Sperm wars pdf free download

Published on Aug 25,. Sperm wars. Filter by page count. Your email address will not be published. Home for book free pdf your movie about what the how love quotes with you life and read. Sperm Wars: Infidelity, Sexual Conflict, and Other Bedroom Battles by Robin Baker Published to acclaim and controversy a decade ago, Sperm Wars is a revolutionary thesis about sex that turned centuries-old biological assumptions on their head. Evolution has programmed men to conquer and monopolize women while women, without ever knowing they are doing it, seek the best genetic input on offer from potential sexual partners.

In this book, best-selling author Robin Baker reveals these new facts of life: ten percent of children are not fathered by their fathers; less than one percent of a mans sperm is capable of fertilizing anything the rest is there to fight off all other mens sperm ; smart vaginal mucus encourages some sperm but blocks others; and a woman is far more likely to conceive through a casual fling than through sex with her regular partner.

Its no wonder that Sperm Wars is a classic of popular science writing that will surprise, entertain, and even shock. Tatiana's Sex Sperm Wars made me realize how evolutionary biology got such a bad rap. All's fair in love and war particularly when love is war.

Sperm competition has long been a hot topic in evolutionary biology, Baker, R. Home Contact. Book Details:. Within days of meeting they of her partner fertilising her egg. Another way is to get rid of had sex and thereafter did so whenever the opportunity some or all of his sperm. Most people will never have looked at presented itself. At first they had used condoms, but eventually the damp patch on their sheet after sex and marvelled at she had agreed to go on the pill.

When summer was over and women's power and sophistication. My hope, however, is that they had each gone to their separate colleges, they had, for a after reading the next scene, that damp patch will never seem few months, continued their relationship, taking it in turns at the same again. On such weekends, they always spent the Sunday afternoon in bed having sex. Invariably, they would stay in bed until the very last moment. Then there would be a mad scramble to dress and get to the station in time to catch the last train.

Whenever she was returning from visiting him she could guarantee that no sooner would she have just settled comfortably in her seat than she would begin to feel the fruits of their intercourse seeping out on to her knickers. She would then spend the rest of the journey with a clammy sensation between her legs.

In zebra, within minutes of wakefulness. With great effort she got out of bed, made her way insemination, the mare promptly ejects a major part of the unsteadily to the toilet, switched on the light, sat down and, stallion's ejaculate. Women are not as blatant as female zebra, urinated. As she stood up to flush the cistern she looked down and it might seem that a dribble down the leg can hardly into the bowl.

There, in the water, were four white, almost compare with the zebra's vigorous response. But as part of my spherical globules. It crossed her sleepy mind as she went back research I have had to take a closer interest in flowbacks than to bed that maybe she hadn't yet conceived because she had a perhaps most people, and I can report that women need not, problem retaining sperm. However, no sooner had the thought] actually, feel at all inferior in this respect.

Tonight, at least, the sheet had remained dry. If you are female, try using a mirror to watch the flowback emerge when you urinate about thirty to forty-five minutes after intercourse. You can't do this on a here are probably few aspects of sex as misunderstood T and maligned as the 'flowback', that collection of material that flows back out of the vagina sometime after toilet, so instead try urinating into an empty bath.

Crouch down. Separate your pubic hairs and vulval lips so that the urine will squirt forward. Choose your moment. Wait until you can feel intercourse. To most people it is an irritation and to some even a that the flowback is gathering, then urinate.

Viewing it from the worry, a threat to their fertility. The main urethra while, a centimetre or so lower down, when the correct part is the seminal fluid introduced by the man, almost all of muscles contract, the flowback is squirted out of the vagina which is ejected from the vagina. To this the woman adds a with impressive force. If you are male, see if you can persuade quantity of mucus from her cervix.

There are also cells from the your partner to let you watch her eject the flowback. Whether inside of the vagina, dislodged by the thrusting of the penis.

But you are male or female, you will be left in very little doubt that the most common cells in the flowback are the sperm — and the flowback is the female's ejection of part of the inseminate there are usually millions of them. From the human perspective, that she has just received from the male. At first sight it might seem an to do this.

