Soon, when a child asks where babies come from, the answer will be 'the internet', says Robin Baker

Imagine the scenes. A woman convinces her teenage daughter to be sterilised and to bank eggs for reproduction by IVF later in life. A mother and son sit in a "reproduction restaurant" choosing his ideal gamete partner from an internet database. A man who cannot produce sperm sires a child on the other side of the world - with another man. Is this the future of reproduction. Is this what will happen when ancient urges meet future technology?

The phrase "ancient urges" conjures up thoughts of wanton promiscuity and public sex. Most of us, of course, do not run our reproductive affairs this way - but the beast is in us nonetheless, a sexual legacy from the past million years. But as humankind strides into the 21st century, that beast is under threat.

How will it cope with the developments that have become part of our reproductive destiny: IVF, cloning, surrogate mothers, nucleus transfer, gamete banks and frozen embryos, or even paternity testing and child-support enforcement? These developments could trigger a social revolution as far-reaching as any in human history.

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Two developments appear likely: lone-parent families - and the blended families that arise when lone-parent families cohabit - will become the social norm; and the divorce of sex from reproduction, which is already nisi, will become absolute.

Current social and political attitudes to lone-parent families are negative. Moreover, owing largely to financial hardship and lack of suitable day-care provision, such families often suffer compared with more traditional nuclear families. Despite this, lone-parent families continue to multiply throughout the industrial world. And the evidence is that with adequate finance and day-care, lone-parent families can be as successfulas any.

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The nuclear family is a biological institution, not some ideological pawn of religion or politics, and it is based on biological distrust. To the romantic, men and women live and sleep together because they love each other. To the cynical biologist, they do these things to make it difficult for their partner to have sex with anybody else. Like most biological institutions, the nuclear family will form under some conditions and disintegrate under others. And the modern social environment will change into one in which lone parenthood rather than the nuclear family appeals to both men and women.

Vulnerability is the biological cement that binds couples; independence is the force that weakens those biological bonds. Beyond a particular point, these bonds disappear - and this is where the modern environment is leading. Child-support legislation will free women from the fear of destitution. Routine paternity testing will free men from the subconscious fear of unknowingly raising another man's child. Together, these two developments will free people to pursue their individual ambitions, hastening the demise of the nuclear family and promoting the lone-parent family. Single-parent families will become the majority of the electorate - governments will become their hostages.

But this is only the beginning of the social revolution. The burgeoning lone-parent society will find that technological developments ease reproductive life, enhancing rather than eroding the new social structure. Most importantly, these developments will lead to foolproof contraception and a complete separation of sex from reproduction as fewer and fewer babies are conceived via intercourse.

Assisted conception techniques herald an end to infertility. That is, after all, why they were developed in the first place. But just as bottle feeding began as a treatment for those who could not breast feed then rapidly transformed into a commodity for those who did not want to breast feed, so too will assisted conception techniques be grasped by lone parents and transformed from treatment into commodity. The process has already begun. Before long, the trickle of single women to sperm donor and IVF clinics will become a flood.

Combine the demand for assisted conception with that for a foolproof, user-friendly and health risk-free method of contraception and the result is the "BlockBank" system - having tubes blocked at puberty and banking eggs, sperm and cells for reproduction by IVF later in life. The way will be open for individuals to become lone parents by commissioning children when and with whom they want or can afford. They could negotiate to obtain gametes from people they know or - depending on finance - from the rich and famous, and then use them to reproduce via IVF with their own gametes. The freedom to integrate family planning with a successful career will become total.

But if a person is commissioning gametes but not necessarily living with the baby's other parent, there is little incentive to have every child with the same person. Increasingly, each person's family will be from a mixture of "second" parents. And because the technology of gamete manufacture will allow sperm to fertilise sperm and eggs to fertilise eggs, for those who wish it, homosexual reproduction could be commissioned as readily as heterosexual.

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Of course, love, pragmatism and the need for companionship will often lead two (or more) lone parents to live together to raise children within blended families - as many do already. Also as now, cohabiting couples will probably have sexual relations - but because of the BlockBank system they will not necessarily have children together. This separation of sex from reproduction, combined with computer technology, will open up a bewildering range of choices.

In the United States, donor sperm and eggs can already be obtained with relative ease. Some services even combine express-mail delivery with worldwide web sites that allow prospective parents to screen for donor characteristics such as height, weight and eye colour. Assisted reproduction technology is a growth industry in the US.

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In the future, such gamete selection is likely to take place over the internet. Not least because there will be a need for worldwide regulation of the selection process - for example, to prevent the biological effects of inadvertent incest. The establishment of something like an international Gamete Marketing Board would seem to be essential. Then, just as the 20th century saw the formation of internet cafes, so too could the commissioning process of the 21st century see the establishment of reproduction restaurants - places where people go to eat, drink and browse their reproductive possibilities.

Men as well as women will be able to commission a family by purchasing a woman's eggs from the GMB and hiring a surrogate mother. Biologically, though, the beast within men is programmed more for itinerant sexual activity than for long-term commitment to parenthood. For most men, reproduction will stem from negotiation - persuading women to purchase their sperm in exchange for financial support.

The process raises many intriguing questions. Will genetic parents want to keep in touch with their global family? Will people show an interest only in the children they commission and raise, or also in the children other people commission from them? What financial and contingency arrangements will be needed for the raising of commissioned children? Should people pay for the maintenance of children other people have commissioned from them or only for the children they themselves commission? Would all reproduction become a matter of financial negotiation?

Many people are terrified by such a social revolution, deeming it unnatural, demeaning, a threat to human dignity or contrary to the will of God. A similar furore greeted bottle-feeding, artificial insemination and IVF. But society has survived and even progressed on the back of such dastardly innovations. After all, clothing, shaving, depilatory creams, deodorants and bottle-feeding are all "unnatural". So, too, are supermarkets, cars and aeroplanes. Yet how many people, in the name of natural human dignity, walk naked, hairy and smelly into the countryside each day to forage for food?

It would be easy to be pessimistic about the future, to lament the passing of the familiar. But there is no need. The human species will continue and will probably even be enriched by the changes to come. When ancient urges meet future technology, there should be no winner or loser. Instead the two are likely to join forces to propel human reproduction through the next 100 years of its evolution with profit not cataclysm.

Robin Baker, former reader in zoology at Manchester University, is author of Sex in the Future: Ancient Urges meet Future Technology, published this month by Macmillan, Pounds 12.99.

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