Natural selection and future sex

Genes dictate our looks, may define our character and so may influence our fate. John Turner reviews four books with some disconcerting ideas.

The Telmah (or Hamlet-backwards) hypothesis postulates, pace Shakespeare, that "there is a DNA rough-hews our ends, re-shape them how we will". Dean Hamer and Peter Copeland in Living with Our Genes state it clearly: genes build brains, brains through their balance of neural transmitters make temperament, and a person's temperament - through interaction with and modification by the environment - generates his or her character and behaviour. Genes therefore both set a norm for the human species and, along with experience and environment, generate variation about that norm. Nancy Etcoff in Survival of the Prettiest points up the deep division between this theory and the orthodox "standard social sciences model": that the human mind is a tabula rasa within which all behaviour is culturally conditioned or environmentally induced.

The rigorous approach to the Telmah model taken by Hamer and Copeland is to plot the physico-chemical action of identified neurotransmitters in the brain, and then the significance for individual behaviour of genetic variants in the control of the transmitters. The strongest cases they make are for the temperamental traits called "harm avoidance" (anxiety, depression, shyness and obsession), manifested throughout life and strongly influenced by innate variations in the functioning of serotonin in the brain; and "novelty seeking", likewise influenced by the metabolism of dopamine. People affected by the short form of the serotonin transporter gene are statistically marked for life as a shy, cranky toddler and as a Eeyore in adulthood. The evidence is more circumstantial for aggression, addiction, ageing, intelligence and weight control, and for sexual identity, orientation and drive, but the authors make a good case for genetically mediated variation in all these traits. What could be difficult technical material is lucidly presented for a lay audience, which could well include scientists in cognate fields who want a very readable review.

Etcoff's book uses a less rigorous approach. She presents no direct evidence that variation in genes produces differences in behaviour. Instead comparative anthropological studies are quoted, preferably across a wide variety of cultures, to show that the majority of the human race exhibits a particular type of behaviour. If the behaviour can be plausibly explained in Darwinian terms as being adaptive, or more so as probably having been adaptive in the Palaeolithic, this is taken as strong evidence that the behaviour is quite strongly wired into the primitive brain. Sexual behaviour is much the most promising candidate for this treatment: it is reasonable a priori that humans, as much as any other animal, are wired by their genes for successful reproduction; any gene failing to do this should long ago have gone out of evolutionary business.

The hypothesis then is that the perception of human beauty is, at bottom, simply a mediator of sexual attraction. The Graeco-

Roman "ideal" body is not merely a fashion adopted by the Renaissance, but the psychologically preferred form when seeking a mate. The things about female bodies that turn male heads, and that cause high ratings in psychological tests, are strong indicators of female fertility: curves and padding designed to demonstrate a good percentage of adipose tissue (starvation prevents menstruation); glossy hair (an indicator of oestrogen - Etcoff misses this one); youth (plenty of reproductive potential); clear skin (no parasites or disease); puberty (no immediate procreation with the pre-pubescent); and - far from obvious but demonstrated obstetrically to be strongly related to fertility - an hour-glass figure in which the waist-to-hip ratio is less than 80 per cent, and anything down to the 68 per cent displayed by fashion and glamour models. Men appear not to show signs of their actual fertility, and the things which are highly rated by women, such as a good upper torso ("no pecs, no sex") and a good income, are, rather, indicators of the ability to hold a superior social position and therefore to be a good provider. Research with composite images shows that women with an average face tweaked in the direction of immaturity are seen as very beautiful, and career success in men (at least if they want to become generals in the US army) is powerfully dependent on having a dominant face with a square jaw and jutting brows. But with the exception of high symmetry, which is related to fitness, the evolutionary basis for the attractiveness of the ideal female face or the social assertiveness of the ideal male involves a "bootstrap" argument: the faces are effective because they appear quintessential representatives of their gender. Whether or not the explanations are valid, the facts are dynamite. The beautiful are not only more likely to mate, they are also more likely to be helped or even rescued, and are given lighter sentences in law courts. The one advantage that they do not clearly have is increased happiness - a state of mind which is more set, according to Living with Our Genes , by one's innate serotonin balance than by one's circumstances.

The step from human beauty to beautiful mornings and pictures is hard. Infants prefer to gaze at symmetrical patterns, but attempts to find a functional, let alone evolutionary, explanation for the golden section are thoroughly inconclusive. Landscape pictures which are perceived as the most beautiful tend to show tall trees, a good view to the distance, variations of level, water and plentiful exit routes - the features that would make a place safe for living in the Palaeolithic era.

Artists might be expected to show an interest in many aspects of their models beyond simple reproductive pulchritude, as Martin Postle and William Vaughan's The Artist's Model shows is the case with William Etty, whose pictures vindicate his claim never to have painted for erotic interest. Nonetheless, male depictors of the female nude were long suspected of peddling soft porn in public and of improper relations with the models in private. Even Darwin comes in for some dry humour when he is found inquiring of the pre-Raphaelite sculptor Thomas Woolner as to the area of the body over which an inexperienced female model will blush. Etcoff reports blushing as a powerful signal, indicating sexual awareness, and therefore availability, along with the inexperience that is so irresistible to men. Darwin himself, clearly and commendably without direct experience with innocent young ladies, could have asked Etcoff why (as he eventually expounded in The Expression of the Emotions ) men also blush when shamed.

