Dr Baker explains that these women have much to lose if their unfaithfulness is detected, but that means, then, that sacrificing good looks while choosing a long-term partner is detrimental, because in reality the springboard is not even provided.

As we will see later, extra-pair sex with a high-status man also involve an important negative effect for low-status families (see ‘Optimizing vs Maximizing’).

One way to interpret these findings is to assume that high status and genetic endowment are correlated. In alleged ‘meritocracies’, this certainly makes sense, except that the relationship between male beauty and capacity is far from obvious and, in the above list of favored genetic traits, some are intellectual and no doubt contribute to status, while others seem to be completely independent from social capacity.


Most homosexuals are bisexual: ‘The vast majority (80 per cent) of those who have sex with men also have sex with women’ (SW 284) and, according to Dr Baker, they reproduce fairly well, somewhat better, in fact, than heterosexual men. This means that, among the 10 percent of children not sired by the man who thinks he is the biological father (see ‘Conceptions Via Sperm Warfare’), a good deal were sired by bisexual homosexuals, and this, in turn, supplies the clue as to the major engine of the prejudice against homosexuals. Dr Baker has provided part of the explanation with respect to that prejudice by stating that homosexuals are perceived to be significant carriers of sexually transmitted diseases. This implies that they are perceived as being especially prone to promiscuity, and I contend that the basis of the prejudice lies on this latter notion. In fact, monogamous men are prejudiced against all promiscuous men, and if another group, beside homosexuals, were perceived to be promiscuous, then individuals from that group too would be prejudiced against.

It is not simply ideology. I believe people are indifferent, that is tolerant, toward anybody whose behavior does not affect them in any way, even if they do not share their ideas nor understand their way of life; if they are not affected, they simply shrug shoulders. But in the case of promiscuity a monogamous man is at risk. He may have to raise a child not his own, and raising a child is not simply an idea, it means sweat and blood.

One may contend that genes are not the important thing in raising a family, that it is transmitting one’s values that matters, and that people adopting children of different genetic makeups are proof enough of it. Adoption is certainly worth mentioning in that respect, but on the other hand it is known that foster children and children of recomposed families suffer much more abuse, rape, and murder at the hands of their caretakers, with whom they are not related genetically, than biological children at the hands of their biological parents. It is my prediction that, with the development of the reproduction technologies described by Dr Baker in Sex in the Future, adoption will progressively disappear. What will remain is benevolent adoption of babies from deprived or chaotic countries or environments, by well-off parents who already have biological children, but people who cannot reproduce through intercourse will favor technologies that ensure they can raise children of their own genetic makeups, when these technologies become available.

The prejudice against gay men, and promiscuous men, will end as soon as paternity uncertainty ends, with the generalization of paternity tests. Pro-gay rights legislations passed in Western countries, like gay marriage, gay adoption, etc, tend, in the meantime, to tame bisexual gays in ways of life more acceptable to the monogamous citizen – or at least are intended as make-believe.


In relative terms, rapes conduct more often to pregnancy than routine intercourse. Various hypotheses are discussed by Dr Baker as to the possible reasons, but there is one element he does not discuss, which should make rape much less likely to lead to pregnancy, contrary to the data: ‘Insufficient lubrication prior to coitus, as in rape, may result in trauma to the vaginal wall with the discharge of blood into the vaginal cavity. Blood serum contains the spermatotoxic protein gamma globulin and often sperm antibodies as well.’ (Robert L. Smith, SCH 105). The reasons that make rape relatively more prolific must be powerful enough to counterbalance these chemical hindrances – and such powerful agency by necessity must entail some strong evolutionary benefits, otherwise it would not have developed as a powerful agency in the first place.


Whereas in BW Dr Baker contends that modern societies ‘are rapidly becoming, probably the most puritanical and repressive of all’ (BW 235), he has this to say in his introduction to the 2006 edition of SW: ‘The current batch of American under-thirties has even been branded ‘Generation Porn’. Sex is everywhere, from Web to television, and it would be encouraging to think that it reflects or at least precedes the development of the healthy, informed, and nonjudgmental attitude that Sperm Wars is intended to promote.’ (SW xxiii). Although this is more the expression of a wish, it seems that, in the meantime, Dr Baker has decided to take things at face value.

