I was sitting in a cafe yesterday, doing something I don't normally do - chatting about sperm. In fact, I was chatting about sperm with another guy. We were talking about the news that, as from now, sperm can be cloned in a laboratory.

"It's only mice, so far," I said.

"How do they do it?"

"They take a bit of a stem cell, I think, and ..."

"Splice it."

"Right."

What interested us much more, though, was the response, in various newspapers and broadcasts, to the news of this research. The response, essentially, was the question "Will this make men redundant?" In other words, when the technology develops to the extent that it can be used on humans, will a significant number of women want to be fertilised without using sperm that has been acquired by the old-school method?

And, if they do, how will this make men feel?

Pretty bad, was my initial feeling.

After all, biologically speaking, a man is two things. He is, first, a sperm-making factory, and, second, a sperm-shooting machine. So it would not be surprising if, on some level, men felt put out - a little emasculated, even - by the "artificial" sperm production technique. Soon, if you want sperm, you will be able to get it without going to the traditional sperm factory. You might say that, for men, this is rather like owning a cotton plantation, and reading about the discovery of nylon.

Maybe some men will be relieved to read that, so far, the new cloned sperm are a bit like nylon. They work - sort of. But when you make something out of them, the end product is less durable and more likely to be faulty.

Earlier medical research on sperm, which showed that it could be frozen and then implanted at a later date, was, if anything, comforting. This meant that you could freeze your sperm, and then, if you died, your genes might still have a chance of being passed on. It also meant that if, at a later stage of your life, you lost your capacity as a sperm-shooting machine, nobody need know. Well, nobody outside your close family, anyway.

Cloned sperm, of course, is a different matter. One day, some time in the near future, the scientists might get it right. And then what? Since the dawn of time, men have always known that, whatever they do, however badly they behave, they are still the only place to go if you want sperm.

Well, possibly not for much longer. Won't this affect us, somewhere deep inside our brains?

Maybe a little bit, we decided. And then we tried to imagine what would happen if the situation were reversed. If scientists discovered a way of cloning eggs from stem cells, would men even consider the possibility of doing without women? Would newspaper articles trumpet the possible redundancy of the female half of the species?

"Never," I said. "Men would never want to get rid of women."

"Yes, but that's not to say they feel the same way about us."

"How do you mean?"

"Well, look at how we revere women and their eggs. And compare that with how sperm is depicted."

I could see his point. How is sperm depicted? We see it as messy, at best. And also a bit creepy, a bit sinister. The presence of sperm - or semen, the fluid in which it is contained - is a potential violation. It is an insult. Remember the scene in Fight Club in which a restaurant worker adulterates the food with his semen? And the follow-up article in which the author of Fight Club, Chuck Palahniuk, tells the story of how he was approached by a waiter who had seen the film of Fight Club, and who told him, "Margaret Thatcher has eaten my sperm."

Do we ever see sperm in a good light? When it appears in cinema, we wrinkle our faces in disgust. We see it in Atomised, the film version of the novel by Michel Houellebecq, when a pervy teacher masturbates on to an essay written by one of his pupils. And in the final scene of the film Happiness, when a teenage boy masturbates out of a window. Then he ejaculates, and the camera tracks the progress of a dog. The dog eats the semen. Todd Solondz, the director, seems to be signing off with a smirk, and also a visual "yuck!"

It gets worse. The feminist Andrea Dworkin saw a link between the idea of ejaculation and spending money - after all, to "spend" means to ejaculate. And, while women "use money especially for adornment so that they will be desirable to men", men, on the other hand, spend money the way they ejaculate - for pleasure. For Dworkin, women buy beauty, and men buy women. She goes further: "Violence is male; the male is the penis; violence is the penis or the sperm ejaculated from it." Now think of the traditional "cum shot" in pornography. It's a demonstration of Dworkin's thinking. It's about power and arrogance. It's nasty.

The gentlest depiction of sperm I can think of comes from Woody Allen, in the film Everything You Ever Wanted To Know About Sex, But Were Afraid to Ask. Here, we see Allen in the role of an anxious sperm as he prepares to be ejaculated into the great beyond. He's worried about all the rumours he's heard, particularly the one about being slammed into a vast wall made of rubber. You laugh, partly because you feel sorry for him; you know that, in the brutal Darwinian world of sperm competition, he will never make it.