Monkeys, rabbits, mice, sparrows — and probably all impossible transformation of image to convert a damp patch] on other female mammals and birds — also eject a flowback. Yet that is just what I want to try to do.

I want to argue How do females do it? Before I can explain what happens in that the flowback is one of a woman's major weapons in her humans, I need to do two things. First, I need to describe in pursuit of reproductive success.

Secondly, I need to describe what happens to the ejaculate in One of my favourite photographs of recent years is of a that critical first half-hour or so after insemination. These family of zebra: a stallion, a mare and a young foal. The stallion descriptions will take some time. The foal is looking the other way, seemingly embarrassed to watch, as its mother ejects from give the woman on the bed in front of you an internal her examination.

She is lying on her back. The chamber just inside is starring role in this book. To understand much of human the vestibule. If your eyesight is good and you separate the sexuality, we need to appreciate the beauty of a woman's vulval lips well enough you will see, opening into the top of mucus and the amazing things she does with it. She has the vestibule, the urethra through which she urinates.

On the one hand, Next, you slip two fingers between the vulval lips into her it is her last defence against the bacteria and other disease vagina and gently push them as far as they will go. First, note organisms which are forever trying to invade her cervix and that the vagina is in contact with your fingers all the way womb. On the other hand, she needs it to allow passage to round.

This is because, when there is nothing inside it, the sperm on their way in and to her menstrual flow on its way out. And not only is the vagina not a tunnel, it is not even Most people think of mucus rather contemptuously as a messy, a throughway. The popular image of it as a tube leading amorphous substance, probably because their main contact is straight into the womb through the cervix is quite wrong. It is with the mucus that comes out of their noses. Cervical mucus also quite wrong to imagine that dead-eye dicks can actually may look and feel like nose mucus, but it is in fact very shoot their ejaculate, through the cervix straight into the womb.

It is wonderful stuff with an immaculate structure Both of these images are false because the vagina is, in fact, a and is absolutely vital to a woman's health, safety — and dead-end. Of course, there is an exit into the womb, but it is not sexual power. It contains fibres and is permeated by channels. The womb, from the vagina to the inner regions of the cervix and beyond.

The narrow end of in the top half of the cervix, furthest from the vagina. After the pear is the cervix and it is the cervix that penetrates the roof being secreted, it slowly flows in glacier-like fashion down of the vagina, projecting through by a couple of centimetres.

If through the cervix, eventually dripping into the vagina. The rate your fingers are long enough — many aren't — their tips can of flow of this cervical glacier is slow compared with the speed feel the cervix sticking through the vaginal roof. The cervix has of a swimming sperm but fast compared with the speed of a narrow channel running though it, and it is this channel which invading disease organisms. Bacterial and other invaders are connects the vagina to the inside of the womb and through carried out of the cervix back into the vagina before they can which the sperm must pass on their way in.

It is also through take hold. In the vagina, they are killed by the acidity of the this channel that, in a phenomenal feat of engineering and vaginal juices. During menstruation, the menstrual flow simply elasticity, a baby must pass on its way out. For the moment, adds to the mucus flow. The double flow makes it even more though, let's concentrate on the narrowness of the channel and difficult for disease organisms to invade — especially important on sperm going in.

It is filled with it particularly vulnerable. But particularly great because of their strategy of copulating where since the advantage of retaining sperm during sub-fertile they would seem to have little use for sperm. We have already phases is relatively small, a woman can afford to make her discussed why women have sex at infertile stages of their cervical filter more hostile to sperm in order to increase her menstrual cycle Scene 2 — to confuse men.

Post-menopausal defence against infection. At the approach of ovulation, the women also copulate to confuse men, often continuing to be sexually active for many years after their last period.

By advantage of allowing more sperm through her cervix naturally preventing a partner from identifying the end of her increases, so she makes things as easy as possible for sperm at reproductive life with certainty, a post-menopausal woman is this time. The way she facilitates or impedes sperm passage able to reduce the chances of being deserted for a younger, during fertile and sub-fertile phases is by altering the nature of more fertile woman.

