Parousia,
the book is called Human Instinct by Professor Lord Robert Winston, due to be published next month.
Here is the extract I read:
Secret of sex appeal
ROBERT WINSTON
17nov02
THE majority of people have no problem with the idea that humans are descended from apes. But while we accept that our general shape and structure is derived from other creatures, we rarely consider the psychological implications.
Up to 10 million years after the appearance on Earth of our earliest ancestors, homo sapiens not only looks, moves and breathes like an ape: he also thinks like one. Many of our instinctive reactions and emotions are unnecessary in the modern age, but they continue to shape the way we live.
Of all the human instincts, sex shouts the loudest: we are obsessed. Even when our behaviour is not overtly sexual, we spend a great deal of time in activities that are, in a fundamental way, connected with sex or reproduction: money, career, appearance, friendships, competition.
Sex begins with looking for a mate. Most homo sapiens have a complex series of tests that potential mates must pass if they are to prove suitable. Men from different cultures are attracted to varying types of female body, but there is one universal attraction: men throughout the world choose mates whose hip measurements are much bigger than their waistlines.
The preferred waist-to-hip ratio is 0.7 to one. This ratio is as true for Kate Moss as for Sophia Loren; was as true for Audrey Hepburn as for Marilyn Monroe. It even holds for ancient "Venus" figurines, the small stone sculptures of women found across Europe and Asia, which were possibly connected to fertility cults: although many of these figurines are enormously fat, all of them adhere to the "golden" ratio.
Possibly, the waist-to-hip ratio tells a man about a woman's health and, by extension, her fertility. After puberty, oestrogen causes increasing amounts of fat to be laid down on a woman's thighs, buttocks and breasts and this fat was once likely to be important for the survival of both mother and child.
Males are also attracted to symmetrical faces and unconsciously register even tiny asymmetries. We are all born with a highly developed ability to recognise different faces: men apparently redirect this talent later in life towards selecting desirable mates.
A remarkably precise formula for the perfect female face was drawn up by Pythagoras. For someone to be "beautiful", he argued, the ratio of the width of the mouth to the width of the nose should be 1.618 to one. This ratio should also hold for the width of the cheekbones in relation to the width of the mouth. The face of your favourite supermodel would probably fit Pythagoras's formula.
Some years ago, a group of researchers in New York began to investigate the genetics of mating. They started by looking at laboratory mice, concentrating on a group of genes called the MHC genes, which are present in nearly all the cells of mammals and play a major role in the immune system.
Remarkably, the researchers found that mice were much more likely to mate with partners who had dissimilar MHCs.
It turns out that there could be something very useful about choosing a mate with a different MHC. We all carry genetic defects in our DNA, which could be fatal to our children; but if we mate with someone who does not have the identical defect, our children will nearly always be protected.
So how do we detect if a potential mate has similar MHC genes to our own? One answer is provided by studies involving T-shirt-sniffing. Researchers at the University of Berne in Switzerland tested the MHC genes of a number of female students and arranged them into types.
They then asked a group of male students, whose MHC genes were also typed, to wear cotton T-shirts so that their body odour permeated the fabric. The T-shirts were taken to a laboratory, where they were sniffed by each of the women. The women rated them according to how "pleasant" they found the smell.
And indeed, the female volunteers consistently preferred the smell of T-shirts that had been worn by men with dissimilar MHC genes to their own. The results suggest we can literally sniff out a suitable mate.
When two people do finally sniff each other out and fall in love, there is a period of time on average lasting for about 18 months to three years during which passion is at its height. This state of mind has a lot to do with the so-called "love drug" called phenylethylamine, or PEA. This chemical is produced in the brain in large quantities during this fiery period of ardour and amour, and its effects are somewhat similar to amphetamines, or "speed".
PEA is present not only in the brain nuclei of love-struck couples; it accompanies other intense experiences, too. Parachute jumpers' PEA production goes into overdrive during a free fall.
