Donald Symons’ ‘The Evolution of Human Sexuality’: A Founding Work of Modern Evolutionary Psychology

The Evolution of Human Sexuality by Donald Symons (Oxford University Press 1980). 

Research over the last four decades in the field that has come to be known as evolutionary psychology has focused disproportionately on mating behaviour. Geoffrey Miller (1998) has even argued that it is the theory of sexual selection rather than that of natural selection which, in practice, guides most research in this field. 

This does not reflect merely the prurience of researchers. Rather, given that reproductive success is the ultimate currency of natural selection, mating behaviour is, perhaps along with parental investment, the form of behaviour most directly subject to selective pressures.

Almost all of this research traces its ancestry ultimately to Donald Symons’ ‘The Evolution of Human Sexuality’ by Donald Symons. Indeed, much of it was explicitly designed to test claims and predictions formulated by Symons himself in this very book.

Age Preferences 

For example, in his discussion of the age at which women are perceived as most attractive by males, Symons formulated two alternative hypotheses. 

First, if human evolutionary history were characterized by fleeting one-off sexual encounters (i.e. one-night standscasual sex and hook-ups), then, he reasoned, men would have evolved to find women most attractive when the latter are at the age of their maximum fertility

For women, fertility is said to peak around when a woman reaches her mid-twenties since, although women still in their teens have high pregnancy rates, they also experience greater risk of birth complications

However, if human evolutionary history were characterized instead by long-term pair bonds, then men would have evolved to be maximally attracted to somewhat younger women (i.e. those at the beginning of their reproductive careers), so that, by entering a long-term relationship with the woman at this time, a male is potentially able to monopolize her entire lifetime reproductive output (p189). 

More specifically, males would have evolved to prefer females, not of maximal fertility, but rather of maximal reproductive value, a term borrowed from demography and population genetics which refers to a person’s expected future reproductive output given their current age. Unlike fertility, a woman’s reproductive value peaks around her mid- to late-teens.  

On the basis of largely anecdotal evidence, Symons concludes that human males have evolved to be most attracted to females of maximal reproductive value rather than maximal fertility.  

Subsequent research designed to test between Symons’s rival hypotheses has largely confirmed his speculative hunch that it is younger females in their mid- to late-teens who are perceived by males as most attractive (e.g. Kenrick and Keefe 1992). 

Why Average is Attractive 

Symons is also credited as the first person to recognize that a major criterion of attractiveness is, paradoxically, averageness, or at least the first to recognize the significance of, and possible evolutionary explanation for, this discovery.[1] Thus, Symons argues that: 

“[Although] health and status are unusual in that there is no such thing as being too healthy or too high ranking… with respect to most anatomical traits, natural selection produces the population mean” (p194). 

On this view, deviations from the population mean are interpreted as the result of deleterious mutations or developmental instability, and hence bad genes.[2]

Concealed Ovulation

Support has even emerged for some of Symons’ more speculative hunches. 
 
For example, one of Symons’ two proposed scenarios for the evolution of concealed ovulation, in which he professed “little confidence” (p141), was that this had evolved so as to impede male mate-guarding and enable females select a biological father for their offspring different from their husbands (p139-141). 
 
Consistent with this theory, studies have found that women’s mate preferences vary throughout their menstrual cycle in a manner compatible with a so-called ‘dual mating strategy’, preferring males evidencing a willingness to invest in offspring at most times, but, when at their most fertile, preferring characteristics indicative of genetic quality (e.g. Penton-Voak et al 1999). 

Meanwhile, a questionnaire distributed via a women’s magazine found that women engaged in extra-marital affairs do indeed report engaging in ‘extra-pair copulations’ (EPCs) at times likely to coincide with ovulation (Bellis and Baker 1990).[3]

The Myth of Female Choice

Interestingly, Symons even anticipated some of the mistakes evolutionary psychologists would be led into. 
 
Thus, he warns that researchers in modern western societies may be prone to overestimate the importance of female choice as a factor in human evolution, because, in their own societies, this is a major factor, if not the major factor, in determining marriage and sexual and romantic relationships (p203).[4]
 
However, in ancestral environments (i.e. what evolutionary psychologists now call the Environment of Evolutionary Adaptedness or EEA) arranged marriages were likely the norm, as they are in most premodern cultures around the world today (p168).[5] 
 
Thus, Symons concludes: 

“There is no evidence that any features of human anatomy were produced by intersexual selection [i.e. female choice]. Human physical sex differences are explained most parsimoniously as the outcome of intrasexual selection (the result of male-male competition)” (p203). 

Thus, human males have no obvious analogue of the peacock’s tail, but they do have substantially greater levels of upper-body strength and violent aggression as compared to females.[6]
 
This was a warning almost entirely ignored by subsequent generations of researchers before being forcefully reiterated by Puts (2010)

Homosexuality as a ‘Test-Case 

An idea of the importance of Symons’s work can be ascertained by comparing it with contemporaneous works addressing the same subject-matter. 
 
Edward O Wilson’s  On Human Nature was first published in 1978, only a year before Symons’s ‘The Evolution of Human Sexuality’. 

However, whereas Symons’s book set out much of the theoretical basis for what would become the modern science of evolutionary psychology, Wilson’s chapter on “Sex” has dated rather less well, and a large portion of chapter is devoted to introducing a now faintly embarrassing theory of the evolution of homosexuality which has subsequently received no empirical support (see Bobrow & Bailey 2001).[7] 
 
In contrast, Symons’s own treatment of homosexuality is innovative. It is also characteristic of his whole approach and illustrates why ‘The Evolution of Human Sexuality‘ has been described by David Buss as “the first major treatise on evolutionary psychology proper” (Handbook of Evolutionary Psychology: p251). 
 
Rather than viewing all behaviours as necessarily adaptive (as critics of evolutionary psychology, such as Stephen Jay Gould, have often accused sociobiologists of doing),[8] Symons instead focuses on admittedly non-adaptive (or, indeed, even maladaptive) behaviours, not because he believes them to be adaptive, but rather because they provide a unique window on the nature of human sexuality.
 
Accordingly, Symons does not concern himself with how homosexuality evolved, implicitly viewing it as a rare and maladaptive malfunctioning of normal sexuality. Yet the behaviour of homosexuals is of interest to Symons because it provides a window on the nature of male and female sexuality as it manifests itself when freed from the constraints imposed by the conflicting desires of the opposite sex. 
 
On this view, the rampant promiscuity manifested by many homosexual men (e.g. cruising and cottaging in bathhouses and public lavatories, or Grindr hookups) reflects the universal male desire for sexual variety when freed from the constraints imposed by the conflicting desires of women. 

This desire for sexual variety is, of course, obviously reproductively unproductive among homosexual men themselves. However, it evolved because it enhanced the reproductive success of heterosexual men by motivating them to attempt to mate with multiple females and thereby father multiple offspring. 
 
In contrast, burdened with pregnancy and lactation, women’s potential reproductive rate is more tightly constrained than that of men. They therefore have little to gain reproductively by mating with multiple males, since they can usually gestate, and nurse, only one offspring at a time. 
 
It is therefore notable that, among lesbians, there is little evidence of the sort of rampant promiscuity common among gay men. Instead, lesbian relationships seem to be characterized by much the same features as heterosexual coupling (i.e. long-term pair-bonds).
 