In fact, women who are apparently post- the cervical mucus. The narrow Even pregnant women continue to copulate — again to mucus channels are small in number, and although sperm can confuse men, but for particular reasons that we shall discus in connection with Scene Even those that can At all times, a woman has to balance the advantages of penetrate do so more slowly. During this phase the flow of letting sperm through and keeping disease organisms out mucus is slow, but fast enough to do its job of combating Clearly, making life easier for sperm makes it easier for disease disease.

In contrast, during her short fertile phases, the mucus organisms too. During pregnancy, a woman has no us for the changes: it becomes much more liquid and stretchy and the sperm she collects during copulation, and she ejects the whole channels become bigger. It is more easily invaded by both inseminate in her flowback; her cervical filter makes life sperm and bacteria. At all times other than during pregnancy, however, ; Woman's fertile phases is that not all channels are clear of the sexually active woman may have some use for sperm, and she blockages referred to earlier.

To remove these, and to combat then needs to sacrifice some of her defence against disease in the increased risk of infection, the woman increases the flow order to allow sperm through.

And just as the advantage of rate of her mucus. This way she flushes out cells, bacteria and allowing sperm passage varies over the span of her life and other debris. She is aware of being wet more of the time and a during her menstrual cycle, so too does the strength of her clear, sweet-smelling secretion appears on her underwear. Although the benefit of these changes in the cervical mucus A non-pregnant woman has least use for sperm during the is clear, they could create a problem.

They could threaten a sub-fertile phases of her life such as during most of each woman's attempts to hide her fertile phase from both her menstrual cycle and after the menopause. Even during these partner and herself Scene 2. Her body overcomes this threat phases, though, she gains some benefit from allowing sperm by making the increase in mucus secretion more erratic and passage, because sperm allowed through during a sub-fertile more spread out than would be necessary just to aid the phase can influence the sperm present at the beginning of passage of sperm through her cervix.

Consequently, although cervical mucus help me in my description, suppose that you have volunteered to gives some clue as to the timing of a woman's fertile phase, it is take part in such an experiment.

You are having intercourse in the too unpredictable to ruin her overall strategy. You can see And no matter what the phase of her menstrual cycle, a woman what is being filmed on a big TV screen on the wall in front of can enhance the mucus's filtering efficiency by blocking the you. The more channels she blocks, the stronger the filter.

So As the penis pushes forward into the vagina for the first time, what does she use to block her mucus channels?

There are three the vagina walls part and, when the penis is fully in, you can see things. One is the blood, tissue and other debris from the blind end of the vagina some distance ahead.

Still slightly menstruation. Another is white blood cells Scene 4. And the ahead, sticking through the vagina's roof, is the cervix. At the third is sperm Scene 7.

These blocks may last for several days moment, with its central, dimple-like opening, it looks like a pink but are eventually lost when they are carried inexorably by the sea anemone shorn of its tentacles. But it will change as cervical glacier of mucus into the vagina. Later, we shall see that intercourse proceeds. Scenes 22 to Each time the penis pushes forward, the walls part. Whenever the Even once it is in the vagina, the mucus's job is not finished.

It penis is fully inserted, you can see the end wall of the vagina and flows down the walls of the vagina, coating them with a thin film. As thrusting continues, the picture at full Some exits, contributing to the 'wetness' a woman feels on her insertion changes. The far end of the vagina becomes more like a vaginal lips.

Much of the mucus film, however, remains on her chamber, slowly filling with air and becoming slippery with vaginal walls — representing advance preparation for her next mucus. Even more dramatically, the cervix begins to stretch and intercourse, even if it does not happen for days. When she hang down more and more. Gradually it looks less and less like a eventually becomes aroused during foreplay, her vaginal walls sea anemone and more and more like a pink, rather broad, begin to 'sweat'.