There is no reason to think that a ‘Generation Porn’ would be endowed with more healthy attitudes toward sex than the preceding ‘Generations Bordello’, and Dr Baker must be aware that a great number of serious studies have dealt with the many unhealthy aspects of pornography.

Although I believe that censorship is hardly enforcable in mass media societies (I do not even believe it is enforced, with respect to pornography, in regimes like China, and I am told, also, that it is not difficult for a Westerner to find child pornography, although it is prohibited), I see nothing healthy about the genre. Pornography was first legalized in Denmark in the 1960s, at a time when the Danish government was headed by a clergyman. This brave man was convinced, in his deepest inner self, based on what evidence I wonder, that prohibition was the problem and that, once legalized, pornography would cease to appeal to anyone. I am making fun of this man but it is not fair because pornography was legalized in every Western country shortly thereafter, clergymen or not, and this has more to do with the nature of mass media as an externalized central nervous system (McLuhan) than with anything else – but this is not the subject either. As to the clergyman’s or similar ideas, here is what Dr Dolf Zillmann has to say: ‘The finding of growing boredom, in contrast, seems in conflict not only with the increasing commercial success of pornography (a success attesting to insatiable interest) but with theoretical considerations also … Massive exposure to standard erotic fare fosters acceptance of not-so-standard forms of pornography. Massive exposure to coital scenes led to diminished reactions of repulsion to sadomasochistic activities and acts of bestiality.’ (Connections Between Sexuality and Aggression, 1998).

Interestingly, Dr Baker provides the following figures concerning prostitution: ‘In the United States in the 1940s, 60 percent of men had inseminated a prostitute at least once in their lives by the time they were about fifity. In the UK in the 1990s, 10 percent of men had paid for sex at least once in their lives by the time they were about fifty.’ (SF 279-80). Although the figures are taken from two different countries, if we assume similar conditions in both, they indicate a sharp decline. Clearly, prostitution has receded, and it has not been replaced by more healthy attitudes toward sex, but rather by the ‘commercial success of pornography’.

Dr Baker’s views on another phenomenon should have prevented him, I think, to ever express positive appreciations of videotaped pornography. As a biologist, he knows that in nature the viewing of copulation triggers copulation readiness; the instinctual message is: ‘When you see copulation, take immediate action toward copulation.’ He explains it in the context of sperm competition. Now, what happens in movie theaters, when people are exposed to sex scenes (as is well known, they have become utterly banal)? The excitation is repressed, energy cannot be released, the spectator stays quiet and silent. The public is compelled to remain impassive in presence of excitatory stimuli. This is what I call silver-screen conditioning. The message is: ‘When you see copulation, do not make a move.’ (It is important to note that the difference between real life and media is immaterial; as Reeves and Nass have shown, ‘the media equation’ is ‘real life = media’. This is another occurrence of an evolved trait turned odd in our society; see ‘Penis Shape and Size’.)

It is the same with hardcore pornography when viewed in groups. The boys just sit and watch, perhaps exchanging a few words. When they consume pornography alone in their bedrooms, it is for masturbatory purposes; then the message becomes: ‘When you see copulation, beat off.’ I do not perceive any likelihood of better reproductive stamina in any of these instances.

A last word on erotica consumption. It is assumed, since Kinsey, to be men only. Recent studies, however, report identical excitatory responses in men and women (Zillmann). Maybe one day we will find that women never ever turned their back to pornography when alone. I believe that the puzzling variety of answers across questionnaires about women’s behavior is one dimension of what Dr Baker calls ‘female crypsis’.

Optimizing vs Maximizing

At first sight, the demographic transition undergone by Western countries these last decades, with incipient population decline, runs contrary to the idea that people are genetically programmed to enhance their reproductive success. Discarding family planning and contraception as the causes of this shift, for, according to him, such practices have existed from time immemorial, Dr Baker outlines a history of humanity in three stages. In their condition of hunter-gatherers, humans lived in small nuclear families, and it is only with the advent of agrarian societies and a carbohydrate-rich diet inducing massive rates of infant death, that families expanded, both as a way to compensate the death toll and to get more hands for the manual work in the fields. With the advent of new technologies, nuclear families would return to former small sizes: ‘The reduction in family size to the levels found in modern industrial societies was not due to improved contraceptive technology, but to women subconsciously planning smaller and smaller families in response to the improved survival prospects of their children.’ (BW 141).

