Sperm Wars

by Robin Baker

  As a sperm approaches the fertilisation zone, it changes its behaviour. Its tail starts to beat more vigorously and, once it arrives, it often swims frantically in circles or figures of eight. At any one time, the fertilisation zone may contain anything from one or two to up to a thousand sperm, all looking for the egg that usually never comes. After a while, they leave the zone, one by one. As each leaves, its place is taken by a new, fresher arrival from the rest area. Having left the fertilisation zone, each sperm then travels the remaining distance up the oviduct until eventually it swims out into the woman’s body cavity – which it can easily manage because the end of her oviduct gapes open, its opening surrounded by finger-like projections.

  Now let’s consider the egg.

  A short distance away from the end of each oviduct, suspended like a relatively huge planet next to a black hole, is an ovary. Tiny hairs on the inside of the oviduct create a current in the body fluid so that when an egg is released by an ovary, it is slowly wafted towards the black hole of the oviduct. Like a waiting hand, the finger-like projections funnel the egg into the tube. From here, the egg begins its five-day journey down towards the womb.

  To achieve fertilisation, a sperm has to do more than simply encounter an egg in the fertilisation zone, because the egg arrives in that zone surrounded by three lines of defence – a fortress that has to be breached by the sperm before the egg will yield. The outer line of defence, the cumulus, is a thick layer of shapeless cells which the egg has brought with it from the ovary. Beneath the cumulus is another relatively thick, smooth layer, the zona, which is the outer membrane of the egg itself. Under the zona is a narrow space which surrounds the final, most vulnerable barrier, the vitelline membrane.

  Using its head, the sperm hacks its way through the cumulus cells. If successful, and it reaches the zona beneath, it sticks the side of its head on to the membrane with chemicals. With this chemical attachment serving as an initial purchase, the sperm again uses its head to cut a way through, this time employing a pointed spike that has been exposed at the tip of its head. The lashing tail provides the force to push the sperm forwards. Finally, if this sperm is the first to get through the zona, cross the underlying space and touch the vitelline membrane, it is engulfed by the egg in a welcoming embrace. Having embraced one sperm, the egg passes a chemical message across its surface and, within seconds, becomes impenetrable. If you are a human sperm, there is no prize for coming second.

  The successful sperm sheds its membranes within the egg, releasing its genetic heart of DNA. This then travels to fuse with the similar heart of the egg. Fusion of the DNA from sperm and egg mixes together the genes from father and mother in equal proportions. A new person has been conceived, with characteristics that are a subtle mixture of his or her two parents.

  We know with certainty the mother of the child in our scene. After all, the child will spend nine months developing inside her. But who is the father? As we saw, in those few critical days before she ovulated the woman had collected sperm from two men – her partner and her lover. To see what happened, and to work out who is the father, we need first to go back ten days. We are about to witness a sperm war.

  3

  Sperm Wars

  SCENE 6

  A Chance Affair

  The woman was out on her Wednesday night ritual with eight of her girlfriends. She had been going out like this for over a year. About a dozen of them were involved, but not everybody went out every week. Typically, their night centred on lots of drinking and talking, a meal and sometimes a club. Occasionally, a man or two would move in and try to prise somebody away from the group. They expected each other from time to time to talk to, and perhaps even leave with, a man. Even though most of them had a male partner at home, the group enjoyed an unspoken sisterly complicity.

  Tonight, it was her turn. Quite by chance, who should walk into the bar but the man she had met during her last schoolgirl summer - the one who, for a few months, had been her weekend sexual partner during her first term as a student. They recognised each other immediately and spent virtually the whole evening talking, catching up on events since their last, rather acrimonious, meeting. She learned that he now worked at the other end of the country but was in town for a week on business, staying in a nearby hotel. Now nearly thirty, he was still not living with anybody, but had a girlfriend – or two.