To understand the relationship between a man and his sperm - to understand, that is, why he is just like a walking, talking sperm - you have to go right back to the most primitive form of life you can imagine. Think of prehistoric fungi in the primordial swamp. These early forms of life were not divided into males and females; they did not have male and female reproductive cells (or gametes). They just had plain gametes. When sexual reproduction occurred, it was between equals. And then something important happened, something that, countless millions of years later, would make men behave badly - like, say, John Prescott. But I'm getting ahead of myself.

In his classic book, The Selfish Gene, Richard Dawkins tells us about the process that turned equal-opportunity gametes into male and female sex cells. Imagine, for a moment, that the primordial soup is a kind of office party peopled only by one sex, and that these one-sex gametes are all the same, and that they all fancy each other. As Dawkins points out, they would be roughly the same size. They would each contain 50% of the genes needed for reproduction, and enough nutrition to feed the growing embryo.

But, Dawkins wonders, what if some of the gametes happened to be just a little bit bigger than the others? These cells would have a genetic advantage, because they would contain more food for the embryo. But this would have had an unbalancing effect on the gamete population. Now, a smaller gamete would have its own distinct advantage. As long as it could dock with a bigger, food-carrying gamete, it would not need to be so big and cumbersome. According to Dawkins, then, natural selection favours two types of sex cells - large ones with plentiful food supplies, and small ones with fast propellers. Medium-sized gametes have no advantage, and so they die out.

And so, several million years later, here we are: men are machines for making and firing billions of tiny, competitive, kamikaze sperm. Women, on the other hand, are the creators of a limited number of precious, embryo-nurturing eggs. Sperm are tiny, high-risk life-forms; they are expendable; they must put all their chips on one number; they must be bull-headed and blindly confident.

Eggs are scarce. Eggs don't want to move far from home; if they do, it's curtains for them. Sperms are buccaneers, adventurers. The last thing they want to do is stay at home. Does any of this sound familiar? Well, as Dawkins says, you just have to look at the relative sizes of sperm and eggs to reach the conclusion that "it is possible to interpret all the other differences between the sexes as stemming from this one basic difference."

So how do we behave, we sperm-carriers? What does our status as sperm-shooters do to us?

I think we all know the answer to that question: being sperm-vectors makes men want to behave like John Prescott. And Mick Jagger, Darren Day, Jack Nicholson, John Major, and Bill Clinton. Having millions of sperm puts certain men at an evolutionary advantage, yet this is something which, in a civilised society, we expect them not to cash in on. Still, as human biologist David Buss, author of The Evolution of Desire, would tell you, guys behave like guys because they are full of sperm; those who behave less like guys are less likely to pass their genes on.

When a man is away from his sexual partner, the number of sperm he produces dramatically increases. This is because, in evolutionary logic, his partner may have been unfaithful to him - she may be carrying another man's sperm inside her. So he automatically increases production, from 400m sperm per ejaculation to as many as 700m.

What does all this mean? It means that, since the Stone Age, males wanting to pass their genes on can do two things. Having a boundless supply of sperm, they can spread their seed far and wide, hoping that some of it will take root and flourish. Or they can settle down with a single mate and hang around, making sure their offspring is fully catered for. And then, when they have the chance, they can try to impregnate somebody else on the side.

Sadly for civilised society, this is an adaptive trait. It must be the case, because, if you're a guy, your genes are bound to be replicas of the genes of the most successful impregnators from the past. You are descended, in other words, not just from shaggers, but from the biggest shaggers in history.

Here's a good thing you can say about sperm: they may be the reason for the female orgasm. One theory is that having an orgasm is likely to keep a woman in a reclining position after having sex, thus minimising "flowback".

Another theory, as described by David Buss, is that "women's orgasm functions to suck up the sperm from the vagina into the cervical canal and uterus, increasing the probability of conception."

Now, of course, things might be about to change. With cloning a definite possibility, might the gene that favours promiscuity - the shagger gene - gradually be phased out? Now, if the research develops, it will be possible to clone sperm from any kind of man. Quiet, unassuming ones, for instance. The type who, when you invite them in for a coffee, just want the coffee.

"Would that be a bad thing?" I said, sipping my coffee. My friend shrugged.

Two guys, sitting in a cafe, talking about the future of sperm. We weren't too worried. We could handle it.