Dr Baker explains this in more detail with a distinction between maximizing and optimizing the number of one’s offspring. Typically, an individual projects himself on the next two generations, children and grand-children. It is not clever to make many children if they cannot be oferred survival conditions that ensure they get a fairly good number of offspring themselves, die too young, or contract disabling diseases, or become vagrants, and so on. Dr Baker tells us the fictional story of two women from a similar social background growing up as friends in the same environment. One made more children than the other, but in the next generation she was the loser because her children did not fare as well as her friend’s. The former maximized the number of her children, and she losed, the latter optimized that number, and she won. All this is very nice, but it deserves further review.

Dr Baker believes that world population will stabilize in the future when people learn to optimize, rather than maximize, the number of their children, that is when their survival prospects are improved. He states that the average number of children will be two – the magic number that is to stabilize world population. Such optimism I deem unfounded, as things are.

If material conditions are the one factor on which depends the reproductive success of one’s children, as Dr Baker seems to imply (for instance, he is saying nowhere that the number of parents at two individuals puts an upper limit to the optimum, although he writes that being a single parent is a disadvantage), people who can offer greater material conditions to the children they raise, will make more children, insofar as it raises their own reproductive success without impairing the reproductive success of their offspring. In other words, if the optimum number of children for a middle-income couple is two, the optimum number for a couple earning twice that income, able to proffer double wealth and material conditions to their children, would be (assuming, provisionally, a linear function) four. On the lower side of the scale, people are then expected to make no more than one child, and deprived people to make no children at all because they cannot provide them with material conditions worth the name.

As to deprived people, their tendency is to make many children, and this has been the case from the remotest antiquity. The word ‘proletarian’ derives from the Latin proles, which means ‘offspring’; the proletarians are those who make many children – and we do not call proletarians the rich, in spite of Dr Baker. It is not necessarily because poor people do not understand how to use condoms or cannot control their sexual urges, although these defects certainly are to be taken into consideration. When a woman is hopeless as to her prospects and cannot expect bright days in the future unless a miracle takes place, then she might be willing to maximize the number of her children anyway, and place them ‘in the hand of God’ (this is a metaphor I use: she does not have to be a believer), because, mind the logic, a miracle is more likely to occur for one out of x children than for one children alone. This is what Dr Baker calls low survival prospects, but we see such low prospects in the midst of rich nations, with a so-called underclass of unemployable people on the increase everywhere.

Furthermore, when a high-status man impregnates a low-status woman (see ‘Cuckoldry’), he contributes to widening the gap between the actual and optimum number of children in this family. Taking no financial responsibility for his act, he impairs the future prospects of these children. Even if a high-status male multiplies ad infinitum the number of such extra-pair children, it does not improve his reproductive success in regard to the number of children he is raising. If below optimum, it remains so, and his female partner bears the consequences: she fails to reach her optimum.

Several studies tend to show that high-status families are below reproductive optimum. In fact, this has been the contention of many scholars since Galton’s, and as Dr Baker must know of these studies I am surprised he is not discussing them, since they run contrary to his own predictions. In his book Dysgenics (2011), Dr Richard Lynn provides a table (by Lynn & Harvey, 2008) with fertility rates and IQ by country for year 2000, showing an inverse relationship between number of children and IQ at international level. Whether IQ measurements are relevant in the discussion I do not decide, but I perceive a robust correlation between these IQ measurements and GDPs, so there would be also an inverse relationship between fertility and wealth. Worse-off individuals and nations make more children than better-off; this must involve some consequences upon the survival prospects of all.

Promiscuity and Culture

Optimizing rather than maximizing may require some insight connected with genetic endowment, and so it cannot be expected to occur, in the absence of compulsion or incentive, in the population as a whole.