Etcoff's approach is often delightfully stimulating rather than critical. She notes that the Greek painter Zeuxis anticipated the composite photograph (or the modern creation of ideal beauty by using body doubles for film actresses) when he painted a composite image of the five most beautiful women in Crotona. A painting of this event by Edwin Long is described by Postle and Vaughan as "an ideal vehicle for legitimising male fantasy". A poll of the pictures in this book indeed suggests that almost all the female models (whether by selection by the artists, self-selection by the models, or selection by the compilers of the exhibition recently on show at Nottingham University for which this acts as catalogue), have a waist-to-hip ratio of less than 80 per cent, which approaches the male desideratum. The three clear exceptions are interesting: Stanley Spencer's two pictures of Patricia Preece both show her to be running to the Rubenesque, but one poses her in such a way as to generate a temporarily narrow waist. The other two are, significantly, by women, one a tender drawing from the Camden School of a very heavy lady, the other a painting by Gwen John of a young cylindrical model. John found the model painful, obsessed, depressed and complaining of unreturned love, and seems to have expressed her displeasure by a pose and composition that accentuate the boyishness of the figure. QED.

Homosexual artists, exemplified by Henry Scott Tuke, are exonerated of impropriety. Living with Our Genes , Survival of the Prettiest and Robin Baker's Sex in the Future all attempt Darwinian or genetic explanations of homosexuality, but come up with interestingly and strikingly different versions (none considers that the so-called "gay gene" discovered by Hamer himself may simply be a bit of very selfish DNA). Darwinian explanations are suspiciously flexible: what cannot be explained by direct selection on fertility or survival can be explained by the bizarre effects of sexual selection, which are well enough demonstrated in animals. Anything that is not explicable in any of these terms can of course be attributable to culture. It is thus simple for others to dismiss the whole Darwinian exercise as impossible to refute, and therefore vacuous: a reaction both easy and mistaken. The view that the human mind is free of the influence of genes is simply false, not on Etcoff's evidence but on account of the rigorous work recounted by Hamer and Copeland. Given the sound basis of that work in genetics and molecular biochemistry, the exercises in Etcoff, particularly when they can call on animal models, constitute an entirely reasonable set of hypotheses, some less speculative than others. The Telmah theory, with its firm physical base, is an excellent scientific model.

Similarly false is the view that the model constitutes a depressing form of "determinism", or that it arrogantly claims to explain everything about human beings. Hamer and Copeland will have none of this. Having opened each chapter with a sensitively narrated and paradigmatic case history that gives the lie to any idea about biochemistry offering a total explanation of a person, they close it with some suggestions about what to do if you don't much like your neurotransmitters. Although they write favourably of ipramine and Prozac for the modification of "harm avoidance", they liken using drugs generally to curing the leak in the roof by drying out the carpet. They favour personal insight, followed by a determined use of will-power to correct one's character, and give the stirring example of a friend who in this way overcame extremely severe and almost certainly genetically based alcoholism. And if we do not like our appearance, as Etcoff shows, we have long had the option of modifying it. We be-tweeded and apectoral academics may mutter that beauty and fashion "can't matter, won't matter", but the multi-million global turnover in fashion and cosmetics only makes us look blinkered: is it really possible for industry to fool so many people so much of the time? Hamer and Copeland and Etcoff are all firm in the view that obesity is a medical issue.

Baker's book likewise assumes that although many of our social arrangements have the flexibility of fashion, there are elements of human behaviour, bequeathed to us by ages of natural selection, that will change only reluctantly: a drive to reproduce, the enjoyment of sex, an anxiety in women to have resources to raise their children, and in men to raise only a child that is their own genetic issue. He attributes current marriage and mating patterns to the realisation of these biological imperatives, and speculates about our behaviour in the next century, given the huge changes that we are creating in the physiology of reproduction.

With one couple in six in the United States infertile, fertility treatments are hugely profitable and the development of the technologies consequently rapid. So, despite rearguard actions by the churches and the Warnocks, the treatments will soon be available to the fertile, who will first achieve contraception with 100-per-cent certainty by being physically sterilised and, when they decide to have a child, will then use the fertility treatments to bypass the "block". Only Luddites will use the old "organic" method. Ancient sexual urges will be divorced from procreation, leaving sex for companionship, recreation or adventure, no doubt according to one's ranking on the scale of novelty seeking. (This has of course long been on the cards: for all the range of relationships of artists and models in Postle and Vaughan, from the deeply proper to the scandalously passionate or sleazy pre-Raphaelites to the definitely dodgy - Eric Gill's incest and Lewis Carroll's iffy photographs of Alice Liddell, there is only one image of a baby.) Everyone will be able to drop in at what Baker calls the Reproduction Restaurant, choosing from an internet menu of "gamete partners" whom they have never met. The nuclear family will be replaced by something a little, but not much, like the extended family of the past. Reproduction will occur past the menopause, past death even. Paternity testing will be universal, and predatory impecunious women will seduce the few wealthy males who are "unblocked" in order to obtain child-support payments. Unlike the rounded portraits in Hamer and Copeland, the short stories Baker uses to introduce these themes have mostly a nightmarish quality, not so much from their depiction of a population of men with brains in their trousers and women with wallets in their brains, but from their being inhabited by people who when not Rabelaisian are merely intelligent, devious and manipulative (the author having spent most of his life in academia).

When one Ron Harris recently described his auction of the eggs of eight young models at www.ronsangels.com - the ultimate wedding of wealth and beauty - as "Darwin's natural selection at its best" he could have been giving us a reading of Etcoff and Baker. Francis Crick once suggested that the findings of modern psychology would make the novels and dramas of earlier times unreadable. Practitioners of the humanities and of the traditional social sciences should note the warning: reading these books could severely damage your composure.

John Turner is professor of evolutionary genetics, University of Leeds.