Sperm Wars

by Robin Baker

  Lower down in the woman’s tract, in her cervix, many of her partner’s sperm are trying to enter her cervical crypts. But the crypt entrances too are patrolled by killers and, in any case, inside they are virtually full of the lover’s sperm. Just occasionally, some of the partner’s sperm stumble across a channel leading to an empty crypt, but the majority get stranded in the mucus where they fall prey to the combined forces of the lover’s sperm and the woman’s white blood cells.

  Clearly, the Wednesday encounter in this war has gone very much in favour of the lover, and nothing much happens over the next two days to redress the balance. As the woman goes about as normal on Thursday and Friday, the population of blocking sperm from both men in her cervical mucus slowly declines. Some drip into her vagina, carried by mucus. Others are mopped up by rearguard white blood cells. Even when some of these blockers are replaced higher up in her cervix with sperm from the cervical crypts, the new recruits fail to make good the loss and the blockers dwindle. The killer sperm in her womb, after an initial decline from battle losses, actually build up in numbers on Thursday with a fresh recruitment from the cervical crypts. Then the killers also begin to decline in number. A steady flow of egg-getters from both men (but mainly the lover) leave the crypts, heading for the rest areas in the oviducts. En route, they have to run the gauntlet of rival killer sperm in the womb, and most of the partner’s egg-getters fail because these killers are almost all from the lover. By Friday night, with only hours now to go to ovulation, the partner’s egg-getters in the oviducts are outnumbered by about one hundred to one.

  When the woman and her partner have sex on the Friday night, there is only one more hour to ovulation. Now, the partner’s sperm have a much easier passage through the cervical mucus because the number of blockers is much reduced. Although most of his sperm head for the now half-empty cervical crypts, a vanguard of egg-getters and killers head straight for the oviducts. Many are killed or slowed down in the womb by the lover’s patrolling killers, but enough get through to reduce the odds in the oviducts from a hundred to one to about ten to one. It is at this point that the woman produces an egg from one of her ovaries and a chemical signal passes down the adjacent oviduct. This signal activates hundreds of the sperm in the rest area, and a wave of sperm begin to make their way up the oviduct towards the fertilisation zone. It is now a race, or rather an obstacle race, because there are still killers in the oviduct, mainly from the lover. The partner’s sperm, particularly those few which have just arrived straight from the insemination, are actually faster than the lover’s – if all else were equal, the partner could still win the prize of fertilisation.

  But all else is not equal. One after another, the partner’s egg-getters run into the lover’s killer sperm. As the egg reaches the zone of fertilisation in the oviduct and the first sperm arrive, the odds against the partner have reduced to five to one, but that is not enough. The first three sperm to arrive are all from the lover, and one of these claims the prize. An hour later, with the partner’s fresh sperm now overwhelming the lover’s at all points in the woman’s tract, the odds in the oviducts swing heavily in the partner’s favour. But it is too late. The lover has made it and the woman’s daughter, to be born in nine months’ time, will not have been sired by the man she will call her father. But nobody will ever know.

  4

  Counting the Cost

  SCENE 8

  Doesn’t He Look Like His Father?

  As the man drifted back into consciousness, he painfully turned over his left hand which had been resting, palm down, on the bed. His partner reached out and placed her hand in his, distressed by the coolness of his skin. As their eyes met, she shook her head, answering his mute question.

  The man knew that death wasn’t far away, but he couldn’t die yet. He had set himself one last task and had to live just that little bit longer. Despite the drugs and the pain, panic rose within him that he might fail and die too soon. His son was on his way, flying from the other side of the world, and the man desperately wanted to see him just one more time. Nothing else would make his last moments peaceful.

  His eyes closed and he drifted off once again into semi-consciousness. Scenes from the past opened and closed so vividly he could swear he was actually there. He walked into the room where he met his lifelong partner and saw her for the very first time. He saw the blood and water as his son shot that last short distance out into the world. The midwife picked the baby up, identified his boyhood, and in the next breath remarked how much he looked like his father. Then he was wrapped and placed in his father’s arms, his tiny, wizened face pointing upwards, bottom lip quivering as he sucked at a non-existent nipple. It was the most emotional moment of the man’s life, his own flesh and blood there in his arms.

  The man opened his eyes again. Still all he could see was his partner. After their son had been born, she had never really wanted any more children, but he hadn’t minded. Just having the one child meant that they had never needed to stint on their son’s comfort, development and education. At the same time, they had found it relatively easy to become modestly wealthy. Their investment of time and money had been more than repaid by their son’s successes.

  Three times, as his son was growing up, the man was almost tempted into infidelity. But each time, at the last moment, he had resisted for fear it would break up his home. He would have been sad to lose his partner, but he would have been heartbroken to lose his son. The two of them had always been close. They had shared all of those things that a father and son can share, even through the boy’s difficult adolescence. He relived the pride he had felt at seeing him graduate, then watched once more as his career went from strength to strength. He met again the succession of pretty girls who clamoured for his attention, and the beauty who was to become like a daughter to him. He remembered the surges of grand-paternalism as, one by one, they had given him five grandchildren.

