There are two major ways of accounting for this divorce. The first is sociobiology’s answer: modern sexual behaviour is still gene–driven and our use of birth control is (from the genes’ point of view) a mistake, made possible because the genes could not anticipate how we would use our intelligence. The second is memetics’ answer: modern sexual behaviour is meme–driven. Although our basic instincts and desires are still genetically determined, and these desires in turn influence which memes are successful, the memes themselves are now dictating the way we behave.
I am going to explore both these views and consider their strengths and weaknesses. At the risk of gross oversimplification I am going to lump together as ‘sociobiology’ much of the work on sexual behaviour stemming from biology, sociobiology and evolutionary psychology. In spite of some differences, they all agree that the fundamental driving force for sexual behaviour is natural selection acting on genes. They do not consider a second replicator, and in this respect differ clearly from memetics.
Sex and sociobiology
The essence of the sociobiological view is that the genes have set up a system that has worked historically but is not entirely appropriate for today’s situation. The reason is simple enough. Because genes have no foresight, they can never track environmental changes precisely. Natural selection can ensure that organisms are more or less well adapted to the conditions prevailing at the time, and as times change selection pressures change, so that the better adapted organisms survive. This ensures that tracking is quite effective when conditions change slowly – and extinction is always a possibility when tracking fails. But nothing in the evolutionary process can produce precognition. We are in effect, like all other creatures, products of past selection in past environments.
On this sociobiological argument it is not surprising that our behaviour does not always maximise our genetic fitness. Past evolution has given us a brain that is set up to deal with sex, food, and power, and these ideas are prevalent in our society because these factors all contributed to the survival of our genes in the past. We enjoy sex because
animals that enjoyed sex in the past passed on their genes. But evolution has also given us intelligence, which has enabled us to work out the function of sex and manipulate things so as to get the pleasure of sex without the costs of child care. The genes could not have foreseen this and so we have no adaptation against contraception – although, if you agree with E. O. Wilson, you might expect the genes eventually to pull in the leash again and somehow prevent us from reducing our birth rates too far. On this argument our present behaviour is simply a mistake.
Life is full of mistakes. Male frogs quite frequently try to mate with other males and in some species even have to make a ‘release call’ to escape the unwanted – and extremely lengthy – clutch. Homosexuality in many animals, and even in humans, is sometimes interpreted in a similar way, just as a mistake. Birds with elaborate courtship displays can be induced to strut and flutter and sing for stuffed birds or even for just a few appropriately coloured feathers. Male sticklebacks will fight with very simple dummies and even their own reflections. Presumably the mistakes have not been serious enough to warrant the cost of creating more accurate perceptual systems. Courtship rituals have proved a good way to get a mate even if you occasionally end up dancing and singing for a pile of feathers.
Eating inedible things is another common mistake that is not worth the cost of eliminating completely. Most species survive with very crude systems for distinguishing food from non–food. Chicks will peck at anything of roughly the right size on the ground in front of them, and frogs’ tongues will dart out at any small object that moves in the right way. They generally get by perfectly well unless some devious experimenter comes along to trick them. We modern humans have far better visual systems and rarely make such crude mistakes, but we make equally dangerous ones. Selection during our hunter–gatherer past fitted us well for liking sweet and fatty foods. Fish and chips with dollops of sweet tomato ketchup, followed by apple pie with cream and ice–cream would have been extremely good fuel for a
Homo habilis
or an archaic
Homo sapiens.
So we like those tastes, and we enjoy eating chocolates, and doughnuts, and creamy mashed potatoes with sausages and mustard. This is not healthy for an overfed modern
Homo sapiens.
Such mistakes are common in living things.
On this view, birth control and sex for fun, and many other aspects of modern sexual life, are mistakes which the genes have not eliminated -either because the costs would have been too high or simply because the genes, not having foresight, could not eliminate them. However, even if these are mistakes, sociobiologists would argue that most of our sexual
behaviour is not. It is the kind of behaviour that served, in the past, to get our genes into the next generation, and will go on doing so in the future.
We should not underestimate how successful sociobiology has been in addressing this central topic, nor how hard a fight it initially had for acceptance. For many decades the popular view was that human beings were somehow above nature and not subject to the constraints of genes and biology. In sexual behaviour, it was thought, we alone could transcend ‘mere’ biology and make rational conscious choices about whom we made love to and how. Even though nothing is closer to the propagation of genes than sexual behaviour, the theories of the 1950s and 1960s completely ignored biological facts. They made culture the overriding force but, unlike memetics, had no Darwinian account of how culture could exert such a force. With the advent of sociobiology in the 1970s we could begin to make sense of some of our peculiar sexual proclivities (see e.g. Matt Ridley 1993; Symons 1979).
Love, beauty, and parental investment
Consider mate choice. We may like to think that we chose our lover for reasons that have nothing to do with genes and biology; maybe we just fell in love, maybe we chose rationally because he fitted our notion of a perfect husband, or maybe we chose for aesthetic reasons because – well, because he’s gorgeous. The truth appears to be that romance and falling in love are themselves based on our deep–seated tendencies to pick sexual partners in ways that would, in our far past, have enhanced the chances of passing our genes into the next generation.
For a start, just how attractive is your partner? I could make a guess that he or she will be just about as attractive as you are. Why? The logic of what is called ‘assortative mating’ is very simple. Whether you are male or female you need to get the best mate you possibly can. Inasmuch as beauty is relevant to what is ‘best’ you will go for the most beautiful partner you can get. But then so will everyone else. The result should be, on the average, that people pair up with partners that more or less match them in attractiveness, and this is just what has been found in experiments.