Insight may also lead some people – males – to evaluate uncertainty, and its cost, associated with the parenting effort that would be required of them, as too great, and consequently to relinquish all attempts at paternity (some others, only at parenting). There is a trade-off here, which has been finely expressed by Ferdinand Lundberg and Marynia F. Farnham, who, although they make allegiance to the exploded psychoanalytic school and have, besides, remained inconspicuous names, deserve to be quoted: ‘The cultural formula is: In proportion as one has children, all other things being equal, one will be handicapped in the competitive struggle for ego recognition, prestige and economic well-being. The psychic formula, however, is: In proportion as one feels oneself unable to have children, for whatever reason, one is handicapped in obtaining psychic gratification and general psychic stability.’ (Modern Woman. The Lost Sex, 1947).

It exists, I contend, a relationship between culture and promiscuity, but not with the causal direction usually thought of. It is not culture that debases mores, as claimed by philosophers like Ibn Khaldun or Rousseau, it is debased mores that enrich culture, because, with increased paternity uncertainty, more males relinquish all efforts associated with procreation. Where women are tightly controlled, males are relatively sure about paternity, and culture does not progress.

November 2015


  1. florentboucharel


    Under the head ‘Optimizing vs Maximizing’ I have misstated one of Dr Baker’s ideas. I wrote, in parentheses, that according to him a single parent is at a disadvantage. What he says, in fact, is that, although the data show that single mothers’ children fare less well, the cause has nothing to do with singleness, but with material conditions, and that single parents with financial means do no worse than couples having the same means.

    My misstatement being corrected, I would like to add that one more view of Dr Baker’s allows me to buttress another of my points. Under the same head ‘Optimizing vs Maximizing’, I have attempted to cast doubt on his optimism as to world population stability in the future. Assuming there is no upper limit to reproductive optimum, and that as long as social classes exist there will be different reproductive optima, I have written that a population poise supposes that the lowest classes make no children. The case, however, is even worse because, as Dr Baker shows, a single child is not even an option, for no one. A single child strategy is not viable, for if something happens all is lost. The lowest number of children for a woman (for a couple, if you like) is two. In consequence, the average number required for equilibrium is the same as the lowest possible number. Such conditions make a poise most unlikely, I should think.

    (Years ago, when I happened to be, shortly, a student in economics, a professor tried to explain to his students – who had asked nothing – why it was rational to make only one child. He explained that he could spend more on his child’s head and thus offer him greater material conditions and prospects. I thought the same as Dr Baker then, that his was a very risky strategy, but of course I kept it to myself, because it would have been grim to hint at accidents occurring to his child – besides, he may have resented being contradicted. However, as he was making his point, he looked at me, and he must have perceived my incredulity, and resented it, because at the end of the session he scored my essay rather meanly. He was one of several economics luminaries I have had the chance to meet in my life, another one being a professor who wondered aloud why old people saved money; he had just no idea.)

    Florent Boucharel

  2. florentboucharel

    With Dr Baker’s permission, here is his reply, which he sent me just before I published the comment above (Nov 26). I am grateful to him for his attention.

    Dear Florent

    Wow! I never expected a treatise of that length! It is very gratifying though to know that my books gave you so much food for thought and the motivation to put those thoughts down in writing. I appreciate that your main incentive was to point out what you consider errors in my logic and to put me straight, but that’s fine by me. I’m sure you won’t be surprised though if I say I still stick to my original viewpoints.

    I’m afraid I cannot possibly answer your points one-by-one. I have a book deadline to meet and need all the writing time I can get. So I’m going to take the easy way out. Most of the problems you raised Mark Bellis and I did consider during our early working out of human sperm competition and I think you’ll find they have been addressed in one or other of my/our books and early papers. In fact, most of our arguments along with tables, diagrams and references are in the academic book – HUMAN SPERM COMPETITION – on which Sperm Wars and Baby Wars are based. Everything there is presented in much greater detail.

    After years of wrangling with the publishers of the hardback version we last year gained the rights to publish this book in a cheap digital form. If you are interested, the link on French Amazon is


    As just one example from the many points in your blog covered in that book, the following is the way we reconciled a 4% conception rate via sperm competition with a 10% non-paternity:

    “8.4.1 What proportion of children are the result of sperm competition?