The similarity of heterosexual coupling to that of lesbians, and the striking contrast with that of male homosexuals, suggests that it is women, not men, who exert decisive influence in dictating the terms of heterosexual coupling.[9] 
 
Thus, Symons reports:

There is enormous cross-cultural variation in sexual customs and laws and the extent of male control, yet nowhere in the world do heterosexual relations begin to approximate those typical of homosexual men This suggests that, in addition to custom and law, heterosexual relations are structured to a substantial degree by the nature and interests of the human female” (p300). 

This conclusion is, of course, diametrically opposite to the feminist contention that it is men who dictate the terms of heterosexual coupling and for whose exclusive benefit such relationships are structured. 
 
It also suggests, again contrary to feminist assumptions of male dominance, that most men are ultimately frustrated in achieving their sexual ambitions to a far greater extent than are most women. 

Thus, Symons concludes: 

The desire for sexual variety dooms most human males to a lifetime of unfulfilled longing” (p228). 

Here, Symons anticipates Camille Paglia who was later to famously observe: 

Men know they are sexual exiles. They wander the earth seeking satisfaction, craving and despising, never content. There is nothing in that anguished motion for women to envy” (Sexual Personae: p19). 

Criticisms of Symons’s Use of Homosexuality as a Test-Case

There is, however, a potential problem with Symons’s use of homosexual behaviour as a window onto the nature of male and female sexuality as they manifest themselves when freed from the conflicting desires of the opposite sex. The whole analysis rests on a questionable premise – namely that homosexuals are, their preference for same-sex partners aside, otherwise similar, if not identical, to heterosexuals of their own sex in their psychology and sexuality. 
 
Symons defends this assumption, arguing: 

There is no reason to suppose that homosexuals differ systematically from heterosexuals in any way other than their sexual object choice” (p292). 

Indeed, in some respects, Symons seems to see even “sexual object choice” as analogous among homosexuals and heterosexuals of the same sex. 
 
For example, he observes that, unlike women, both homosexual and heterosexual men tend to evaluate prospective mates primarily on the basis their physical appearance and youthfulness (p295). 

Thus, in contrast to the failure of periodicals featuring male nudes to attract a substantial female audience (see below), Symons notes the existence of a market for gay pornography parallel in most respects to heterosexual porn – i.e. featuring young, physically attractive models in various states of undress (p301). 
 
This, of course, contradicts the feminist notion that men are led to ‘objectify’ women only due to the sexualized portrayal of the latter in the media. 
 
Instead, Symons concludes: 

That homosexual men are at least as likely as heterosexual men to be interested in pornography, cosmetic qualities and youth seems to me to imply that these interests are no more the result of advertising than adultery and alcohol consumption are the result of country and western music” (p304).[10] 

However, this assumption of the fundamental similarity of heterosexual and homosexual male psychology has been challenged by David Buller in his book, Adapting Minds: Evolutionary Psychology and the Persistent Quest for Human Nature
 
Buller cites evidence that male homosexuals are ‘feminized’ in many aspects of their behaviour.

For example, one recent study found that male homosexuals have more female-typical occupation interests than do heterosexual males (Ellis & Ratnasingam 2012).

Thus, one of the few consistent early correlates of homosexuality is gender non-conformity in childhood and some evidence (e.g. digit ratios, the fraternal birth order effect) has been interpreted to suggest that the level of prenatal exposure to masculinizing androgens (e.g. testosterone) in utero affects sexual orientation (see Born Gay: The Pyschobiology of Sexual Orientation).

As Buller notes, although gay men seem, like heterosexual men, to prefer youthful sexual partners, they also appear to prefer sexual partners who are, in other respects highly masculine.[11]

Thus, Buller observes: 

“The males featured in gay men’s magazines embody very masculine, muscular physiques, not pseudo-feminine physiques” (Adapting Minds: p227).

Indeed, the models in such magazines seem in most respects similar in physical appearance to the male models, pop stars, actors and other ‘sex symbols’ and celebrities fantasized about by heterosexual women and girls.
 
How then are we to resolve this apparent paradox? 
 
One possible explanation that some aspects of the psychology of male homosexuals are feminized but not others – perhaps because different parts of the brain are formed at different stages of prenatal development, at which stages the levels of masculinizing androgens in the womb may vary. 
 
Indeed, there is even some evidence that homosexual males may be hyper-masculinized in some aspects of their physiology.

For example, it has been found that homosexual males report larger penis-sizes than heterosexual men (Bogaert & Hershberger 1999). 
 
This, researchers Glenn Wilson and Qazi Rahman propose, may be because: 

If it is supposed that the barriers against androgens with respect to certain brain structures (notably those concerned with homosexuality) lead to increased secretion in an effort to break through, or some sort of accumulation elsewhere… then there may be excess testosterone left in other departments” (Born Gay: The Psychobiology of Sex Orientation: p80). 

Another possibility is that male homosexuals actually lie midway between heterosexual men and women in their degree of masculinization.  

On this view, homosexual men come across as relatively feminine only because we naturally tend to compare them to other men (i.e. heterosexual men). However, as compared to women, they may be relatively masculine, as reflected in the male-typical aspects of their sexuality focused upon by Symons. 
 
Interestingly, this latter interpretation suggests the slightly disturbing possibility that, freed from the restraints imposed by women, heterosexual men would be even more indiscriminately promiscuous than their homosexual counterparts.

Evidence consistent with this interpretation is provided by one study from the 1980s which found that, when approached by a female stranger (also a student), on a University campus, with a request to go to bed with them, fully 72% of male students agreed (Clark and Hatfield 1989). 

In contrast, in the same study, not a single one of the 96 females approached by male strangers with the same request on the same university campus agreed to go to bed with the male stranger.

Yet what percentage of the female students subsequently sued the university for sexual harassment was not reported.

Pornography as a “Natural Experiment

For Symons, fantasy represents another window onto sexual and romantic desires. Like homosexuality, fantasy is, by its very nature, unconstrained by the conflicting desires of the opposite sex (or indeed by anything other than the imagination of the fantasist). 

Symons later collaborated in an investigation into sexual fantasy by means of a questionnaire (Ellis and Symons 1990). 

However, in the present work, he investigates fantasy indirectly by focusing on what he calls “the natural experiment of commercial periodical publishing” – i.e. pornographic magazines (p182). 
 
In many respects, this approach is preferable to a survey because, even in an anonymous questionnaire, individuals may be less than honest when dealing with a sensitive topic such as their sexual fantasies. On the other hand, they are unlikely to regularly spend money on a magazine unless they are genuinely attracted by its contents. 
 
Before the internet age, softcore pornographic magazines, largely featuring female nudes, commanded sizeable circulations. However, their readership (if indeed ‘readership’ is the right words, since there was typically little reading involved) was almost exclusively male. 
 
In contrast, there was little or no female audience for magazines containing pictures of naked males. Instead, magazines marketed towards women (e.g. fashion magazines) contain, mostly, pictures of other women. 
 
Indeed, when, in the 1970s, attempts were made, in the misguided name of feminism and ‘women’s liberation’, to market magazines featuring male nudes to a female readership, one such title, Viva, abandoned publishing male nudes after just a few years due to lack of interest or demand, then subsequently went bust just a few years after that, while the other, Playgirl, although it did not entirely abandon male nudes, was notorious, as a consequence, for attracting a readership composed in large part of homosexual men. 
 
Symons thus concludes forcefully and persuasively: 

The notion must be abandoned that women are simply repressed men waiting to be liberated” (p183). 

Indeed, though it has been loudly and enthusiastically co-opted by feminists, this view of women, and of female sexuality – namely women as “repressed men waiting to be liberated” – represents an obviously quintessentially male viewpoint. 