But what is beauty? What makes a man or a woman attractive? The simple answer seems to be that men find women attractive when they have all the signs of being young and fertile, while women are more interested in the status of a potential lover than in his physical appearance. This turns out to have a good biological basis – if a rather complex one.
The basic difference between being male and being female is that
females produce the eggs and males the sperm – indeed this is the usual definition of the sexes in widely diverse species. Eggs are large and contain food for the growing embryo, so they are expensive to make, while sperm are tiny and relatively cheap. Eggs are therefore made in smaller quantities and need to be guarded, while sperm can more readily be squandered. In addition, many females also provide a great deal of parental care beyond the provision of an egg, and it is parental care that really makes the difference when it comes to choosing a mate.
The logic of parental investment was initially worked out by the biologist Robert Trivers (1972), following Fisher (1930) who called it ‘parental expenditure’. Trivers showed how the sexual behaviour of many different species could be explained by considering how much resources each sex puts into bringing up the offspring. This new understanding was then applied to human behaviour by early sociobiologists. Humans are an interesting case, complicated by the fact that our babies require intensive care for many years and are still unable to fend entirely for themselves for years after weaning. Male parental investment is high compared with other mammals, with males providing food and protection for the family. However, male investment is still much lower than female investment in both traditional and industrialised societies. In existing hunter–gatherer societies women have been shown to provide far more of the nutritionally valuable food for their children than men do and to spend many more hours per day working. Even in our supposedly emancipated Western societies some estimates suggest that women work on average twice as many hours per day as men – that is, including paid jobs, housework, and child care. This disparity in parental investment can explain a lot about human sex.
A human female can produce a maximum of roughly one baby a year in her fertile years, amounting to perhaps twenty or twenty–five in a lifetime. The highest ever recorded is supposedly sixty–nine babies, mostly triplets, born to a nineteenth–century Moscow woman. However, human babies require enormous amounts of care, and in traditional hunter–gatherer societies women probably produced one about every three or four years, spacing the children, as hunter–gatherers do today, by sexual abstinence, long lactation and sometimes infanticide. The simple fact is that a woman cannot increase the number of children she can successfully raise by mating more frequently or with more men.
By contrast a man can, potentially, produce a huge number of offspring. The more women he can impregnate the more babies he will have, and he can more or less rely on the mother to give them some care. Even if some do not survive he will only have invested a few sperm and a
brief (and probably pleasurable) effort in producing them. From this simple unfairness follows a world of sexual difference.
For men, the most obvious strategy for passing on the most genes is simply to mate as often as you can with whomever you can. A common and effective method is to have one long–term partner whom you protect as well as you can from other men and whose children you care for, while trying to impregnate as many other women as you can, ideally without getting caught.
Women will pass on the most genes if they can raise a few high–quality children with sufficient resources and care to bring them up. This might mean: (a) mating with a high quality male (i.e. one with good genes), and (b) finding a male who will provide a lot of parental care. These may not always be the same man.
One consequence of this disparity is that females need to be far more choosy about whom they mate with. They do not want to get lumbered with being pregnant by a lazy, ugly, feeble or unhealthy man who will provide poor genes and no care and support for them or their infants. This could explain why women proverbially hold back from sex, and more often have to be persuaded or bought presents. Men do not need to be so choosy. If they can impregnate almost any female it will be worth the small effort because they will not be left holding the baby. This can explain why men are normally much more keen to find sex than women are, and a woman who wants sex can usually find it without too much trouble – and indeed can get paid for it.
Many people seem to hate the idea that their own sexuality comes down to such a crude calculation, but the evidence is piling up against the early anthropologists’ idea that sexual behaviour is completely different in each culture. More thorough research now shows that men and women conform to what one would expect based on the principle of higher female parental investment. Men are keener to have sex and are especially turned on by the idea (or the actuality) of sex with many different partners, while women are more choosy and prefer one reliable partner. Prostitution throughout the centuries has been almost exclusively a service rendered by females and paid for by males.
But what about female beauty? Although a man may not lose much by mating with almost any woman, his genes will fare best if he can impregnate a young, healthy and fertile woman. Evolutionary psychologist David Buss found that in every one of thirty–seven cultures, males preferred younger mates and females preferred older ones (Buss 1994). This desire for youth and fertility may explain one of sociobiology’s oft–derided findings that men prefer women with a low waist–to-hip ratio
(Singh 1993). Cultures vary in the preferred fatness or thinness of women – with our present obsession for thinness being rather exceptional – but there is apparently a consistent preference for women with narrow waists and broad hips. The reasons for this are still disputed but broad hips appear to suggest a wide birth canal for safely delivering a big–headed baby (of course they may only suggest it and the fat be a deception). A small waist suggests that the woman is not already pregnant, and the last thing a male should want is sex with a pregnant female who may trap him into caring for another man’s baby.
Large, clear eyes, smooth skin, fair hair, and symmetrical features are good indicators of youth and health – fairness because in fair–skinned peoples hair colour darkens with age, and symmetry because the effects of disease are often to create asymmetrical blemishes. A long genetic history has created men who respond with sexual arousal to the signs of a young and fertile woman (Matt Ridley 1993).
Meanwhile, the woman need be less concerned with beauty and physical appearance. Her need is for a high–status male who will prove to be a good protector and provider. This fits with the frequent (if depressing) observation that rich and powerful men pair up with young beautiful women. It also fits with the results of surveys showing that men consistently rate physical appearance as important in a partner while women are more impressed by signs of wealth and status. Indeed, looks are critical in women but not men. In all the cultures studied by Buss, the men placed more value on a woman’s looks and women placed more value on a man’s financial prospects.