The sweat itself is not slippery. But when it elephant's trunk. Eventually, all you see in front of the fully mixes with the film of old cervical mucus, the result is a very inserted penis is the front wall of the cervical trunk. Its opening effective lubricant. The vagina is now ready for penetration and points down to the vaginal floor and cannot really be seen.

Towards the climax of intercourse, the cervical opening may even We now have all the information necessary to follow the rest on the vaginal floor.

When the penis ejaculates, the spurts of events that take place from first penetration of the vagina by a semen hit the front wall of the cervix and run down on to the floor penis to the production of the flowback.

But to help us along, we of the vagina, forming a pool at the bottom of the chamber. What I am about to like an elephant's trunk at a watering hole, is the cervix.

As it does so, the vaginal walls close behind sex. With the ripples begin to massage the mixture of old semen, mucus, sperm shrinking of the penis, we lose our camera-bearer and our TV and other cells down the vagina.

Eventually, the mixture collects screen goes dark. However, by now it doesn't matter much — in the vestibule. On average, this happens about half an hour after although critical events are taking place, these are chemical and ejaculation, but can occur as soon as ten minutes or as long as two microscopic rather than obvious.

Before this, a woman can stand up, walk around, even The first thing that happens — and we might almost have seen urinate, and she will not eject the flowback. Once the flowback this on our TV screen just before the penis shrank too far down the has collected in the vestibule, however, any one of these activities, vagina — is that the seminal pool coagulates, becoming slightly or even a cough or sneeze, will rid her of the unwanted material.

The second thing that Even if she stays asleep, the flowback becomes so liquid after happens is that sperm start to migrate out of the seminal pool. Imagine that the cervix really is an have been introduced — sometimes more, sometimes less. How elephant's trunk, dipping into a large pool of semen.

The trunk is many depends in part on the severity of the woman's cervical full of mucus. This mucus, however, does not dissolve in or even filter. Quite often about one in ten occasions the filler is so mix with the semen when the two come into contact. Instead, severe that she ejects almost all of the inseminate; more rarely, her something much more structured takes place.

Most important of all, The interface between mucus and semen at the mouth of the the proportion of sperm that she keeps It not due to simple chance.

They penetrate a just her cervical filter. Each time she has sex, a woman's body short distance into the cervical trunk, stretching upwards into the decides how many sperm to keep and how many to eject. How mucus like the fingers of a rubber glove. Sperm frantically swim and why, we shall see later. It won't be long before this female into these fingers, and from there stream into the narrower ability becomes very important in the lives of our couple.

But not channels of the mucus, leaving the seminal fluid behind. Later we just yet. After a few minutes dipped into the seminal pool, the cervical trunk begins to shrink back to the roof of the vagina, metamorphosing once more from elephant's trunk to sea anemone. It loses contact with the seminal pool and hence cuts off the upwards escape route for the sperm.

Once the cervix has withdrawn, those sperm still in the pool are condemned to ejection and an early death. About fifteen minutes after ejaculation, the pool begins to decoagulate and becomes more watery again. Our story will be one of men's bodies forever trying to make the best of a bad job, while the woman's body outsmarts and outmanoeuvres them at almost every turn. But this at first sight uninspiring scene does give us an Scene 4 opportunity to watch men doing something fairly impressive.

A man may not look particularly sophisticated at the moment of Topping Up ejaculation, but something remarkable is, in fact, taking place. Each time he has intercourse during routine sex, he introduces no Over the next two weeks the couple became quite active, sexually. How does such The coolness of the woman's fertile week evaporated. Both restraint help him in his pursuit of reproductive success? To partners went through a phase of anticipating and enjoying their understand what the man is trying to do, we have to follow further sexual activity more than they had for about a year.

After making those sperm we last saw swimming through the channels in the up on the Saturday night, they had sex twice on the Sunday, once woman's cervical mucus. Half an hour later, they even tried again. He through her cervix into the womb. Except when she is pregnant, had an impressive erection but, despite ten minutes of intermittent her womb is roughly pear-sized as well as pear-shaped.