  As real as if it were actually happening, he felt himself lift the photograph which was now by his hospital bedside but which for years had had pride of place in his lounge. After his son’s emigration, prompted by a career move apparently too lucrative to refuse, the picture had taken on a special significance. It was of his dynasty, as he called it; a professional photograph of himself, his son and the five grandchildren. As he never tired of saying, the picture showed his contribution to the world and to future generations, a contribution more lasting than any work of art. His son and his grandchildren had already inherited his genes. Now, very soon, they would inherit a large part of his wealth.

  His heart skipped a beat as he thought he saw a young man come into the room. He was sure it was his son, and he looked so well, so successful – and so strangely young. The man smiled. He had done it. He had hung on just long enough.

  His partner knew he was dead. She had felt his hand growing colder and colder. Now he was gone. She thought she had used up all her tears, but more came. After a while, she called for a nurse; then, after a few more moments of contemplation, left the room to wait for her son. He finally arrived two hours later. After she had broken the news to him, the pair of them went in and stood over the man’s body, now totally cold. The woman tried to console her son by telling him that in the man’s last hours, during his few moments of consciousness, he had spoken of nothing else but of him and his family.

  While openly weeping, her son cursed the airport delays and heavy traffic that had made him too late. Then, in an outburst he would later regret, he turned on his mother and swore at her. He cursed her infidelity and lamented the day that she had saddled him with her secret. For ten long years she had made him keep up the pretence until, in the end, the burden had become too much and he had felt driven to emigrate. But most of all, he cursed her for making him hate himself today. During the long flight home, a single thought had plagued his mind. Why am I bothering? – he’s not even my real father.

  On many occasions in this book, we encounter people who enhance their reproductive success
via infidelity. Such behaviour, however, is only advantageous if the person concerned manages to gain the benefits of infidelity without incurring its even greater costs.

  This chapter is concerned with the potential costs of being unfaithful. It consists of Scenes 8 to 11, each of which explores one or more of the costs and dangers of infidelity. Some of these dangers are experienced by the person who is being unfaithful; some by their partner. In this first scene, we examine the reproductive repercussions for a man of being unknowingly tricked into raising another man’s child.

  The comments that people make when they are first confronted by a new-born baby show a surprising preoccupation with seeking a resemblance between the baby and the presumed father. It is not known how often such comments and comparisons are accurate. In Scene 8 the midwife was wrong, but the man would have found it reassuring none the less. But, as life turned out, it might have been better if he hadn’t – he might have been more likely to retrieve his situation, reproductively.

  In his generation’s cruel competition to pass on its genes, the dying man was a reproductive failure. For him there were no descendants; no dynasty. He had been outmanoeuvred in life’s mating game by his partner and a man he never even knew – the man who was the real, genetic, father of his ‘son’. Between them, the two had tricked him into dedicating all of his reproductive effort into raising a child who wasn’t his, just like the small bird that is tricked into raising a monstrous cuckoo chick.

  Had he not been duped in this way, there was in principle nothing wrong with his strategy of having just one child. Recent studies have shown that, all else being equal, increasing one’s wealth and investing more into each child can increase reproductive success just as much as having more children. It does so because each child then has a greater chance of survival, grows to be healthier and wealthier, and so becomes more likely to attract the opposite sex. Eventually, such a child should produce more grandchildren or great-grandchildren than a child who received less investment from his or her parents.

  Sons, in particular, make good investments (Scene 18). Wealthier, healthier sons have more opportunity to inseminate girls before they choose a long-term partner, are more likely to obtain an attractive, fertile and faithful partner, and are more likely to have the opportunity for infidelity. Even apart from the grandchildren such a son might produce through his long-term relationships, he is also more likely to produce ‘satellite’ grandchildren via other women, often in the process tricking other men into raising his children as if they were their own.

  The greatest reproductive success is achieved by people who strike the best balance between the pursuit of wealth and status and the production of children. This principle applies just as much to an African cattle-herder as it does to a Western industrialist. It also applies to other animals. A male bird, for instance, has to strike a balance between gaining a better territory and feeding its young on the one hand, and finding opportunities to mate on the other. The best balance, of course, can be elusive. Spend so long accumulating resources to invest that you never actually find time to reproduce, and your strategy will fail. Spend all your time having children and none accumulating resources, and your strategy again fails. Your children may die of malnutrition or become so unhealthy and disease-ridden that they become unattractive or infertile.

  The single-child strategy, which is the ultimate in investment, can be successful as we have seen – but it can also fail. Moreover, when it does fail, it does so spectacularly. If that child dies through accident or disease or is infertile through some misfortune of genetics or infection, the single-child strategy is a total failure. Or, if your situation is like that of the man in Scene 8, the single-child strategy is again a total failure.