What is clear is that either we fall in love to get our PEA injection, like an addict finding his next fix, or the PEA is our "reward" for falling in love. That chemical aspect of infatuation must have evolved over thousands of years to bond us to the person in question. But whichever comes first, PEA or love itself, the trip, like all good things, must come to an end. Love is, literally, a drug, and a highly addictive one at that. And, like all addictions, there is a law of diminishing returns. The positive effects wear off after a certain period of time. After the initial intense period, your brain starts to pump out endorphins brain opiates that are more like morphine than speed, serving to calm the mind, kill pain and reduce anxiety.
Why do we appear to be pre-programmed eventually to lose interest in a sexual partner? The evolutionary psychologist Helen Fisher suggests that humans pursue a similar strategy to animals such as foxes. Foxes are serially monogamous: they pair up for just one breeding season and stay together long enough to help raise their young before splitting up. Fisher argues that humans, too, are designed to be monogamous only for the time it takes to raise a single child through infancy about four years.
In the UK, between 40 and 50 per cent of marriages end in divorce.
After conducting research in nearly 60 countries, Fisher has backed up her claims by showing that divorce rates peak about four years into marriage.
According to this theory, every marriage is a divorce waiting to happen. Some understanding of the reasons for this may be found by studying the habits of contemporary hunter-gatherer societies the closest modern-day comparisons to ancient human life on the savannah.
In traditional societies such as the Australian Aborigines and the Nersilik Eskimos, there is a much longer period of breast-feeding than in the West until the child is about three or four years old. After this four-year period, the mother gives birth to another child.
The whole point of monogamy is, to be harshly utilitarian, that a partnership provides protection and resources for its own biological children. There's one huge stumbling block for men, though. How do they ever know for certain that the children are their own? Homo sapiens is an unusual species in that the female's monthly period of fertility is hidden unlike species such as baboons or bonobos, who are not shy about broadcasting their fertile condition to the entire troop: during their period of "oestrus", their entire genital area swells and turns a bright pink.
Human females do no such thing. They themselves often tend to be unaware when they are ovulating. Concealed ovulation is a clever ruse. It goes hand in hand with internal fertilisation.
Just possibly, both concealed ovulation and internal fertilisation evolved as mechanisms to ensure that a woman's mate was attentive all month long. They reduce the risk of desertion by the male, which itself reduces the risk of the male forging relationships with other women.
Were these, perhaps, the very beginnings of a trend towards monogamy in human culture?
I once came across an extraordinary clinical situation at my infertility clinic at Hammersmith Hospital, London. Margaret B. came for investigation of her infertility in her early 30s. Exhaustive tests failed to find the slightest thing wrong. I could even find sperm in her uterus on examination many hours after intercourse. Her husband, too, seemed in good health, with an apparently excellent sperm count.
One day, some years after she had first come to me, I said that perhaps the problem could be with her husband. She looked at me for a long time, started crying and said: "No, it must be me."
Eventually, her story poured out. She had been sleeping regularly with her husband, but for the past six years she had been having regular intercourse, sometimes on the same day and even when she was being treated by me, with her longstanding lover. "And he has three children, so I know he's fertile," she told me. Three months later, Margaret came to my clinic to tell me that she and her lover had taken a momentous decision. She had just seen him off at London airport he had decided to emigrate. Only five weeks after her final farewell at the airport, she phoned to say that she had just missed her period and the pregnancy test was positive. And this time there was only one possible father.
At the University of Manchester, Robin Baker and Mark Bellis have argued that human spermatozoa come in different shapes and sizes precisely because they may face a battle against a competing male's. According to their studies, the most common sperm are the standard-issue "egg-getter", with conical heads and long tails, designed to swim for their lives.
But a different type of sperm is also ejaculated: these have coiled tails, so swimming certainly isn't their forte; instead they act as kamikaze sperm, wrapping themselves around the foreign egg-getters and hampering their progress.
These researchers are convinced that sperm competition has been the main force to shape the genetic program that drives human sexuality. I believe their views are fanciful most of the unusual-looking sperm in human ejaculates are simply abnormal.