As with thrusting and encouragement, he eventually had to accept that he the vagina, the walls press closely together, so there is little space wasn't going to ejaculate. Then they missed a few days. Once in the womb, sperm swim close to the walls and are Wednesday night was the woman's weekly night out with helped by the womb to reach its top, the widest part of the pear: in girlfriends; Thursday night the man's weekly night out 'with the effect, they surf-board, carried on the crests of muscular ripples boys'.

On both nights, when the reveller eventually crawled into passing along the womb's walls. At the top of the womb on each bed, the partner was asleep, or at least pretending to be. On Friday side where horns would be if the pear shape of the womb were a night, however, they had sex and did so again on both Saturday bull's face is the opening to a narrow tube, the oviduct. Although and Sunday. The next week followed a similar pattern, until the there are two oviducts, only one will contain an egg during any woman's period began on the Saturday morning.

Then they given menstrual cycle. Once out of the womb, the sperm swim a abstained until the following Saturday, by which time her short distance along an oviduct until they reach a rest area. Here menstrual bleeding had finished. Back in the cervical mucus, another set of sperm swim along more diagonal channels and stream into tiny crypts in the wall of F ew couples have their routine sex at absolutely fixed intervals.

In the four weeks we have been following this couple, they have had penetrative sex ten times and the woman the cervix. These sperm also, once in the crypts, cease swimming, settle down, and conserve their energy. Over the next four to five days they will gradually wake up and re-enter the cervical has been inseminated nine times. But the time interval from one channel. Then they, too, will complete their journey through the intercourse to the next has varied from as short as thirty minutes mucus, surf-board through the womb, and head for the rest area in albeit without ejaculation or seven hours with ejaculation to as the oviducts.

The final set of sperm simply stay in the cervical mucus. Eventually they die ensure a continuous passage of fresh sperm to the rest areas in — or are killed. Their lethal assailants are the marauding hordes of the oviducts. If he injects more sperm than are needed, they white blood cells which are unleashed by the female from the walls will be wasted; the reservoirs will overflow and even more of her womb within minutes of insemination.

As they advance sperm will simply hang around in the cervical mucus and fall through the cervical mucus, these killer cells engulf and digest live prey to the female's white cells. There is also a danger that too and dead sperm alike.

At their peak the white blood cells can many sperm will arrive in the oviduct and, with a surfeit of the match the numbers of sperm, but within twenty-four hours of chemicals that they carry on their heads Scene 7 , actually insemination these hordes have gone, leaving behind much smaller kill any egg that may be present. On the other hand, if the man numbers to complete the mopping-up operation.

Multitudinous doesn't fill the reservoirs enough, too few sperm will arrive in though the white cells may be, they do not pursue sperm into the the oviduct or the reservoirs will dry up prematurely. The cervical crypts. Of these, the woman will eject about million in the reservoirs. This he seems to do with remarkable precision. A few hundred sperm may go straight to the oviducts The adjustments we are talking about are roughly as and about a million may first go into the cervical crypts to form follows.

If more than a week has passed since the man last reservoirs, leaving in order to complete their journey to the inseminated his partner, her reservoirs will be empty and he oviducts over the next five days. In all, about twenty thousand will introduce a full load of sperm, say four hundred million. Of these, perhaps just over a million will fill the reservoirs. If The remainder, those not ejected in the flowback, clutter up the the gap is only three days, he will introduce about two cervical mucus, eventually to be mopped up by white cells or hundred million, and half a million will top up the half-empty carried by the slow, glacier-like flow of the cervical mucus Scene reservoirs.

If the gap is only three hours, he will introduce 3 back into the vagina. Even after half an hour, he may find it difficult million sperm when only about a million enter reservoirs. But all is to ejaculate, like the man in our scene. His body is effectively not what it seems. As far as topping up the woman is concerned, saying that there is no point. His partner's reservoirs are full the important point is that the size of the reservoirs depends on and any sperm ejaculated will simply be wasted.

If he puts in only two Our couple have had penetrative sex ten times in the four hundred million, then the reservoirs will be only half as full as if he weeks we have watched them. In that time, about three put in four hundred million. So precise is the man's ability to top up his partner that them to produce a steady passage of fresh sperm through each if they had doubled their rate of intercourse, or if they had oviduct over a period of about five days.