  For the woman in the scene, however, the strategy worked wonderfully. She produced a son who survived and avoided major diseases. Moreover, through his receipt and use of the higher-than-average family wealth, he was able to achieve a status in terms of health and wealth that made him a popular target for attractive and fertile young girls (Scene 18). For all his mother knew, her son might have produced children with some of these other women. He might even have tricked other men in the same way that his genetic father had tricked the man who had just died. Even apart from such potential satellite children, her son had successfully produced five children with his long-term partner. Had the woman had more than the one child, the reduced investment in each could have led to her having fewer grandchildren. As events turned out, her strategy was a good one.

  The strategy also worked well for the genetic father. Not only did he enjoy the same reproductive benefits through his son as did the woman, but he undoubtedly enjoyed further reproductive success with his own long-term partner. Biologically, his success contrasts with the failure of the man who raised his, the genetic father’s, child as if it were his own. Having been deceived early on in his reproductive life, the latter had several opportunities to retrieve the situation but, as events turned out, he responded disadvantageously. He could have been more persuasive in changing his partner’s mind about not having more children, but he wasn’t. He could have taken the opportunities for infidelity that presented themselves, but he didn’t. He could even have left his partner and tried a long-term relationship with another woman who would have given him children, but he didn’t. For him, the dangerous strategy of having only one child was a disaster.

  Had the child he was raising been his own, his character and his responses to the challenge of child-rearing would have been advantageous. The couple would both have reaped the rewards of a successful son. But because the child was not his own, biologically his genetic package of characteristics was a failure. With all the cruelty that is natural selection, his genes were weeded out, never to be passed on to future generations.

  The experience of the dying man in Scene 8 is by no means rare. World wide, it has been calculated from studies of blood groups that about 10 per cent of children are in fact not sired by the man who thinks he is their father. This is also the level found in industrial Western societies (see Scene 18 for further details). There is a real need for an extensive study using modern techniques such as DNA fingerprinting. So far, the nearest thing to such a study comes from the paternity tests carried out by child support agencies. They are responding to absent ‘fathers’ who demand such tests in an attempt to avoid or delay the enforced financial support of an ex-partner. Internationally, child support agencies are reporting a non-paternity rate of about 15 per cent.

  All figures for non-paternity are of the proportion of children actually born. The non-paternity level for children conceived will be even higher. This is because a woman is more likely to abort a child conceived via a man other than her long-term partner. Almost certainly this happens primarily when her partner either knows or has a good chance of finding out that he is not the real father. The abortion then represents an attempt by the woman to avoid the costs of infidelity discussed in Scenes 9 and 11.

  Although properly controlled DNA fingerprinting studies have not been carried out on humans, they have been carried out on a wide range of apparently monogamous birds. The results suggest a roughly 30 per cent incidence of males raising other males’ offspring, comparable with but slightly higher than the level in humans. So it would seem that the average male bird has even less reason to be reassured by a passing resemblance to its offspring than has the average man.

  SCENE 9

  Making Mistakes

  The woman turned the corner, then stopped under a street lamp to check that her keys were in her bag. A few minutes more would see her home, and her spirits were sinking fast. Although the night was cold, she paused for a while under the light – anything to delay the moment of arrival.

  She had spent the evening at her sister’s, about fifteen minutes’ walk away, seeking peace and asking advice. Her sister was in no doubt.

  ‘Take the children and go,’ she had said. ‘Stay with mother – she’ll have you while you sor
t things out.’

  Still standing under the light, the woman fingered her cheek bone. The tenderness had nearly gone, but she knew it wouldn’t be long before the bruises were back again. She took a deep breath, braced herself, and walked the remaining distance to her front gate. She had hoped he would be in bed by now, but as she went up the path she could see that the sitting-room light was still on.

  Her partner didn’t look up when she walked into the room, his gaze staying firmly fixed on the TV screen. There was a can of beer in his hand, and a further eight crushed empty ones littering the floor. She recognised the atmosphere only too well, and knew she had to be careful. For a while she busied herself with minutiae, tidying up the debris of his evening at home with their two children. In the end, she could stand the silence no longer and asked, as calmly as she could manage, if the children had gone to bed without fuss. Without looking at her, he spat his reply. Her children had gone to bed fine. He didn’t have any.

  She knew better than to contradict him. Both of the children were in fact his, but recently he had decided they were not. Since then, he hadn’t missed an opportunity to voice his new-found doubts – to her, to the children, to the neighbours, in fact to anybody who would listen. She sighed more aggressively than she intended, then said that if he was going to start that again, she was going to bed.

  ‘Come here,’ he ordered.

  She hesitated, a familiar fear rising inside her.

  ‘Come here,’ he repeated, even more forcefully, still not looking at her.

  She knew she had no choice. Running away only made him worse. She walked over and stood in front of him. He remained seated.