Indeed, taken to extremes, it has even been used as a justification for rape.

Thus, the curious, sub-Freudian notion that female rape victims actually secretly enjoy being raped seems to rest ultimately on the assumption that female sexuality is fundamentally the same as that of men (i.e. indiscriminately enjoying of promiscuous sex) and that it is only women’s sexual ‘repression’ that prevents them admitting as much.

Romance Literature 

Unfortunately, however, there is notable omission in Symons’s discussion of pornography as a window into male sexuality – namely, he omits to consider whether there exists any parallel artistic genre that offers equivalent insight into the female psyche. 
 
Later writers on the topic have argued that romance novels (e.g. Mills and Boon, Jane Austin), whose audience is as overwhelmingly female as pornography’s is male, represent the female equivalent of pornography, and that analysis of the the content of such works provides insights into female mate preferences parallel to those provided into male psychology by pornography (e.g. Kruger et al 2003; Salmon 2004; see also Warrior Lovers: Erotic Fiction, Evolution and Female Sexuality, co-authored by Symons himself). 

Female Orgasm as Non-Adaptive

An entire chapter of ‘The Evolution of Human Sexuality’, namely Chapter Three (entitled, “The Female Orgasm: Adaptation or Artefact”), is devoted to rejecting the claim that the female orgasm represents a biological adaptation. 
 
This is perhaps excessive. However, it does at least conveniently contradicts the claim of some critics of evolutionary psychology, and of sociobiology, such as Stephen Jay Gould that the field is ‘ultra-Darwinian’ or ‘hyper-adaptionist’ and committed to the misguided notion that all traits are necessarily adaptive.[12]
 
In contrast, Symons champions the thesis that the female capacity for orgasm is a simply non-adaptive by-product of the male capacity to orgasm, the latter of which is of course adaptive. 
 
On this view, the female orgasm (and clitoris) is, in effect, the female equivalent of male nipples (only more fun). 
 
Certainly, Symons convincingly critiques the romantic notion, popularized by Desmond Morris among others, that the female orgasm functions as a mechanism designed to enhance ‘pair-bonding’ between couples. 
 
However, subsequent generations of evolutionary psychologists have developed less naïve models of the adaptive function of female orgasm. 
 
For example, Geoffrey Miller argues that the female orgasm functions as an adaptation for mate choice (The Mating Mind: p239-241). 
 
Of course, at first glance, experiencing orgasm during coitus may appear to be a bit late for mate choice, since, by the time coitus has occurred, the choice in question has already been made. However, given that, among humans, most sexual intercourse is non-reproductive (i.e. does not result in conception), the theory is not altogether implausible. 
 
On this view, the very factors which Symons views as suggesting female orgasm is non-adaptive – such as the relative difficultly of stimulating female orgasm during ordinary vaginal sex – are positive evidence for its adaptive function in carefully discriminating between suitors/lovers to determine their desirability as father for a woman ’s offspring. 
 
Nevertheless, at least according to the stringent criteria set out by George C Williams in his classic Adaptation and Natural Selection, as well as the more general principle of parsimony (also known as Occam’s Razor), the case for female orgasm as an adaptation remains unproven (see also Sherman 1989; Case Of The Female Orgasm: Bias in the Science of Evolution).

Out-of-Date?

Much of Symons’ work is dedicated to challenging the naïve group-selectionism of Sixties ethologists, especially Desmond Morris. Although scientifically now largely obsolete, Morris’s work still retains a certain popular resonance and therefore this aspect of Symons’s work is not entirely devoid of contemporary relevance. 
 
In place of Morris‘s rather idyllic notion that humans are a naturally monogamous ‘pair-bonding’ species, Symons advocates instead an approach rooted in the individual-level (or even gene-level) selection championed Richard Dawkins in The Selfish Gene (reviewed here). 
 
This leads to some decidedly cynical conclusions regarding the true nature of sexual and romantic relations among humans. 
 
For example, Symons argues that it is adaptive for men to be less sexually attracted to their wives than they are to other women – because they are themselves liable to bear the cost of raising offspring born to their wives but not those born to other women with whom they mate (e.g. those mated to other males). 
 
Another cynical conclusion is that the primary emotion underlying the institution of marriage, both cross-culturally and in our own society, is neither love nor even lust, but rather male sexual jealousy and proprietariness (p123). 

Marriage, then, is an institution borne not of love, but of male sexual jealousy and the behaviour known to biologists as mate-guarding
 
Meanwhile, in his excellent chapter on ‘Copulation as a Female Service’ (Chapter Eight), Symons suggests that many aspects of heterosexual romantic relationships may be analogous to prostitution
 
As well as its excessive focus on debunking sixties ethologists like Morris, ‘The Evolution of Human Sexuality’ is also out-of-date in a more serious respect Namely, it fails to incorporate the vast amount of empirical research on human sexuality from a sociobiological perspective which has been conducted since the first publication of his work. 
 
For a book first published thirty years ago, this is inevitable – not least because much of this empirical research was inspired by Symons’ own ideas and specifically designed to test theories formulated in this very work. 
 
In addition, potentially important new factors in human reproductive behaviour that even Symons did not foresee have been identified, for example role of levels of fluctuating asymmetry functioning as a criterion for, or at least correlate of, physical attractiveness. 
 
For an updated discussion of the evolutionary psychology of human sexual behaviour, complete with the latest empirical data, readers should consult the latest edition of David Buss’s The Evolution Of Desire: Strategies of Human Mating
 
In contrast, in support of his theories Symons relies largely on classical literary insight, anecdote and, most importantly, a review of the ethnographic record. 
 
However, this latter focus ensures that, in some respects, the work remains of more than merely of historical interest. 
 
After all, one of the more legitimate criticisms levelled against recent research in evolutionary psychology is that it is insufficiently cross-cultural and, with several notable exceptions (e.g. Buss 1989), relies excessively on research conducted among convenience samples of students at western universities. 
 
Given costs and practicalities, this is inevitable. However, for a field that aspires to understand a human nature presumed to be universal, such a method of sampling is highly problematic. 
 
The Evolution of Human Sexuality’ therefore retains its importance for two reasons. 

First, is it the founding work of modern evolutionary psychological research into human sexual behaviour, and hence of importance as a landmark and classic text in the field, as well as in the history of science more generally. 

Second, it also remains of value to this day for the cross-cultural and ethnographic evidence it marshals in support of its conclusions. 

Endnotes

[1] Actually, the first person to discover this, albeit inadvertently, was the great Victorian polymath, pioneering statistician and infamous eugenicist Francis Galton, who, attempting to discover abnormal facial features possessed by the criminal class, succeeded in morphing the faces of multiple convicted criminals. The result was, presumably to his surprise, an extremely attractive facial composite, since all the various minor deformities of the many convicted criminals whose faces he morphed actually balanced one another out to produce a face with few if any abnormalities or disproportionate features.

[2] More recent research in this area has focused on the related concept of fluctuating asymmetry.

[3] However, recent meta-analyses have called into question the evidence for cyclical fluctuations in female mate preferences (Wood et al 2014; cf. Gildersleeve et al 2014), and it has been suggested that such findings may represent casualties of the so-called replication crisis in psychology. It has also been questioned whether ovulation in humans is indeed concealed, or is actually detectable by subtle cues (e.g. Miller et al 2007), for example, changes in face shape (Oberzaucher et al 2012), breast symmetry (Scutt & Manning 1996) and body scent (Havlicek et al 2006).