This traffic probably halved it, it would have made scarcely any difference to the peaks about one to two days after insemination, then gradually total number of sperm she would have received. This is where topping up comes in. If the male can keep the top up their partner. How do they do it? To answer this, we reservoirs of sperm in the cervical crypts topped up, he can need to understand more about both the architecture of the male reproductive tract and the mechanics of ejaculation.

Each sperm will then spend a man is standing in front of you waiting to be examined. His genitals further two weeks queuing in the epididymis and up to a further five are at your eye level. Note his navel, his pubic hair, and the penis days or so in the vas deferens. There is a little queue-jumping as hanging down, slightly askew, in front of the scrotal sac containing some young sperm from the back of the queue are shunted ahead his pair of testes.

Hold his flaccid penis in the palm of your right of older sperm at the front, but this need not concern us here. Now, let's follow what happens to our medical model as he goes The rather swollen knob at the end of the penis is called the glans off with his two columns of sperm and has intercourse. While he and, right in front of you, is the vertical, slit-like opening of the was standing in front of you he had no sperm in his urethra, but two urethra.

Through this, the man both urinates and ejaculates. Fix sperm tubes containing in total up to about a thousand million the line of his urethra in your mind. It runs in a straight line from the sperm.

Nothing will change when his penis becomes erect, not opening slit, back through the penis shaft, into his body and up to even during the early stages of penetration and thrusting.

Fix your eyes at the top of his pubic hair and Eventually, though, sperm will be shunted out of each sperm tube imagine you can see inside to where the urethra and the bladder and into the urethra.

A round sphincter that normally prevents urine join. Just below this point, the urethra is joined from left and right leaking out of the bladder also prevents sperm from entering the by two tubes. These tubes run all the way down to the testes and bladder.

The man's urethra is now loaded, ready to fire. Where these While loading, the man will feel a pleasurable urgency at the base tubes join the urethra, they are surrounded by a walnut-sized mass of his penis.

He will also know that ejaculation is imminent. This is the prostate gland, which produces the bulk of the how imminent is, to a limited extent, under his conscious control. When he finally ejaculates, seminal fluid pours from his prostate So where do these two columns of sperm come from?

Even as into his urethra. Then muscles contract and the mixture of fluid and the man stands in front of you, his testes are a hive of activity. By the time the sperm are mature and fit to be ejaculated, Now, it is not difficult to understand how the man's body controls they have already been herded into the single column of sperm the number of sperm he ejaculates.

Depending on how many of his from their testis. They are in the sperm tube, but they are still in, or loading muscles work, and how strongly, he can shunt any length rather on the surface of, the testis.

The sperm tube changes in of each of his sperm columns out of their tubes and into his character along its length: in the testis the tube is called the urethra. Even after loading, his body can change its mind. By epididymis, and from the testis up to the urethra it is called the vas varying the number of spurts, usually from between three and deferens. Whereas the vas deferens is more or less straight, the eight, he can ejaculate a different proportion of the loaded sperm.

Any sperm and seminal fluid left in his urethra after ejaculation can Once the sperm are in the epididymis they are, in effect, simply be flushed out at the next urination. Each time the man ejaculates some Of course, somewhere there needs to be a link between the of his sperm, the rest shunt forward.

As part of the front of each man's brain, which keeps track of when he last inseminated his queue is lost through ejaculation, newly mature sperm join the partner, and his genital musculature. Given such a link, it is not back of the queue in the testis.

Slowly he had begun to enjoy himself. Nobody suggests, of course, that a man has conscious control They weren't very practised at having sex with her on top, and a over sperm number. In the midst of thrusting and at the point of couple of times he had slipped out. She had had to work quite loading his urethra, he does not ask himself consciously, 'Is this a hard but eventually he had ejaculated.

Tonight, they had tried the hundred-million occasion or a four-hundred-million? When the Eventually, they had reverted to their usual missionary routine. This leaves his conscious mind free to that would change her life for ever.

