Ian Wilmut was happy to clone Dolly the sheep but he is appalled by the prospect of cloning humans. Justine Burley reports on his Amnesty lecture

Ian Wilmut, whose team at the Roslin Institute in Edinburgh last year produced the world's first cloned mammal, Dolly the sheep, has already been approached by a bereaved mother asking whether her dead child could be cloned.

Giving the second in a series of seven Amnesty lectures on genetics in Oxford last week, Wilmut, principal investigator at the institute, revealed he had recently had a painful telephone conversation with a grieving mother. Her request about the possibility of cloning her dead child did not change his view that cloning individual humans is "quite simply dangerous". It is not the first such conversation he has had; his office has had to field several phone calls from people who have lost relatives and who clutch at the hope that cloning may be the solution. Wilmut tells them all the same thing: that at present, "the technique is associated with a high rate of post-natal mortality, foetal loss and foetal abnormality".

Although Wilmut acknowledged that, over time, many of these problems will be overcome, he still has grave reservations about the risks associated with the cloning of humans. In his lecture, "Dolly: the Age of Biological Control", he dismissed as "appalling" the American scientist Richard Seed's widely reported intention to establish a cloning clinic for infertile couples. Arguments defending cloning ignore how a cloned child will feel, says Wilmut. Copying chromosomal DNA (that part of our genetic complement that determines our appearance) could involve grave psychological costs to any cloned child, who would inevitably look exactly like one of his or her parents. Cloning could severely damage family relationships, he warned.

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Moreover, we do not know as yet what effect cloning an adult has on the ageing process. One of the things the Roslin team is monitoring the now pregnant Dolly for (she was cloned using a cell taken from the udder of a six-year-old ewe) is whether she will grow old more quickly than her natural counterparts (see box).

But even if he is wary of cloning humans, Wilmut does think there are enormous potential benefits to nuclear transfer, the technique used to clone Dolly. Nuclear transfer could be used, for example, to manufacture individualised cells for the treatment of illnesses like Parkinson's disease, muscular dystrophy, leukaemia and diabetes. From a Parkinson patient's nerve cells, for example, it might be possible to culture stem cells which could then be prompted to develop into a completely different kind of cell. If injected into the brain of someone with Parkinson's these stem cells might grow into healthy neural tissue and possibly reverse the disease. Scientists might also be able to remove defective cells from an embryo and substitute "healthy" ones to eradicate certain kinds of disabilities. Copying animals is certain to be useful in drug trials - in studying the responses of diseased animals to different drug treatments - and in producing high quality meat or milk with elements such as clotting factor 9, needed by haemophiliacs.

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Widespread fears about the new cloning technology have sparked massive debate about whether scientists should be allowed to develop the technology untrammelled. Particular worries have centred on whether dictators like Saddam Hussein would seek to use the technology to clone copies of themselves. Should new laws be enacted to try to control some of the possible directions scientists may wish to explore? Who should decide what are the limits of acceptable scientific enquiry?

Wilmut believes that society rather than scientists or drug companies (who stand to make a lot of money out of applications of the cloning technology) should decide where to draw the line. "Such choices should be made by society", he told the audience at Oxford's Sheldonian Theatre. Individual states should try to regulate scientific innovation according to the views of their citizens. But he also warned that one consequence of different states having different laws was likely to be a "brain-drain" of talented researchers to countries with the laxest legislation. Countries which sought to enforce strict bans might lose their best scientists, who would move to states where they were permitted to experiment relatively freely. Legislation might then be relaxed in a bid to entice the scientists back again.

In the absence of international legislative parity, limiting certain kinds of scientific investigation in individual countries will achieve very little. This is because market forces in a global economy have an extremely strong influence on the direction that research and development takes in any one country. If you want to introduce appropriate legislation to control the development of new technologies you have to enforce legislation internationally.

This, however, is easier said than done. There is too wide a range of views across nations about the moral acceptability of certain kinds of research. Any agreement reached internationally would probably be too restrictive on scientists, because it would have to be the result of a series of compromise agreements, reflecting the views even of those hostile to the bulk of nuclear transfer research.

In view of some of the statements issued by international bodies such as the World Health Organisation and Unesco over the past year, this argument is convincing. Terms like "human dignity" crop up with depressing regularity in proposals for legislation with little thought about the implications of outright bans on one small area of nuclear transfer research (cloning humans) for other research applications. In the short term, this is perhaps a necessary evil. But any policy, national or international, based on half the facts, or, for that matter, on careless usage of the language of rights and dignity, serves no one in the long run.

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Justine Burley is lecturer in politics at Exeter College, Oxford and research fellow at the Institute of Medicine, Law and Bioethics, University of Manchester. She is convenor of "The Genetic Revolution and Human Rights", this year's Amnesty lectures, which are sponsored by The THES.

Since the publicity over Dolly, Ian Wilmut has been approached by bereaved people asking him to clone lost relatives. Although he believes human cloning would be dangerous, he warns that researchers who are less fastidious could operate in countries where cloning laws are lax. He also denies reports that Dolly was not a true clone (see box)

WHAT KIND OF MIXTURE IS DOLLY?

Doubts over whether Dolly is indeed the first genuine clone of an adult mammal were answered by Ian Wilmut during his Amnesty lecture.

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Some have argued that, because other groups have failed to repeat the cloning experiment, there may be a possibility that the Dolly research was in some way, unwittingly, contaminated.

An independent investigation into Dolly's genetic heritage has now been requested by scientists at the Roslin Institute. It will be carried out by American researchers.

Although it is standard practice in science not to publish a paper before you have demonstrated that your experiment can be replicated, Wilmut says that, statistically, it is not surprising that the lab which did attempt to repeat the experiment has not done so. While Dolly was born of 400 attempts, the next clone may take 2,000 tries. He is absolutely certain that the experiment will be replicated soon.

Another criticism relates to the fact that because the cells used to clone Dolly were culled from a sheep which was pregnant it is possible that embryo stem cells were present in the cell cultures used to clone Dolly. In other words, it is claimed that Dolly may really be the product, not of a process which involved the use of specialised cells from an adult sheep's udder, but of an embryo stem cell.

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This is an extremely remote possibility and Wilmut says he is quite confident it is not the case.