    “Another way of approaching the question of the pay-off to sperm competition via live births is to examine the frequency with which children are not the genetic offspring of their putative father (= cuckoldry; = paternal discrepancy).

    “Medical students are usually taught that the level of paternal discrepancy is 10-15% (Macintyre and Sooman, 1992). The figure of 10% is most widely used in DNA studies and is quoted in standard genetics textbooks. As Macintyre and Sooman (1992) point out, however, rather few of these studies have been published in any detail and there is a real need for proper investigation using modern techniques. A number of estimates of paternal discrepancy are given in Box_8.4 together with a brief discussion of some of the problems associated with such investigations.

    “Estimated levels range from a low of 1.4% for Caucasians in Michigan, USA, and 2% for the !Kung to a high of around 30%. In Britain, values range from about 6% in a large urban community in London to around 30% for the inhabitants of tower blocks of flats in both northwest and southern England.

    “Of course, paternal discrepancy should equal EPC rate, not double-mating rate. Not all EPCs are double-matings (i.e. within 5 days of the last or next insemination by the female’s primary partner). According to our survey, only about 50% (Box_8.3) of EPCs not involving contraception during the fertile phase of the cycle are double-matings leading to sperm competition. This suggests that approximately 50% of all cases of paternal discrepancy in Britain are children conceived to the sperm of an extra-pair male after competition with sperm from the primary male partner.

    “If we take the most conservative measure of paternal discrepancy for Britain (6%; Box_8.4), which is also the one based on the largest sample, we obtain a figure for children conceived to the extra-pair male following sperm competition of about 3%. However, this should be an underestimation of the incidence of sperm competition for in addition to occasions on which the EPC male wins, there should be other occasions on which the IPC male wins. It is tempting simply to double the figure of 3% (to 6%) on the grounds that EPC and IPC males have equal chances of winning. This, however, is not necessarily the case.
    8.4.2 Which male does best: first or last, extra-pair or in-pair?

    “One of the few clear conclusions so far to emerge from studies of sperm competition in other animals is that which male wins is not random but depends very much on mating sequence and time interval between matings. In insects, with the exception of for example bees and silkmoths, the last male to mate with the female before her eggs begin to travel down her oviduct invariably has by far the greatest probability of fertilization (Parker, 1970a). That the same is true for birds was first noticed by Aristotle about 2300 years ago (Payne and Kahrs, 1961) and has since been well established (Birkhead and Møller, 1992). For example, the proportion of eggs fertilized by the last male to mate with the female ( = P2) is about 80% for the dung fly, Scatophaga stercoraria (Parker, 1970b) and 70-80% for the zebra finch, Taeniopygia guttata (Birkhead et al, 1989). Across species in birds, the figure is relatively constant at about 80% (Birkhead and Møller, 1992). The precise figure, however, is influenced by the time interval between matings.

    “Generally, studies of the chicken, turkey, mallard and zebra finch show that last male precedence is the rule if copulations are separated by 4 h or more. If the copulation interval is less than this, paternity is proportional to the number of sperm inseminated by each male (see review by Birkhead and Møller, 1992).

    “Mammals show a much less clear-cut influence of mating order. The first male to mate has the advantage in house mice, the last male in prairie voles, with no clear order effects in laboratory rats or deer mice (Dewsbury, 1984). Equally, there were no order effects with swine. In most cases, however, much depended on the time interval between first and second males as it does for birds.

    “In mice, if the time interval is very short (minutes), the second copulation seems to be spiteful and the female may not conceive at all (section 6.4.1). Thereafter, as time interval increases, the proportion of eggs fertilized by the first male increases. Longer time intervals also favour the first male in hamsters, Mesocricetus auratus (Huck et al., 1985). In 13-lined ground squirrels, Spermophila tridecemlineatus, short time intervals swing paternity strongly in favour of one or other male, medium time intervals in favour of mixed paternity, and longer time intervals in favour of the first male. Success of the second male depended critically on the length of copulation (Schwagmeyer and Foltz, 1990).