[4] Another factor leading recent researchers to overestimate the importance of female choice in human evolution is their feminist orientation, since female choice gives women an important role in human evolution, even, paradoxically, in the evolution of male traits.

[5] Actually, in most cultures, only a girl’s first marriage is arranged on her behalf by her parents. Second- and third-marriages are usually negotiated by the woman herself. However, since female fertility peaks early, it is a girl’s first marriage that is usually of the most reproductive, and hence Darwinian, significance.

[6] Indeed, the human anatomical trait in humans that perhaps shows the most evidence of being a product of intersexual selection is a female one, namely the female breasts, since the latter are, unlike the mammary glands of most other mammals, permanently present from puberty on, not only during lactation, and composed primarily of fatty tissues, not milk (Møller 1995; Manning et al 1997; Havlíček et al 2016

[7] Wilson terms his theory “the kin selection theory hypothesis of the origin of homosexuality” (p145). However, a better description might be the ‘helper at the nest theory of homosexuality’, the basic idea being that, like sterile castes in some insects, and like older siblings in some bird species where new nest sites are unavailable, homosexuals, rather than reproducing themselves, direct their energies towards assisting their collateral kin in successfully raising, and provisioning, their own offspring (p143-7). The main problem with this theory is that there is no evidence that homosexuals do indeed devote any greater energies towards assisting their kin in this respect. On the contrary, homosexuals instead seem to devote much of their time and resources towards their own sex life, much as do heterosexuals (Bobrow & Bailey 2001).

[8] As we will see, contrary to the stereotype of evolutionary psychologists as viewing all traits as necessarily adaptive, as they are accused of doing by the likes of Gould, Symons also argued that the female orgasm and menopause are non-adaptive, but rather by-products of other adaptations.

[9] This is not necessarily to say that rampant, indiscriminate promiscuity is a male utopia, or the ideal of any man, be he homosexual or heterosexual. On the contrary, the ideal mating system for any individual male is harem polygyny in which the chastity of his own partners is rigorously policed (see Despotism and Differential Reproduction: which I have reviewed here and here). However, given an equal sex ratio, this would condemn other males to celibacy. Similarly, Symons reports that “Homosexual men, like most people, usually want to have intimate relationships”. However, he observes:

Such relationships are difficult to maintain, largely owing to the male desire for sexual variety; the unprecedented opportunity to satisfy this desire in a world of men, and the male tendency towards sexual jealousy” (p297).  

It does indeed seem to be true that homosexual relationships, especially those of gay males, are, on average, of shorter duration than are heterosexual relationships. However, Symons’ claim regarding “the male tendency towards sexual jealousy” is questionable. Actually, subsequent research in evolutionary psychology has suggested that men are no more prone to jealousy than women, but rather that it is sorts of behaviours which most intensely provoke such jealousy that differentiate the sexes (Buss 1992). However, many gay men practice open relationships, which seems to suggest a lack of jealousy – or perhaps this simply reflects a recognition of the difficulty of maintaining relationships given, as Symons puts it, “the male desire for sexual variety [and] the unprecedented opportunity to satisfy this desire in a world of men”. 

[10] Indeed, far from men being led to objectify women due to the portrayal of women in a sexualized manner in the media, Symons suggests:

There may be no positive feedback at all; on the contrary, constant exposure to pictures of nude and nearly nude female bodies may to some extent habituate men to these stimuli” (p304).

[11] Admittedly, some aspects of body-type typically preferred by gay males (especially the twink) do reflect apparently female traits, especially a relative lack of body-hair. However, lack of body-hair is also obviously indicative of youth. Moreover, a relative lack of body-hair also seems to be a trait favoured in men by heterosexual women. For a discussion of the relative preference on the part of (heterosexual) females for masculine versus feminine traits in male sex partners, see the final section of this review.

[12] Incidentally, Symons also rejects the theory that the female menopause is adaptive, a theory which has subsequently become known as the grandmother hypothesis (p13). Also, although it does not directly address the issue, Symons’ discussion of human rape (p276-85), has also been interpreted as implicitly favouring the theory that rape is a by-product of the greater male desire for commitment free promiscuous sex, rather than the product of a specific rape adaptation in males (see Palmer 1991; and A Natural History of Rape: reviewed here). 

References 

Bellis & Baker (1990). Do females promote sperm competition?: Data for humans. Animal Behavior, 40: 997-999 
Bobrow & Bailey (2001). Is male homosexuality maintained via kin selection? Evolution and Human Behavior, 22: 361-368 
Bogaert & Hershberger (1999) The relation between sexual orientation and penile size. Archives of Sexual Behavior 1999 Jun;28(3) :213-21. 
Buss (1989). Sex differences in human mate preferences: Evolutionary hypotheses tested in 37 cultures. Behavioral and Brain Sciences 12: 1-49
Ellis & Ratnasingam (2012) Gender, Sexual Orientation, and Occupational Interests: Evidence of Androgen Influences. Mankind Quarterly  53(1): 36–80
Ellis & Symons (1990) Sex differences in sexual fantasy: An evolutionary psychological approach, Journal of Sex Research 27(4): 527-555.
Gildersleeve, Haselton & Fales (2014) Do women’s mate preferences change across the ovulatory cycle? A meta-analytic review. Psychological Bulletin 140(5):1205-59.
Havlíček, Dvořáková, Bartos & Fleg (2006) Non‐Advertized does not Mean Concealed: Body Odour Changes across the Human Menstrual Cycle. Ethology 112(1):81-90.
Havlíček et al (2016) Men’s preferences for women’s breast size and shape in four cultures. Evolution and Human Behavior 38(2): 217–226 
Kenrick & Keefe (1992). Age preferences in mates reflect sex differences in human reproductive strategies. Behavioral and Brain Sciences, 15: 75-133. 
Kruger et al (2003) Proper and Dark Heroes as Dads and Cads. Human Nature 14(3): 305-317 
Manning et al (1997) Breast asymmetry and phenotypic quality in women. Ethology and Sociobiology 18(4): 223–236 
Miller (1998). How mate choice shaped human nature: A review of sexual selection and human evolution. In C. Crawford & D. Krebs (Eds.), Handbook of Evolutionary Psychology: Ideas, Issues, and Applications (pp. 87-129). Mahwah, NJ: Lawrence Erlbaum
Miller, Tybur & Jordan (2007). Ovulatory cycle effects on tip earnings by lap dancers: economic evidence for human estrous? Evolution and Human Behavior. 28(6):375–381 
Møller et al (1995) Breast asymmetry, sexual selection, and human reproductive success. Ethology and Sociobiology 16(3): 207-219 
Palmer (1991) Human Rape: Adaptation or By-Product? Journal of Sex Research 28(3): 365-386 
Penton-Voak et al (1999) Menstrual cycle alters face preferences, Nature 399 741-2. 
Puts (2010) Beauty and the Beast: Mechanisms of Sexual Selection in Humans. Evolution and Human Behavior 31 157-175 
Salmon (2004) The Pornography Debate: What Sex Differences in Erotica Can Tell Us About Human Sexuality. In Evolutionary Psychology, Public Policy and Personal Decisions (London: Lawrence Erlbaum Associates, 2004) 
Scutt & Manning (1996) Symmetry and ovulation in women. Human Reproduction 11(11):2477-80
Sherman (1989) The clitoris debate and levels of analysis, Animal Behaviour, 37: 697-8
Wood et al (2014). Meta-analysis of menstrual cycle effects on women’s mate preferencesEmotion Review, 6(3), 229–249.