  He still oozed masculinity, promiscuity – and unreliability. Kudos though there had been in being his girlfriend, she had eventually finished with him on discovering his many and varied infidelities. At that vulnerable stage in her life she had needed someone she could rely on. Now, however, meeting him out of the blue, many of her old feelings returned. All the same, at the end of the evening she rejoined her group.

  At lunchtime the next day, he turned up at her work and took her out for a snatched bar lunch. Over lunch, they arranged to meet for a meal that evening. As it was Thursday and her partner would be out with his friends, she reasoned there was no need or point in telling him. As far as she was concerned, the evening would be totally innocent and therefore not worth mentioning anyway. Even so, she took her ex-boyfriend to a restaurant some way out of town where they were unlikely to be seen.

  All through the evening, it was obvious he was expecting them to end up in bed back at his hotel. He was very attentive and flirtatious and from time to time would find an excuse to touch her. But the thought of infidelity never seriously crossed her mind. She still found him attractive and his touches arousing, but she also found his expectation of sex irritating, almost offensive. As a result, she had long cool phases towards him throughout the evening. Eventually, he got the message and backed off. On the return journey to her home they simply exchanged pleasantries.

  In the few moments before she got out of his car, they spoke as if they were never going to meet again. She surprised herself when a sudden feeling of warmth, nostalgia and maybe guilt prompted her to kiss him briefly on the cheek. She surprised herself even more when she kissed him again, this time on the lips. Somewhat flustered by this momentary surge of passion, she got quickly out of the car, wished him a good life, and went inside.

  When her partner returned home an hour later, she was in bed pretending to be asleep. As he fell into a drunken sleep and began a night of snoring, her thoughts and dreams raced around with the excitement of the evening. At some unknown hour of the night she surfaced just enough to realise she had climaxed in her sleep.

  All the next day, at work, she couldn’t believe how easy it had all been. She had spent the evening, albeit quite innocently, with another man, and absolutely no one had known about it. The man, their evening, their conversation and their kiss, as well as memories of their earlier sex life when she was still a teenager, were at the back of her mind continually as she worked. Her thoughts kept her in an almost permanent state of subliminal excitement. Her knickers were damp virtually all day and on one visit to the toilet she masturbated.

  She didn’t have sex with her partner that Friday night but she did both on Saturday and on Sunday. On Saturday night she more or less insisted that he gave her an orgasm before entering her. It was rare for her to climax during intercourse itself. She never expected to and on the occasions when she really wanted an orgasm she made sure it was during foreplay. On Sunday morning she had masturbated while in the bath, then appeared naked in the lounge and seduced her partner into sex on the floor. During each orgasm over the weekend, even during foreplay, the fantasy in her mind was not of her partner (it never was these days!) but of a real or imaginary scene from the past with her ex-boyfriend.

  All weekend, she secretly relished her burst of sexual activity and excitement. At no point, however, did she ever contemplate doing anything more dangerous than fantasise about illicit sex. But on Monday, back at work, her mood began to change. Her ex-boyfriend was leaving on Thursday and she might never see him again. An idea began to form in her mind and her excitement slowly turned to nervousness. Maybe she should see
him just one more time. It would be easy to arrange. Instead of going out with her friends on Wednesday night, she could spend the evening with him. All she had to do was pick up the phone, call his mobile, and arrange it. Easy.

  The thought both excited and frightened her, so much so that all day Monday she did nothing but relish it. On Tuesday she found the courage to phone just once, but got no answer. After that, her nerve failed and she didn’t try again that day. On Wednesday morning, her mood changed from fear and guilt to one of calm confidence. Why shouldn’t she see him again? He was an old friend and this could be her last opportunity. After all, their previous evening together had been innocent enough – there was no need to feel guilty or nervous. But maybe there was no need to tell anyone, either.