But whatever the truth of all this, it is possible that adultery is an evolutionary adaptation that has grown up alongside monogamy and long-term commitment.
Some estimates suggest that about 50 per cent of British married men and women are having extra-marital affairs.
We already know some of the genetic reasons why men want to have affairs. They're programmed to spread their genes. If a man has a chance of impregnating another female especially one who is already married and would not have to be provided for then he may well have stumbled across the ultimate evolutionary bargain: all the benefits of continuing his genetic legacy, with none of the work involved in bringing up a child.
What, for a woman, is the evolutionary advantage of taking on a lover? We now know that women in all societies regularly have affairs. Indeed, genetic studies in rural parts of the UK suggest that up to 15 per cent of children are not the offspring of their "official" father.
One way of explaining female infidelity is that it's a woman's way of hedging her bets. The security of knowing there is more than one "provider" for you and your children cannot be taken lightly.
Adultery, for a woman, is also about dipping into the genetic pool. Your current husband may be infertile, or may simply carry poor genes. Taking a lover is one way to introduce different DNA into the litter without destroying the stability of the family structure.
A man's libido has a darker side, too. Sociologists have traditionally viewed rape as a pathological form of behaviour, a crime committed by dysfunctional individuals. It is difficult to conceive of rape being described as "useful" from the point of view of human evolution, yet that, controversially, is what some researchers have recently suggested.
While making it very clear that their theory does not provide any moral justification for rape, they argue that, historically, it is possible that it could have been in a man's interest to force a woman to have sex.
There are some studies that bizarrely indicate that, for some unknown reason, the chances of a woman conceiving from a single act of rape are more than twice those of a woman who engages in a single act of consensual sex.
Some scientists have suggested that rape increases secretion of stress hormones in the body and that these may, if the rape takes place somewhere near the middle of the menstrual cycle, trigger ovulation. Is this some throwback to the time of the caveman? Certainly, if true, this statistic provides a possible evolutionary reason for rape and suggests that certain feminists might not have been so wrong when they said every man is a (potential) rapist.
My own research has come up with some very different results. I wondered whether sex that the female partner found pleasurable improved the chances of her having a successful conception. We asked several hundred infertile women about their regular sexual experiences.
Two hundred women with a known cause for infertility (about half of them had blocked fallopian tubes) were compared with a group of 200 women who had no known cause for being infertile. In all cases, their partners had sperm counts within the normal fertile range.
We found that women who were infertile with no apparent cause reached orgasm less regularly or reported experiencing less pleasurable sex. The control group, with a clear cause for infertility, generally reported more sexual satisfaction. One possible explanation for this is that female orgasm assists the transport of sperm through the uterus and into the fallopian tubes.
If sex that is pleasurable to the woman does improve the chances of conception, it must be in the man's interest to ensure that his partner reaches orgasm. This may explain why most men seem to enjoy sex more when their partners do, too.
Men of all cultures tend to find younger women more sexually attractive. A woman who is young and healthy has a better chance of bearing a number of children, who in turn will be successful and go on to reproduce. For some men, the loss of sexual interest often found in a long-term monogamous relationship, combined with the ageing of their partner, prompts a "mid-life crisis".
A small minority of men who are sufficiently attractive, or who have high-status jobs, end up marrying a younger woman; in some cases, a succession of younger women. Men who marry these women are catching them in their fertile prime; on an unconscious, biological level they may be striving to maximise their genetic legacy.
In fact, they are practising a kind of polygamy: even though they don't keep more than one wife at a time, they're marrying women in their prime and then discarding them, so the principle holds.
Polygamy, monogamy, marriage, children all these relationships are inextricably bound up in our genetic heritage. Shadows of the savannah will always be present, cast over modern mores and ways of life. Slowly, we are starting to grasp the very basic truths about human relationships, and not all of them are easy to accept.
Human Instinct to be published by Random House next month for $59.95