Judith Harris’s ‘The Nurture Assumption’: By Parent or Peers

Judith Harris, The Nurture Assumption: Why Children Turn Out the Way They Do. Free Press, 1998.

Almost all psychological traits on which individual humans differ, from personality and intelligence to mental illness, are now known to be substantially heritable. In other words, individual differences in these traits are, at least in part, a consequence of genetic differences between individuals. 

This finding is so robust that it has even been termed by Eric Turkenheimer the First Law of Behviour Genetics and, although once anathema to most psychologists save a marginal fringe of behavioural geneticists, it has now, under the sheer weight of evidence produced by the latter, belatedly become the new orthodoxy. 

On reflection, however, this transformation is not entirely a revelation. 

After all, it was only in the mid-twentieth century that the curious notion that individual differences were entirely the product of environmental differences first arose, and, even then, this delusion was largely restricted to psychologists, sociologists, feminists and other such ‘professional damned fools’, along with those among the semi-educated public who seek to cultivate an air of intellectualism by aping the former’s affections. 

Before then, poets, peasants and laypeople alike had long recognized that ability, insanity, temperament and personality all tended to run in families, just as physical traits like stature, complexion, hair and eye colour also do.[1]

However, while the discovery of a heritable component to character and ability merely confirms the conventional wisdom of an earlier age, another behavioural genetic finding, far more surprising and counterintuitive, has passed relatively unreported. 

This is the discovery that the so-called shared family environment (i.e. the environment shared by siblings, or non-siblings, raised in the same family home) actually has next to no effect on adult personality and behaviour. 

This we know from such classic study designs in behavioural genetics as twin studiesadoption studies and family studies.  

In short, individuals of a given degree of relatedness, whether identical twins, fraternal twins, siblings, half-siblings or unrelated adoptees, are, by the time they reach adulthood, no more similar to one another in personality or IQ when they are raised in the same household than when they are raised in entirely different households. 

The Myth of Parental Influence 

Yet parental influence has long loomed large in virtually every psychological theory of child development, from the Freudian Oedipus complex and Bowby’s attachment theory to the whole literary genre of books aimed at instructing anxious parents on how best to raise their children so as to ensure that the latter develop into healthy, functional, successful adults. 

Indeed, not only is the conventional wisdom among psychologists overturned, but so is the conventional wisdom among sociologists – for one aspect of the shared family environment is, of course, household income and social class

Thus, if the family that a person is brought up in has next to no impact on their psychological outcomes as an adult, then this means that the socioeconomic status of the family home in which they are raised also has no effect. 

Poverty, or a deprived upbringing, then, has no effect on IQ, personality or the prevalence of mental illness, at least by the time a person has reached adulthood.[2]

Neither is it only leftist sociologists who have proved mistaken. 

Thus, just as leftists use economic deprivation as an indiscriminate, catch-all excuse for all manner of social pathology (e.g. crime, unemployment, educational underperformance) so conservatives are apt to place the blame on divorcefamily breakdown, having children out of wedlock and the consequential increase in the prevalence of single-parent households

However, all these factors are, once again, part of the shared family environment – and according to the findings of behavioural genetics, they have next to no influence on adult personality or intelligence. 

Of course, chaotic or abusive family environments do indeed tend to produce offspring with negative life outcomes. 

However, none of this proves that it was the chaotic or abusive family environment that caused the negative outcomes. 

Rather, another explanation is at hand – perhaps the offspring simply biologically inherit the personality traits of their parents, the very personality traits that caused their family environment to be so chaotic and abusive in the first place.[3] 

For example, parents who divorce or bear offspring out-of-wedlock likely differ in personality from those who first get married then stick together, perhaps being more impulsive or less self-disciplined and conscientious (e.g. less able refrain from having children from a relationship that was destined to be fleeting, or less able to persevere and make the relationship last). 

Their offspring may, then, simply biologically inherit these undesirable personality attributes, which then themselves lead to the negative social outcomes associated with being raised in single-parent households or broken homes. The association between family breakdown and negative outcomes for offspring might, then, reflect simply the biological inheritance of personality. 

Similarly, as leftists are fond of reminding us, children from economically-deprived backgrounds do indeed have lower recorded IQs and educational attainment than those from more privileged family backgrounds, as well as other negative outcomes as adults (e.g. lower earnings, higher rates of unemployment). 

However, this does not prove that coming from a deprived family background necessarily itself depresses your IQ, educational attainment or future salary. 

Rather, an equally plausible possibility is simply that offspring simply biologically inherit the low intelligence of their parents – the very low intelligence which was likely a factor causing the low socioeconomic status of their parents, since intelligence is known to correlate strongly with educational and occupational advancement.[4]

In short, the problem with all of this body of research which purports to demonstrate the influence of parents and family background on psychology and behavioural outcomes for offspring is that they fail to control for the heritability of personality and intelligence, an obvious confounding factor

The Non-Shared Environment

However, not everything is explained by heredity. As a crude but broadly accurate generalization, only about half the variation for most psychological traits is attributable to genes. This leaves about half of the variation in intelligence, personality and mental illness to be explained environmental factors.  

What are these environmental factors if they are not to be sought in the shared family environment

The obvious answer is, of course, the non-shared family environment – i.e. the ways in which even children brought up in the same family-home nevertheless experience different micro-environments, both within the home and, perhaps more importantly, outside it. 

Thus, even the fairest and most even-handed parents inevitably treat their different offspring differently in some ways.  

Indeed, among the principal reasons that parents treat their different offspring differently is precisely because the different offspring themselves differ in their own behaviour.  

Corporal punishment 

Rather than differences in the behaviour of different children resulting from differences in how their parents treat them, it may be that differences in how parents treat their children may reflect responses to differences in the behaviour of the children themselves. 

In other words, the psychologists have the direction of causation precisely backwards. 

Take, for example, one particularly controversial issue, namely the physical chastisement of children by their parents as a punishment for bad behaviour (e.g. spanking). 

Thus, some psychologists have sometimes argued that physical chastisement actually causes misbehaviour. 

As evidence, they cite the fact that children who are spanked more often by their parents or caregivers on average actually behave worse than those whose caregivers only rarely or never spank the children entrusted to their care.  

This, they claim, is because, in employing spanking as a form of discipline, caregivers are inadvertently imparting the message that violence is a good way of solving your problems. 

Actually, however, I suspect children are more than capable of working out for themselves that violence is often an effective means of getting your way, at least if you have superior physical strength to your adversary. Unfortunately, this is something that, unlike reading, arithmetic and long division, does not require explicit instruction by teachers or parents. 

Instead, a more obvious explanation for the correlation between spanking and misbehaviour in children is not that spanking causes misbehaviour, but rather that misbehaviour causes spanking. 

Indeed, once one thinks about it, this is in fact rather obvious: If a child never seriously misbehaves, then a parent likely never has any reason to spank that child, even if the parent is, in principle, a strict disciplinarian; whereas, on the other hand, a highly disobedient child is likely to try the patience of even the most patient caregiver, whatever his or her moral opposition to physical chastisement in principle. 

In other words, causation runs in exactly the opposite direction to that assumed by the naïve psychologists.[5] 

Another factor may also be at play – namely, offspring biologically inherit from their parents the personality traits that cause both the misbehaviour and the punishment. 

In other words, parents with aggressive personalities may be more likely to lose their temper and physically chastise their children, while children who inherit these aggressive personalities are themselves more likely to misbehave, not least by behaving in an aggressive or violent manner. 