  At her third attempt, he answered his phone. He was pleased and surprised to hear from her but was in a hurry and, without time to discuss arrangements, suggested that she call for him at his hotel that evening. She agreed, and spent the rest of the day in a state of high excitement. She told her friends at work that she had to visit her sister, and so would not be with them at their weekly get-together. She told her partner, as she left him at seven o’clock, that she felt like going on to a club and so might be late. He complained, but not much.

  She was nervous as she arrived at the hotel and the first few minutes of conversation were very awkward. However, even before they had finished their first drink at the hotel bar, it was as if they were students again. The last six years apart had never happened. Tonight, her mood and behaviour were quite different from the previous Thursday. After another drink she sat with her knees touching his, and as the conversation flowed touched him frequently on his leg or arm with her open hand. When he suggested they eat in the hotel restaurant ‘to avoid going out in the cold’, she readily agreed. After eating, he ‘just had to go up to his room’ to get a photograph to show her. She went with him because she had ‘always wanted to see what the rooms were like in this hotel’.

  He never did show her the photograph. Within moments of closing the door they were kissing and removing each other’s clothes. Almost before she could take a breath they were naked on the floor and he was inside her, ejaculating. She had been taken aback by his urgency but made no attempt to slow him down. He did not offer to use a condom or to withdraw, and it never crossed her mind to ask. Her vagina had been wet with anticipation all day and as she walked into his room it had been in full flow. Penetration had been quick and easy and ejaculation had been swift.

  When it was over he apologised, saying that his urgency was because he had never stopped loving her and had been desperate for her. He promised that if they got off the floor and into bed he would make it up to her. And he did. For half an hour he caressed and played with her body with an understanding of her womanhood that her partner had never shown. After she climaxed, they dozed for a while in each other’s arms. Then they began all over again. He still penetrated her early, but this time his urgency had gone. Thrusting was slow and long. Unusually for her, she climaxed during thrusting, just a few seconds before he ejaculated.

  They settled into another post-coital embrace, but their tranquillity did not last for long. For the first time that night, guilt and panic began to grow in her mind. It was getting late. Quickly, her fear became all-consuming. She had to get home. He urged her to stay the night – to phone her partner and give some excuse for not going home. But she would not hear of it. She just had to get home. Eventually, she escaped from his bed on the pretext of going to the toilet. Then she refused to return and began to get dressed. Conversation became tense and forced. She even became irritable with him and their parting was an awkward affair. As she taxied home, her flowback seeped on to her knickers in a replay of past times. But she did not notice. Her mind was too full of what she should do when she got home.

  Quietly, so as not to wake her partner, she undressed, washed herself thoroughly, then got into bed. Then she set about waking and arousing him. When he was erect, even before he was fully awake, she sat astride him, inserted his penis, and after a while managed to get him to ejaculate inside her. He dimly registered that she was very wet but thought no more of it, and concentrated instead on enjoying an intercourse without effort.

  The next day, her ex-boyfriend left for home. They were never to see each other again. The day after that she ovulated and conceived. Over the next three weeks, she and her partner had sex nearly every other day. By the time she discovered her pregnancy, her night of infidelity had become a distant memory. The guilt and fear had all but gone and she could almost believe it had never happened. She gradually convinced herself that the baby was in fact her partner’s. After all, she’d had sex with him about sixteen times that month compared with that single night with her ex-boyfriend.

  Nine months later she was to have a daughter. Two years after that, she and her partner had a son, followed three years later by another daughter. As the elder daughter grew she came to look more and more like her mother. She also became noticeably more attractive, more dynamic and more popular than the two younger children. However, the differences between them seemed no greater than between many brothers and sisters.

  In the years to come, the woman’s partner never once suspected that at the conception of her first child her body had contained sperm from another man, as well as from him. Even she, of course, never knew for certain what happened inside her body over those few critical days. Neither of them was ever to know that the tiny sperm that entered her egg to produce her first daughter was in fact not her partner’s but her ex-boyfriend’s.

