Blake Morrison: Anyone want to live for ever? I do

It's ironic, if wholly predictable, that the fiercest critics of last week's Lords vote to allow the cloning of human embryos should have been "pro-life" campaigners. Pro-life? Shouldn't that mean wanting people to have the healthy lives that stem-cell research will eventually make possible - rather than requiring them to go on suffering Parkinson's, heart disease, arthritis, hepatitis, diabetes, strokes and cancer?

It's ironic, if wholly predictable, that the fiercest critics of last week's Lords vote to allow the cloning of human embryos should have been "pro-life" campaigners. Pro-life? Shouldn't that mean wanting people to have the healthy lives that stem-cell research will eventually make possible - rather than requiring them to go on suffering Parkinson's, heart disease, arthritis, hepatitis, diabetes, strokes and cancer?

And doesn't being pro-life also mean wanting people to have long lives? For that's also a part of the cloning enterprise. A time may come when we can keep ourselves from pegging out till we're good and ready - or not at all.

Couldst thou make men to live eternally

Or, being dead, raise them to life again,

Then this profession were to be

esteem'd.

So it's said in Marlowe's Doctor Faustus. The esteemed profession of medicine has more immediate concerns than longevity. But as fatal diseases are slowly conquered, and individualised "body repair kits" protect us from getting decrepit, a significant extension of the human life span will surely follow.

Already geneticists and bio-gerontologists are predicting that human life expectancy will double by 2050 (just too late for me). A few say immortality is feasible, too: "I predict we'll have the ageing gene in our hands very soon" (Ron Hart, US National Center for Toxicological Research); "I really do believe that it is theoretically possible to have absolute immortality" (Professor Lee Silver, Princeton University); "I think that we may be able to see the first immortal human some time in the late part of the century, say, 2075-2100" (Dr William Haseltine, Human Genome Sciences). It sounds like science fiction. But then science today is like fiction. In the long view of history, those of us living now may turn out to be pitiful museum pieces, the poor terminal ones who went a generation or two before the problem of death was finally cracked.

A bit of scepticism is in order. The quacks and charlatans of perpetual youth are as common in modern science labs as they were in Ben Jonson's day. Pharmaceutical companies have too much invested in the snake-oil of eternity to be scrupulous. And history teaches us that for every medical advance there's also an unforeseen step backwards; who in 1950 could have predicted Aids, or BSE, or the resurgence of TB? All the same, it's clear that huge advances are being made.

At the University of Sussex, Michael Rose has created so-called "Methuselah" fruit flies. At the University of Newcastle, Professor Tom Kirkwood has been refining his "disposable soma theory" to show that "ageing is neither inevitable nor necessary". In US labs, important work is being done on "telomeres", a piece of DNA at the end of our chromosomes which acts like the plastic tip at the end of a shoelace to prevent fraying. Each time a cell divides, the telomere gets shorter - until it ceases to offer protection and the cell begins to die. But scientists have found a way to rebuild telomeres, by introducing an enzyme called telomerase (which adult cells can't produce), and in lab conditions - in a Petri dish - they have been able to put cellular ageing on hold.

The traditional view is that to live beyond 120 would be unpleasant, and immortality a nightmare. The prospect of death is supposed to sharpen our appetite. "All's well that ends," wrote the poet Robert Lowell, abbreviating Shakespeare. Faust's Mephistophelean pact may earn him an extra 24 years on Earth, but the time flies by so quickly that it isn't worth the price of his soul. Then there are the Struldbrugs, or immortals, in Swift's Gulliver's Travels - withered, senile, depressed and solipsistic - who endure all the infirmities of old age as well as "the dreadful prospect of never dying".

The Struldbrug story is a variation of the Greek myth of Tithonus, whose misfortune was to be granted immortality but not eternal youth. Third-millennial immortality might not leave mankind in such a fix - in theory, future generations could simply buy new body parts and perpetually regenerate themselves. But that still leaves the problem of psychological adjustment; wouldn't knowing one can never die be a kind of death in itself? Isn't kicking the bucket a fundamental human right? Having a brain transplant every 100 years or so might make eternity easier to cope with. But would that really count as immortality, if it meant the extinction of the person - or personality - that existed before?

Immortality is more than most of us can get our heads round. So what about the nearer prospect of longevity: how would it be to live for 150 years? Here I part company with Swift but also with evolutionary hardliners who say the human body is designed for obsolescence because once we've had children we're no longer useful and must die to prevent the world from becoming overcrowded. It's as true or truer to say that the human body is programmed for survival, and that the human mind is constantly seeking ways to extend life. Genetic cutting-and-pasting will soon allow us greater control of our destinies. Modified, we can live longer. And few of us, given the choice, would elect to have lives as short as our forebears had. Does 70 seem old any more? Do 75 and 80? This 50-year-old doesn't think so.

Some people reach a point where they have had enough - not just because they're physically run-down but because life holds no pleasure or surprise.

"O! let him pass," Kent says of the dying Lear, "he hates him/That would upon the rack of this tough world/Stretch him out longer." But if we could age at half the speed we do now; if giving birth at 60, and having great sex at 95, weren't freakish but the norm; if the rack of pain and infirmity were withheld until the last months; if we expected to live to 150, not 80, and adjusted our pace accordingly - then what's the drawback?

Oh, but the important thing is to be truly alive while you are alive, people say. True enough. But why not be truly alive for longer? Carpe diem - seize the day. But couldn't we seize tomorrow too? Living on needn't mean grey-haired caution and niggardly hoarding. There'd be the chance to do more, feel more, think more, be more. "If I could have my time again," people say. Well, perhaps in future they will, and live their lives twice over first time round.

Writers hope that their books will give them a form of afterlife. But posterity is unpredictable. And is immortality worth having if one isn't around to enjoy it? (I don't see Shakespeare getting much pleasure from his.) To have to die in order to live for ever isn't the best of deals. Far better to enjoy longevity in the flesh. Should weariness and self-loathing set in, there's always the get-out clause of suicide.

Forty years ago, the hero of Kingsley Amis's novel Take a Girl Like You decided that there was "quite a good chance of his never actually being called upon to die at all. Those medicos would probably come up with something in the next decade or so". Well, they didn't, they haven't. The present consensus is that no one gene is responsible for ageing (there may be as many as 7,000), and that postponing or cancelling death is much more complex than taking out a single offender. But already we are living longer, and our children's children can surely improve on our modest efforts.

Oily fish, regular exercise (including sex), Ibuprofen, hormones like melatonin and DHEA - the popular wisdom is that these are good for longevity. But cell banks and body repair shops will offer more. The sooner the better, I say. Who, offered a healthy few additional years, would refuse? Not Faust. And not me.