However, even if parents treat their different offspring differently owing to the different behaviour of the offspring themselves, this is not the sort of environmental factor capable of explaining the residual non-shared environmental effects on offspring outcomes. 

After all, this merely begs the question as to what caused these differences in offspring behaviour in the first place? 

If the differences in offspring behaviour exist prior to differences in parental responses to this behaviour, then these differences cannot be explained by the differences in parental responses.  

Peer Groups 

This brings us back to the question of the environmental causes of offspring outcomes – namely, if about half the differences among children’s IQs and personalities are attributable to environmental factors, but these environmental factors are not to be found in the shared family environment (i.e. the environment shared by children raised in the same household), then where are these environmental factors to be sought? 

The search for environmental factors affecting personality and intelligence has, thus far, been largely unsuccessful. Indeed, some behavioural geneticists have almost gone as far as conceding scholarly defeat in identifying correlates for the environmental portion of the variance. 

Thus, leading contemporary behavioural geneticist Robert Plomin in his recent book, Blueprint: How DNA Makes Us Who We Are, concludes that those environmental factors that affect cognitive ability, personality, and the development of mental illness are, as he puts it, ‘unsystematic’ in nature. 

In other words, he seems to be saying that they are mere random noise. This is tantamount to accepting that the null hypothesis is true. 

Judith Harris, however, has a quite different take. According to Harris, environmental causes must be sought, not within the family home, but rather outside it – in a person’s interactions with their peer-group and the wider community.[6]

Environment ≠ Nurture 

Thus, Harris argues that the so-called nature-nurture debate is misnamed, since the word ‘nurture’ usually refers to deliberate care and moulding of a child (or of a plant or animal). But many environmental effects are not deliberate. 

Thus, Harris repeatedly references behaviourist John B. Watson’s infamous boast: 

Give me a dozen healthy infants, well-formed, and my own specified world to bring them up in and I’ll guarantee to take any one at random and train him to become any type of specialist I might select—doctor, lawyer, artist, merchant-chief and, yes, even beggar-man and thief, regardless of his talents, penchants, tendencies, abilities, vocations, and race of his ancestors.” 

Yet what strikes me as particularly preposterous about Watson’s boast is not its radical environmental determinism, nor even its rather convenient unfalsifiability.[7] 

Rather, what most strikes me as most preposterous about Watson’s claim is its frankly breath-taking arrogance. 

Thus, Watson not only insisted that it was environment alone that entirely determined adult personality. In this same quotation, he also proclaimed that he already fully understood the nature of these environmental effects to such an extent that, given omnipotent powers to match his evidently already omniscient understanding of human development, he could produce any outcome he wished. 

Yet, in reality, environmental effects are anything but clear-cut. Pushing a child in a certain direction, or into a certain career, may sometimes have the desired effect, but other times have the exact opposite effect to that desired, provoking the child to rebel against parental dictates. 

Thus, even to the extent that environment does determine outcomes, the precise nature of the environmental factors implicated, and their interaction with one another, and with the child’s innate genetic endowment, is surely far more complex than the simple mechanisms proposed by behaviourists like Watson (e.g. reinforcement and punishment). 

Language Acquisition 

The most persuasive evidence for Harris’s theory of the importance of peer groups comes from an interesting and widely documented peculiarity of language acquisition

The children of immigrants, whose parents speak a different language inside the family home, and may even themselves be monolingual, nevertheless typically grow up to speak the language of their host culture rather better than they do the language to which they were first exposed in the family home. 

Indeed, while their parents may never achieve fluency in the language of their host culture, having missed out on the Chomskian critical period for language acquisition, their children often actually lose the ability to speak their parent’s language, often much to the consternation of parents and grandparents. 

Yet, from an sociobiological or evolutionary psychological perspective, such an outcome is obviously adaptive. 

If a child is to succeed in wider society, they must master its language, whereas, if their parent’s first language is not spoken anywhere in their host society except in their family, then it is of limited utility, and, once their parents themselves become proficient in the language of the host culture, becomes entirely redundant (see The Ethnic Phenomenon (reviewed herehere and here): p258). 

Code-Switching 

Harris suggests that the same applies to personality. Just as the child of immigrants switches between one language and another at home and school, so they also adopt different personalities. 

Thus, many parents are surprised to be told by their children’s teachers at parents’ evenings that their offspring is quiet and well-behaved at school, since, as they themselves report, he or she isn’t at all like that at home. 

Yet, at home, a child has only, at most, a sibling or two with whom to compete for his parents’ attention. In contrast, at school, he or she has a whole class with whom to compete for their teacher’s attention.

It is therefore unsurprising that most children are less outgoing at school than they are at home with their parents. 

For example, an older sibling might be able push his little brother around at home. But, if he is small for his age, he is unlikely to be able to get away with the same behaviour among his peers at school. 

Children therefore adopt two quite different personalities – one for interactions with family and siblings, and another for among their peers.

This then, for Harris, explains why, perhaps surprisingly, birth-order has generally been found to have little if any effect on personality, at least as personality manifests itself outside the family home. 

An Evolutionary Theory of Socialization? 

Interestingly, even evolutionary psychologists have not been immune from the delusion of parental influence. Thus, in one influential paper, anthropologists Patricia Draper and Henry Harpending argued that offspring calibrate their reproductive strategy by reference to the presence or absence of a father in their household (Draper & Harpending 1982). 

On this view, being raised in a father-absent household is indicative of a social environment where low male parental investment is the norm, and hence offspring adjust their own reproductive strategy accordingly, adopting a promiscuous, low-investment mating strategy characterized by precocious sexual development and an inability to maintain lasting long-term relationships (Draper & Harpending 1982Belsky et al 1991). 

There is indeed, as these authors amply demonstrate, a consistent correlation between father-absence during development and both earlier sexual development and more frequent partner-switching in later life. 

Yet there is also another, arguably more obvious, explanation readily at hand to explain this association. Perhaps offspring simply inherit biologically the personality traits, including sociosexual orientation, of their parents. 

On this view, offspring raised in single-parent households are more likely to adopt a promiscuous, low-investment mating strategy simply because they biologically inherit the promiscuous sociosexual orientation of their parents, the very promiscuous sociosexual orientation that caused the latter to have children out-of-wedlock or from relationships that were destined to break down and hence caused the father-absent childhood of their offspring. 

Moreover, even on a priori theoretical grounds, Draper, Harpending and Belsky’s reasoning is dubious. 

After all, whether you personally were raised in a one- or two-parent family is obviously a very unreliable indicator of the sorts of relationships prevalent in the wider community into which you are born, since it represents a sample size of just one. 

Instead, therefore, it would be far more reliable to calibrate your reproductive strategy in response to the prevalence of one-parent households in the wider community at large, rather than the particular household type into which you happen to have been born.  

This, of course, directly supports Harris’s own theory of ‘peer group socialization’. 

In short, to the extent that children do adapt to the environment and circumstances of their upbringing (and they surely do), they must integrate into, adopt the norms of, and a reproductive strategy to maximize their fitness within, the wider community into which they are born, rather than the possibly quite idiosyncratic circumstances and attitudes of their own family. 

Absent Fathers, from Upper-Class to Under-Class 

Besides language-acquisition among the children of immigrants, another example cited by Harris in support of her theory of ‘peer group socialization’ is the culture, behaviours and upbringing of British upper-class males.

