Human cloning would be inconceivable and sick in the foreseeable future, the scientist whose pioneering work cloned Dolly the sheep said last night.
However, Prof Ian Wilmut said he was in favour of using cells from week-old embryos to treat diseases such as diabetes or arthritis, for which there is no fully effective treatment.
He was speaking at the spring Science Today lecture in Dublin, sponsored by The Irish Times and the Royal Dublin Society (RDS). His team at the Roslin Institute outside Edinburgh made history in 1996 when Dolly, the first mammal to have been cloned with adult cells, was born.
About 20 demonstrators from Compassion in World Farming and the Irish Anti-Vivisection Society protested outside the RDS in Ballsbridge. Their placards were in the shape of animals' heads, with half a pig's face painted on one side and half a sheep's or cow's face on the other.
Dr Wilmut told his audience of more than 500 that timing, hard work and good fortune played a significant part in the success of the Dolly experiment.
He said the institute team's technique could be used to make copies of sheep, cattle and goats, but not, to date, pigs, primates, rats or rabbits. The team is working on cloning a pig, and expects it to be successful this year.
Prof Wilmut said the Dolly technology was very inefficient, and resulted in the loss of about half of the foetuses produced and a fifth of the lambs born - between four to 10 times higher than in normally mated flock, he said.
Dolly resulted from the 277th cloning attempt using mature cells. She has given birth to three litters of healthy lambs.
Given the high death rate in cloning Dolly, which he predicted could be even higher in humans, he said: "Surely it would be inconceivable that people who have thought about human cloning would think of doing it, with women suffering from late abortions and sudden deaths of children?"
He added: "You have to be sick to suggest it. Apart from any other ethical issues, that alone in my mind should stop it for the foreseeable future." Prof Wilmut queried the ethics of human cloning, even if it was safe, to treat fertility, bring back a lost relative or copy a desired person.
He said people had phoned inquiring about the possibility of cloning their recently deceased children, including a two-year-old and two teenage girls who died in a car crash.
Prof Wilmut said a variety of factors influenced personalities, such as school friends, teachers or movies. "This chapter of events would be different for the copy. What sort of tension would there be if, instead of playing the flute, she played hockey?
"My fear is that these expectations would exist for a very long time and impose unreasonable expectations on the copy." In the interests of the child's welfare, such cloning would be unacceptable, he said.
Following his lecture Prof Wilmut took questions from the audience and signed copies of The Second Creation: The Age of Bio- logical Control, which he wrote with Dr Keith Campbell and a science writer, Mr Colin Tudge.