We've known for almost all of this century that there's nothing chemically special about life. The difference between living and unliving things is simply in the way that their molecules are arranged. In principle, and given the right chemicals, you can make a kind of biological Meccano kit with which you can build any animal. But it is still extraordinary to think that scientific understanding has progressed to the point where Dr Venter thinks he can assemble the minimum necessary kit for making life.
We can all imagine what the news from California should have meant: men in white coats standing over a bathtub full of chemicals, pouring from test tubes of DNA and stirring until the bath began to heave and wriggle and little things with legs and tails try to climb out up the sides. But it won't be like that, and this is for reasons that illuminate the limits as well as the powers of scientific knowledge.
The first problem is the nature of DNA itself. Despite all the talk of it as a molecule which copies itself, it can't copy itself except when it is part of a cell and surrounded by the right proteins, which come into contact with it in the right order. People talk in shorthand of DNA replicating itself, but this is no more true than saying that my word processing program can print without being installed in a properly equipped computer.
Dr Venter thinks he has designed a string of DNA containing 300 genes which can specify a cell that will build more of the same string of DNA. If it works, this cell will be a form of life that has almost certainly never existed before. Since he has an excellent track record in the manipulation of DNA, people are saying that, if anyone can do it, he can. And even if he fails, it is almost certain to be done by someone within the next 10 years. The difficulty is that this new form of life needs old life as its raw material. DNA is not enough. It can't copy itself. There must also be a cell which can use the DNA to make more of the same.
What Dr Venter seems to be planning is to use a blender, rather than a bathtub: instead of dropping his strands of 300 genes into a chemical soup, he is going to drop them into chopped up cells of Mycoplasma genitalia, the micro-organism from which they were originally derived. This is similar to the way in which Dolly the sheep was made.
It's not quite reproducing the way in which life must have started on earth, because on the primitive earth there were no cells, and probably no DNA either. That whole mechanism must have evolved from simpler chemical precursors. But what he proposes to do is going a long way back towards the beginning of life: Dr Venter will take two sets of chemicals that are indisputably dead and, by mixing them, produce an organism that is alive (even if the life of a bacterium lacks interest and excitement).
That doesn't make him Dr Frankenstein. There's a huge leap to be made from creating life to designing it; and even if the experiment works, no one knows in detail why these 300 genes should be the ones necessary to create a life form. Dr Venter himself says that he only knows what 200 of them do. The other 100 seem necessary to a functioning cell, but he doesn't know why.
Human beings are, of course, infinitely more complex. We have between 70,000 and 80,000 genes, though it will take decades of work to find out how many there are exactly and what functions they perform. Since we already have a perfectly good and pleasurable way of creating human beings without any scientific apparatus at all, our interest in human genetics lies in designing rather than creating, and for most interesting purposes that will require a lot more knowledge than is in sight today.
Yet the road ahead is clear in principle. There is no longer anything special about life that science can detect. The difficulty that these discoveries raise is that we want science to reinforce our moral intuitions, and it's not often very good at the job. It is beginning to look as if the sanctity of life must be a religious illusion. But this is not necessarily the case.
An alternative to the idea of morality as a religious illusion is that it is just an evolutionary illusion - evolved to keep our ancestors alive by paying respectful attention to things large enough to eat us. Consequently, our intuitive idea of "life" is something big enough to see, but this intuition could hardly be more wrong. Most of life, through most of history, has always been single-celled; and it's almost as difficult for a human being fully to imagine this as it would be for a bacterium to conceive of the sanctity of human life.
But there is an alternative to both these rather ghastly perspectives. After all, we can't reasonably expect the universe to take any notice of human beings, even if it were the sort of thing that could take notice. Life is special only to other living things, and human life is special to human beings.
We do not love, or even hate, our fellows for their chemical constituents. We love them because they're loveable, and hate them because they're the wrong sort of human: Serbs, Muslims or whatever. The massacres in Kosovo are a much greater threat to human dignity than anything brewed in Dr Venter's test tubes.
Andrew Brown's book `The Darwin Wars' will be published by Simon & Schuster in March