  The two scenes (6 and 7) in this short chapter explore first the promotion and then the process of sperm warfare. In fact, only one of these scenes involves people – the one we have just witnessed. Scene 7 is not really a scene at all. As a description of sperm wars in action, it is the only occasion in this book in which it was more appropriate to combine scene with interpretation.

  We have just witnessed a textbook scene of infidelity. The subtleties of behaviour all play their part in influencing the paternity of the woman’s first daughter. We should note in passing the unreliable, promiscuous masculinity of the woman’s ex-boyfriend and that his child showed certain more positive characteristics than the children the woman had with her partner. We should also note the number and timing of her orgasms, both male-induced and via self-stimulation. We will discuss later the significance of these elements. Here, we concentrate on the infidelity itself and on the factors which led the ex-boyfriend’s sperm, rather than the partner’s, to achieve fertilisation. Clearly, the outcome had a major impact on the reproductive success of all three characters in the scene.

  We have already mentioned that a woman is slightly more likely to have routine sex with her partner during the infertile post-ovulatory phase of her cycle (Scene 2). The same is not true for infidelity. A woman is much more likely to have penetrative sex with a man other than her partner during her fertile phase. Moreover, she is much less likely to use or insist on the man using contraception on such occasions.

  In order for these patterns for infidelity to be detected statistically, women must have cycles of mood and behaviour that promote them. We can see a hint of how this might occur, not only in the scene we have just witnessed, but also in the first scene involving this couple. The first month we met them, the woman did not conceive. She was cool towards her partner during her fertile period and we suggested that her lack of conception was a success for her body, not a failure by the couple. At that time, the only man available to her was her partner, and her body had decided – for the conscious brain is not involved here - that it was not yet a good time to give him the paternity of her first child. To achieve this, it had generated a feeling of coolness towards him for the duration of her fertile period.

  This month, a chance meeting with her ex-boyfriend meant that the woman had an alternative potential father for her first child – an alternative which her body actually preferred. She had two oppor
tunities to be unfaithful, first on the Thursday, then on the following Wednesday. She took one opportunity, but not the other. The Thursday evening had been instigated by her ex-boyfriend and the woman was in an infertile phase of her cycle. Her body found barely any attraction in sex with this man. Her coolness that evening had kept him at arm’s length, even though he was manifestly hoping for sex. On the Wednesday, however, her mood was quite different. As she moved into her fertile phase on the Monday, the idea of seeing her ex-boyfriend began to appeal to her. Her motivation to do something about it, however, did not peak until the Wednesday. Unknown to everyone, including herself, this was the day that insemination was most likely to lead to conception.

  When the Wednesday evening came, her mood and body language were very different from the previous Thursday. Most of the leading suggestions still came from the man, but whereas the week before she had made it clear she was not interested, this time she readily cooperated. In his bedroom, she cooperated further to ensure that she obtained his sperm. She accepted penetration and ejaculation with the minimum of foreplay, and ignored the question of contraception completely. Later, her conscious mind would rationalise her behaviour in terms of being overwhelmed by the excitement and passion of the moment. In reality it was simply that, two days in advance of ovulation, her body was eager to collect this man’s sperm. The reason her body wanted a second insemination we shall see later (Scene 25), but once she had collected his sperm she lost interest in staying with him. Then, by far the most important thing was to get back to her partner.

  Subconsciously, there were probably two main reasons why her body engineered such a sudden change of mood towards her lover. In part, the reasoning will also have been in her conscious mind, though she will have given herself slightly different explanations. The underlying strategy her body was pursuing was that, no matter who fathered the child, the man best suited to help her raise it was her partner. It was vital to this strategy, therefore, that any infidelity should not be discovered. Her body generated a fear of discovery and a sense of panic, but needed to recruit her conscious mind to work out the finer details of timing and story-telling. The two together seem to work well. Surveys suggest that one-off infidelities such as this are rarely discovered, and even longer-term infidelities have only a fifty-fifty chance of discovery. On this occasion, as we have seen, the woman succeeded in covering her tracks.