Here, boys were, and, to some extent, still are, reared primarily, not by their parents, but rather by nanniesgovernoresses and, more recently, in exclusive fee-paying all-male boarding schools

Yet, despite having next to no contact with their fathers throughout most of their childhood, these boys nevertheless managed somehow to acquire manners, attitudes and accents similar, if not identical, to those of their upper-class fathers, and not at all those of the middle-class nannies, governoresses and masters with whom they spent most of their childhood being raised. 

Yet this phenomenon is by no means restricted to the British upper-classes. On the contrary, rather than citing the example of the British upper-classes in centuries gone by, Harris might just as well have cited that of contemporary underclass in Britain and elsewhere, since what was once true of the British upper-classes, is now equally true of the underclass

Just as the British upper-classes were once raised by governoresses, nannies and in private schools with next to no contact with their fathers, so contemporary underclass males are similarly raised in single-parent households, often to unwed mothers, and typically have little if any contact with their biological fathers. 

Here, as Warren Farrell observes in his seminal The Myth of Male Power (which I have reviewed here and here), there is a now a “a new nuclear family: woman, government and child”, what Farrell terms “Government as a Substitute Husband”. 

Yet, once again, these underclass males, raised by single parents with the assistance of the state, typically turn out much like their absent fathers with whom they have had little if any contact, often going on to promiscuously father a succession of offspring themselves, with whom they likewise have next to no contact. 

Abuse 

But what of actual abuse? Surely this has a long-term devastating psychological impact on children. This, at any rate, is the conventional wisdom, and questioning this wisdom is tantamount to contemporary heresy, with attendant persecution

Take, for example, what is perhaps the form of child abuse that provokes the most outrage and disgust – namely, sexual abuse. Here, it is frequently asserted that paedophiles were almost invariably themselves abused as children, which creates a so-called ‘cycle of abuse’. 

However, there are at least three problems with this claim. 

First, it cannot explain how the first person in this cycle became a paedophile. 

Second, we might doubt whether it is really true that paedophiles are disproportionately likely to have themselves been abused as children. After all, abuse is something that almost invariably happens surreptitiously ‘behind closed doors’ and is therefore difficult to verify or disprove. 

Thus, even if most paedophiles claim to have been victims of abuse, it is possible that they are simply lying in order to elicit sympathy or excuse or shift culpability for their own offending. 

Finally, even if paedophiles can be shown to be disproportionately likely to have themselves been victimized as children, this by no means proves that their victimization caused their sexual orientation. 

Rather, since most abuse is perpetrated by parents or other close family members, an alternative possibility is that victims simply biologically inherit the sexual orientation of their abuser. After all, if homosexuality is partially heritable, as is now widely accepted, then why not paedophilia as well? 

However, the finding that the shared family environment accounts for hardly any of the variance in outcomes among adults does not preclude the possibility that severe abuse may indeed have an adverse effect on adult outcomes. 

After all, adoption studies can only tell us what percent of the variance is caused by heredity or by shared or unshared environments within a specific population as a whole. 

Perhaps the shared family environment accounts for so little of the variance precisely because the sort of severe abuse that does indeed have a devastating long-term effect on personality and mental health is, thankfully, so very rare in modern societies. 

Indeed, it may be especially rare within the families used in adoption studies precisely because adoptive families are carefully screened for suitability before being allowed to adopt. 

Moreover, Harris emphasizes an important caveat: Even if abuse does not have long-term adverse psychological effects, this does not mean that abuse causes no harm, and nor does it in any way excuse such abuse. 

On the contrary, the primary reason we shouldn’t mistreat children (and should severely punish those who do) is not on account of some putative long-term psychological effect on the adults whom the children subsequently become, but rather because of the very real pain and suffering inflicted on a child at the time the abuse takes place. 

Race Differences in IQ 

Finally, Harris even touches upon that most vexed area of the (so-called) nature-nurture debate – race differences in intelligence

Here, the politically-correct claim that differences in intelligence between racial groups, as recorded in IQ tests, are of purely environmental origin runs into a problem, since the sorts of environmental effects that are usually posited by environmental determinists as accounting for the black-white test score gap in America (e.g. differences in rates of poverty and socioeconomic status) have been shown to be inadequate because, even after controlling for these factors, there remains a still unaccounted for gap in test-scores. 

Thus, as Arthur R. Jensen laments: 

This gives rise to the hypothesizing of still other, more subtle environmental factors that either have not been or cannot be measured—a history of slavery, social oppression, and racial discrimination, white racism, the ‘black experience,’ and minority status consciousness [etc]” (Straight Talk About Mental Tests: p223). 

The problem with these explanations, however, is that none of these factors has yet been demonstrated to have any effect on IQ scores. 

Moreover, some of the factors proposed as explanations are formulated in such a vague form (e.g. “white racism, the ‘black experience’”) that it is difficult to conceive of how they could ever be subjected to controlled testing in the first place.[8] 

Jensen has termed this mysterious factor the ‘X-factor’. 

In coining this term, Jensen was emphasizing its vague, mysterious and unfalsifiable nature. Jensen did not actually believe that this posited ‘X-factor’, whatever it was, really did account for the test-score gap. Rather, he thought heredity explained most, if not all, of the remaining test-score gap. 

However, Harris takes Jensen at his word. Thus, she announces: 

I believe I know what this X factor is… I can describe it quite clearly. Black kids and white kids identify with different groups that have different norms. The differences are exaggerated by group contrast effects and have consequences that compound themselves over the years. That’s the X factor” (p248-9). 

Interestingly, although she does not develop it, Harris’s claim is actually compatible with, and potentially reconciles, the conflicting findings of two of the most widely-cited studies in this vexed area of research and debate. 

First, in the more recent of these two studies, Minnesota Transracial Adoption Study, the same differences in IQ were observed among black, white and mixed-race children adopted into upper-middle class white families as are found among the respective among black, white and mixed-race populations in society at large (Scarr & Weinberg 1976). 

Moreover, although, when tested during childhood, the children’s adoptive households did seem to have had a positive effect on their IQ scores, by the time they reached the cusp of adulthood, the black teenagers who had been adopted into upper-middle-class white homes actually scored no higher in IQ than did blacks in the wider population not raised in upper-middle class white families (Weinberg, Scarr & Waldman 1992). 

This study is often cited by hereditarians as evidence for innate racial differences (e.g. Levin 1994Lynn 1994Whitney 1996). 

However, in the light of the findings of the behavioural genetics studies discussed by Harris in ‘The Nurture Assumption’, the fact that white upper-middle-class adoptive homes had no effect on the adult IQs of the black children adopted into them is, in fact, hardly surprising. 

After all, as we have seen, the shared family environment generally has no effect on IQ, at least by the time the person being tested has reached adulthood. One would therefore not expect adoptive homes, howsoever white and upper-middle-class, to have any effect on adult IQs of the black children adopted into them, or indeed of the white or mixed-race children adopted into them. 

In short, adoptive homes have no effect on adult IQ, whether or not the adoptees, or adoptive families, are black, white, brown, yellow, green or purple! 

But, if race differences in intelligence are indeed entirely environmental in origin, then where are these environmental causes to be found, if not in the family environment? 

Harris has an answer – black culture. 

According to her, the black adoptees, although raised in white adoptive families, nevertheless still come to identify as black, and to identify with the wider black culture and social norms. In addition, they may, on account of their racial identification, come to socialize with other blacks in school and elsewhere. 

As a result of this acculturation to African-American norms and culture, they therefore come to score lower in IQ than their white peers and adoptive siblings. 