    “Poultry breeders have long interpreted the second male advantage shown by birds in terms of stratified sperm storage (see review by Birkhead and Møller, 1992). Females are receptive well in advance of ovulation and the sperm are stored in blind-ended storage organs. Sperm from later males could thus be nearer the entrance (and thus nearer the exit) than sperm from earlier males. On a ‘last in, first out’ principle, storage organs could promote a second male advantage. However, recent but limited empirical evidence provides no support for the stratification model and Birkhead and Møller (1992) suggest that limited sperm storage coupled with some form of sperm displacement may be a better explanation. This is similar to the explanation preferred for insects (Ridley, 1989; Parker et al., 1990; Rothschild, 1991).

    “Whatever the eventual explanation for the fairly consistent pattern of mating precedence in birds and insects, it seems clear that there can be no simple story for the much more variable outcome in mammals. This outcome probably depends on some variable interaction between sperm number (Chapter 9), sperm removal (Chapter 6), and sperm fertilizing capacity (Chapter 12) as well as on a variety of female influences ranging from sperm retention (Chapter 10) to selective sperm passage through the female tract (Chapter 4).

    “Female humans are continually receptive and sperm are fertile (5 days) and alive (8-10 days) a lot longer than the optimum time from insemination to fertilization (2 days). The scope for sperm-sperm and female-male interactions in influencing the outcome is considerable. Essentially, however, we have as yet no idea for humans or other primates whether there is a first or last male advantage, if either. Our prediction would be that in humans, all else being equal, it is the last male to inseminate a female near to 2 days before ovulation who has the advantage.

    “Even given an asymmetry between males depending on mating sequence, the relative probability of fertilization by EPC and IPC males may depend on the number of sperm they each ejaculate (Chapter 9) and the number of sperm from each that the female retains (Chapter 10). We have already given some indication that the female may favour the EP male through her differential use of contraception (sections 8.3.3 and 8.3.4). She may also favour the extra-pair male in her timing of EPCs and IPCs relative to the timing of ovulation (Box_6.10). In Chapter 10, we present evidence that the female may even favour the EP male via the relative number of sperm she retains from each.

    “Given the possibility that EP males may have a higher probability of fertilization during sperm competition, we may not be justified in calculating the proportion of children conceived via sperm competition by simply doubling 3% to obtain 6%. The figure may be lower (but more than 3%). For the moment, however, we shall be conservative and assume a figure of only 4%.

    “Both our Nationwide survey, therefore, and blood group studies, suggest that over the last few decades in Britain at least 4% of children (but perhaps as many as 6-12%) have been conceived to a sperm that has prevailed in sperm competition. In other words, in any group of 25 people, at least one owes their existence to the fact that their father’s ejaculate had the characteristics necessary to outcompete that of another male. Such a level of reproductive pay-off is relatively hefty in evolutionary terms. In Britain, at the present time, therefore, sperm competition is still a major source of selection on the human sexual programme. Whether the figure is higher or lower in other communities elsewhere remains to be determined.”

    And I think you’ll find an equally detailed discussion of most of the points you raise.

    One of your points I do need to address here: your discussion of ‘clear eyes’ in attractiveness. One or other of us has misinterpreted the meaning of clear eyes by the original researchers. This was not our work. We took it from the literature and it never occurred to us that the authors might mean iris pigmentation because, as you say, it makes no sense. We assumed (and maybe the authors say – I can’t remember) that ‘clear eyes’ referred to the eye-whites and the clear membranes such as the conjunctiva. These make much more sense as a measure of health. Similarly, the skin pigmentation work you refer to is again not mine and I don’t remember (but these days my memory isn’t perfect) ever quoting it.

    I hope this and HUMAN SPERM COMPETITION answers a few of your points, but I don’t expect to convince you on them all.

    Best wishes


  3. florentboucharel

    The skin pigmentation quote alluded to by Dr Baker at the end of his reply is from Randy Thornhill. To avoid doubt, I have just added all the authors’ names when quoting the collective work “Sperm Competition in Humans,” which is more conform to standard quotation practice.

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