Dolly, the world's most famous sheep, was cloned from the udder cells of an adult ewe. On announcing her birth in 1997, embryologists Ian Wilmut and Keith Campbell, who had engineered her, noted that she had been named in honor of the entertainer Dolly Parton. Wilmut explained, "No one could think of a more impressive set of mammary glands than Dolly Parton's." Parton responded, "I'm honored."

Dolly's birth was a milestone in the engineering of animals for food and medicine, but not everyone was as pleased as Parton by the event, much less by the implication that the same methods might be used to clone human beings. On the contrary: since Dolly's arrival, the prospect of human reproductive cloning has been widely condemned by clerics and ethicists, politicians, pundits and scientists as unethical, unsafe and socially dangerous.

Yet human cloning will almost surely happen. In the past, other new reproductive technologies were also denounced at first; but then they were adapted to serve human procreational needs and ultimately became commonplace practices. Human cloning already has advocates-according to polls, six to seven percent of adult Americans, including, no doubt, many who cannot or prefer not to have children by conventional means. If human cloning is made reliably safe for both mother and child, market demand for it will gain considerable force, likely overpowering the residue of moral objection.

At the moment, the moralists enjoy a strong advantage. Ian Wilmut himself opposes human cloning, calling it "offensive." Clerics of many different faiths attack it as a violation of God's order; ethicists denounce it as a denial of the cloned child's right to a unique genetic identity. Social critics warn that cloning would simply permit the rich to indulge in reproductive egomania or entrepreneurs to mass-produce superior athletes. In a recent report, a panel appointed by the National Academy of Sciences concluded, based on animal experiments conducted since 1997, that production of babies by cloning "is dangerous and likely to fail" and that human reproductive cloning should be legally prohibited. Laws banning it have been enacted in 24 countries, including France, Germany, the United Kingdom, India, Japan, South Africa and Brazil. Calls for the prohibition of human cloning have been strongly endorsed by President George W. Bush and the U.S. House of Representatives, though not-as Technology Review goes to press-by the Senate.