But how can we test this theory? Perhaps we could look at the IQ scores of black children raised in white families where there is no wider black culture with which to identify, and few if any black peers with whom to socialize?  

This brings us to the second of the two studies which Harris’s theory potentially reconciles, namely the Eyferth study.  

Here, it was found that the mixed-race children fathered by black American servicemen who had had sexual relationships with German women during the Allied occupation of Germany after World War Two had almost exactly the same average IQ scores as a control group of offspring fathered by white US servicemen during the same time period (Eyferth 1959). 

The crucial difference from the Minnesota study may be that these children, raised in monoracial Germany in the mid-twentieth century, had no wider African-American culture with which to identify or whose norms to adopt, and few if any black or mixed-race peers in their vicinity with whom to socialize. 

This then is perhaps the last lifeline for the radical environmentalist theory of race differences in intelligence – namely the theory that African-American culture somehow depresses intelligence. 

Unfortunately, however, this proposition is likely almost as politically unpalatable to politically-correct liberals as is the notion that race differences in intelligence reflect innate genetic differences.[9] 

Endnotes

[1] Thus, this ancient wisdom is reflected, for example, in many folk sayings, such as the apple does not fall far from the tree, a chip off the old block and like father, like son, many of which long predate either Darwin’s theory of evolution, and Mendel’s work on heredity, let alone the modern work of behavioural geneticists.

[2] It is important to emphasize here that this applies only to psychological outcomes, and not, for example, economic outcomes. For example, a child raised by wealthy parents is indeed likely to be wealthier than one raised in poverty, if only because s/he is likely to inherit (some of) the wealth of his parents. It is also possible that s/he may, on average, obtain a better job as a consequence of the opportunities opened by his privileged upbringing. However, his IQ will be no higher than had s/he been raised in relative poverty, and neither will s/he be any more or less likely to suffer from a mental illness. 

[3] Similarly, it is often claimed that children raised in care homes, or in foster care, tend to have negative life-outcomes. However, again, this by no means proves that it is care homes or foster care that causes these negative life-outcomes. On the contrary, since children who end up in foster care are typically either abandoned by their biological parents, or forcibly taken from their parents by social services on account of the inadequate care provided by the latter, or sometimes outright abuse, it is obvious that their parents represent an unrepresentative sample of society as a whole. An obvious alternative explanation, then, is that the children in question simply inherit the dysfunctional personality attributes of their biological parents, namely the very dysfunctional personality attributes that caused the latter to either abandon their children or have them removed by the social services.

[4] Likewise, the heritability of such personality traits as conscientiousness and self-discipline, in addition to intelligence, likely also partly account for the association between parental income and academic attainment among their offspring, since both academic attainment, and occupational success, require the self-discipline to work hard to achieve success. These factors, again in addition to intelligence, likely also contribute to the association between parental income and the income and socioeconomic status ultimately attained by their offspring.

[5] This possibility could, of course, be ruled out by longitudinal studies, which investigate whether the spanking preceded the misbehaviour, or vice versa. However, this is easier said than done, since, unless relying on the reports by caregivers or children themselves, which depends on both the memory and honesty of the caregivers and children themselves, it would have to involve intensive, long-term, and continued observation in order to establish which came first, namely the pattern of misbehaviour, or the adoption of physical chastisement as a method of discipline. This would, presumably, require continuous observation from birth onwards, so as to ensure that the very first instance of spanking or excessive misbehaviour were recorded. To my knowledge, such a careful and intensive long-term study of this sort has yet to be conducted, if even it is possible.

[6] The fact that the relevant environmental variables must be sought outside the family home is one reason why the terms ‘between-family environment’ and ‘within-family environment’, sometimes used as synonyms or alternatives for ‘shared’ and ‘non-shared family environment’ respectively, are potentially misleading. Thus, the ‘within-family environment’ refers to those aspects of the environment that differ for different siblings even within a single family. However, these factors may differ within a single family precisely because they occur outside, not within, the family itself. The terms ‘shared’ and ‘non-shared family environment’ are therefore to be preferred, so as to avoid any potential confusion these alternative terms could cause.

[7] Both practical and ethical considerations, of course, prevent Watson from actually creating his “own specified world” in which to bring up his “dozen healthy infants”. Therefore, no one is able to put his claim to the test. It is therefore unfalsifiable and Watson is therefore free to make such boasts, safe in the knowledge that there is no danger of his actually being made to make good on his claims or being proven wrong.

[8] Actually, at least some of these theories are indeed testable and potentially falsifiable. With regard to the factors quoted by Jensen (namely, “a history of slavery, social oppression, and racial discrimination, white racism… and minority status consciousness”), one way of testing these theories is to look at test scores in those countries where there is no such history. For example, in sub-Saharan Africa, as well as in Haiti and Jamaica, blacks are not in the majority, and are moreover in control of the government. Yet the IQ scores of the indigenous population of Africa is actually even lower than among blacks in the USA (see Richard Lynn’s Race Differences in Intelligence: reviewed here). True, most such countries still have a history of racial oppression and discrimination, albeit in the form of European colonialism rather than racial slavery or segregation in the American sense. However, the lower scores for black Africans is true even in those few sub-Saharan African countries that were not colonized by western powers, or only briefly colonized (e.g. Ethiopia). Moreover, this merely begs the question as to why Africa was so easily colonized by Europeans. Also, other minority groups ostensibly subject to racial discrimination and oppression (e.g. Jews, Overseas Chinese) actually score very high in IQ, and are economically successful. As for “the ‘black experience’”, this meanly begs the question as to why the ‘black experience’ has been so similar, and resulted in the same low IQs, in so many different parts of the world, something implausible unless unless the ‘black experience’ itself reflects innate aspects of black African psychology. 

[9] Thus, ironically, the recently deceased James Flynn, though always careful, throughout his career, to remain on the politically-correct radical environmentalist side of the debate with regard to the causes of race differences in intelligence, nevertheless recently found himself taken to task by the leftist, politically-correct British Guardian newspaper for a sentence in his recent book, Does Your Family Make You Smarter, where he described American blacks as coming from a “from a cognitively restricted subculture” (Wilby 2016). Thus, whether one attributes lower black IQs to biology or to culture, either answer is certain offend leftists, and the power of political correctness can, it seems, never be appeased.

References 

Belsky, Steinberg & Draper (1991) Childhood Experience, Interpersonal Development, and Reproductive Strategy: An Evolutionary Theory of Socialization Child Development 62(4): 647-670 

Draper & Harpending (1982) Father Absence and Reproductive Strategy: An Evolutionary Perspective Journal of Anthropological Research 38:3: 255-273 

Eyferth (1959) Eine Untersuchung der Neger-Mischlingskinder in WestdeutschlandVita Humana, 2, 102–114 

Levin (1994) Comment on Minnesota Transracial Adoption Study. Intelligence. 19: 13–20 

Lynn, R (1994) Some reinterpretations of the Minnesota Transracial Adoption Study. Intelligence. 19: 21–27 

Scarr & Weinberg (1976) IQ test performance of black children adopted by White familiesAmerican Psychologist 31(10):726–739 

Weinberg, Scarr & Waldman, (1992) The Minnesota Transracial Adoption Study: A follow-up of IQ test performance at adolescence Intelligence 16:117–135 

Whitney (1996) Shockley’s experiment. Mankind Quarterly 37(1): 41-60

Wilby (2006) Beyond the Flynn effect: New myths about race, family and IQ? Guardian, September 27.