She had ovulated Wilier that concentrate on his thrusting — and the woman. As it arrived in the fertilisation zone, three fertile sperm arrived simultaneously.

They began to burrow through the outer layers of the egg. Two of Scene 5 them were delayed for a few seconds as they bumped into each other, attempting to penetrate the same point in the egg's defences. Conception The prize of fertilisation went to the third sperm, which had a clear run, unhindered by any others. By the time another sperm It is Friday night and twenty-one days have passed since the arrived only a few seconds later, the egg had put up its barriers beginning of her last period — bleeding that signalled a second!

The egg had been fertilised by the first month without conception. Briefly, the couple had feared: for sperm to get through. Three months after giving up contraception, their fertility. They were calmed, however, both by the the woman had conceived. Two hundred and fifty days after that medical investigation.

With these reassurances, they had put the she would give birth. The identity of the father, however, would month behind them and started afresh. Now, they have just had never be known. For the sperm waiting in her oviduct that Friday sex and are drifting off into post-coital sleep.

Tonight, she won't night had in fact been from two different men. In the past two weeks, their sex life had more or less followed the routine they had established since giving up contraception. Sex on Saturday, Sunday and sometimes, as this week, also on Friday had become the norm. This week, though, had been T here is one final phase to the odyssey of fertilisation — a phase that can be critical in a man's and a woman's pursuit of reproductive success.

On Wednesday night, as soon as she had got In previous scenes, we have followed sperm from their earliest into bed after returning from her weekly night out, she had life in the testes to the moment they are shot into the woman's stroked his body until he awoke and had played with his penis vagina.

We have watched them attempt to escape from the until he was erect. Then, she had sat astride him and manhandled seminal pool, migrate through the narrow channels of cervical his penis into her vagina.

There we left them, waiting for the final stage of their layer, the zona, which is the outer membrane of the egg itself. Under the zona is a narrow space which surrounds the final, most Sperm may rest in an oviduct for as long as a day and, at any vulnerable barrier, the vitelline membrane. One Using its head, the sperm hacks its way through the cumulus by one, they wake up and swim further along the oviduct.

Their cells. If successful, and it reaches the zona beneath, it sticks the initial destination is a region in which, if an egg is present, side of its head on to the membrane with chemicals.

With this fertilisation can occur. But usually no egg is present, and the chemical attachment serving as an initial purchase, the sperm sperm simply pass through and eventually die. The behaviour. Its tail starts to beat more vigorously and, once it lashing tail provides the force to push the sperm forwards.

Finally, arrives, it often swims frantically in circles or figures of eight. At if this sperm is the first to get through the zona, cross the any one time, the fertilisation zone may contain anything from underlying space and touch the vitelline membrane, it is engulfed one or two to up to a thousand sperm, all looking for the egg that by the egg in a welcoming embrace. Having embraced one sperm, usually never comes. After a while, they leave the zone, one by the egg passes a chemical message across its surface and, within one.

As each leaves, its place is taken by a new, fresher arrival seconds, becomes impenetrable. If you are a human sperm, there from the rest area. Having left the fertilisation zone, each sperm is no prize for coming second. This then travels to fuse with manage because the end of her oviduct gapes open, its opening the similar heart of the egg. Fusion of the DNA from sperm and surrounded by finger-like projections. A new person has been conceived, with A short distance away from the end of each oviduct, suspended characteristics that are a subtle mixture of his or her two parents.

Tiny We know with certainty the mother of the child in our scene. As we saw, in those few critical days before towards the black hole of the oviduct. Like a waiting hand, the she ovulated the woman had collected sperm from two men — her finger-like projections funnel the egg into the tube.

From here, the partner and her lover. To see what happened, and to work out who egg begins its five-day journey down towards the womb. We are about to To achieve fertilisation, a sperm has to do more than simply witness a sperm war. The outer line of defence, the cumulus, is a thick layer of shapeless cells which the egg has brought with it from the ovary. Now, however, meeting him out of the blue, many of her old feelings returned.