The lab

The "Brave New World" brigade is worrying unnecessarily about human cloning
April 19, 1996

The innocents from the Roslin Institute near Edinburgh, who announced on 7th March that they had produced two identical Welsh mountain sheep, should not have been surprised that they triggered off yet another bout of agitation about research in genetics and embryology. Most anxiety in this field has recently centred on the use of pigs' hearts as transplants for human patients. It is a long time since there was a fuss about what is called "cloning," or the artificial production of individuals which are carbon copies of each other. As the seasons come and go, cloning was no doubt due for its turn again.

Even so, the hyperbole of the past few weeks has splendidly outdone science fiction. References to Brave New World have been routine (in The Times, Roger Scruton cleverly used it both to make his point and put down Aldous Huxley's novel). The reaction has been that, now that they have done it with sheep, it is only a matter of time before they can do it with people. And then it will only be a matter of time before the rich and powerful find embryologists and physicians prepared to break the law in the interests of their genetic succession.

The people at the Roslin Institute must be wishing that it were that simple. Their purpose (they make no bones about it in their published paper) is to find a vehicle for the rapid introduction of altered genes into farm breeding stock. Given the seasonality of sheep (this is the lambing season), conventional techniques allow only the slow spread of an advantageous gene through a flock.

The extent to which the Roslin group has solved this problem is far from clear. The crux of what they have done is to extract from a nineday-old sheep embryo the tissues destined to become germ cells (the progenitors of ova and sperm); to induce cells from those tissues to multiply in the laboratory; and to show that when cells of that kind are fused with mature sheep oocytes from which the chromosomes have been removed, the result is a cell which functions as if it were a newly fertilised sheep ovum.

In other words, the fake fertilised ovum can be put into a sheep uterus (at the right season) in the expectation that it will grow to term, becoming a lamb after six months. There were five successful pregnancies with nearly 100 oocytes treated in various ways. (Of necessity, all the lambs were female: in mammals, maleness is a kind of developmental afterthought.)

The underlying idea is that if the nuclei of cells of embryonic tissues growing in culture vessels are able to function as the cell nuclei of natural embryos, it will be possible to manipulate the genes of one of them in advantageous ways and return them to the uterus of recipient sheep. With luck, the result would be several improved sheep in a single season. In all the hype the other aim of this programme-the manipulation of genes-is hardly mentioned. That is not surprising. Biotechnologists have become skilled at replacing one gene with another in simple organisms such as bacteria, but this is not yet possible with mammalian chromosomes. Attempts to enable pigs to grow faster by giving them extra copies of a growth hormone gene have succeeded in giving them diabetes instead, presumably because the gene has been incorporated in the wrong places. The engineering of improved livestock will not be confident until that difficulty has been overcome.

But what about people? That is what the hype has been about. Experiments such as those carried out at the Roslin Institute would have to be licensed before they could be carried out with human germ cells. Given the general understanding that the time is not ripe for interfering with the human germ line, the application for a licence would have been turned down.

But, say the Brave New World worriers, it will not always be so. The special feature of the cells derived from sheep embryonic tissues is that they appear not to have been compromised by a commitment to a particular line of future development, so that they are able to function as true embryos-the fountain head of all mammalian attributes. And since every cell of the human body (except the red blood cell) has a complete human complement of DNA, it is just a matter of time before someone finds a way of unlocking that DNA and making an intact embryo from it.

Maybe, maybe not. At present there are only sketchy ideas of why a liver cell differs so markedly from a skin cell, for example. Maybe in each case the unwanted genes are not simply inactive, but permanently disabled. A dozen years from now, it will be easier to tell whether cloning a person from a single body cell will be feasible. The chances are that it will not be.

There is a stronger reason for believing that the Brave New World brigade is fighting this battle too soon. Even if body cells prove to be capable of generating fake embryos, so that the president of Iraq might think of having another like himself grown from a scraping of his skin, how could he be sure that the newcomer would think like him, not simply look like him? The new genetics has not banished the old argument about nature and nurture. One of the oddest features of this fuss is that liberal people, normally (and rightly) sceptical about genetic determinism, have been assuming that the die is cast the other way.