What next?

After a rhesus monkey, will a human be far behind? Long before scientists took the nucleus from an adult sheep's cell to produce a sheep called Dolly, there have been debates about the ethical limits of cloning. For many, it seemed inevitable that after sheep and cattle, it would not take long before scientists started cloning humans. As early as 1993, Dr. Jerry Hall had announced that he had cloned human embryos by splitting them, although he said he had destroyed the clones.

This week the journal Science disclosed that US researchers have cloned a rhesus macaque. Unlike Dolly, Tetra the monkey was cloned from one-fourth of an embryo -- a method used to clone cattle, according to scientists at the Oregon Regional Primate Research Center. Many accounts of this major breakthrough carefully skirted the ethical debates and instead emphasized its benefits to medical research.

Scientists intend to study the effects of different maternal environments and other external factors on cloned monkey embryos. An embryo can also be split so that one is allowed to develop into an adult monkey while another is frozen for future harvesting of stem cells. Scientists believe stem cells can be used to grow new cells needed by the body for the treatment of incurable ailments such as Parkinson's disease.

We're still talking here of monkeys. But these primates are just an evolutionary hairbreadth away from humans. In the wake of an outcry from religious groups and ethicists, several governments have withheld official support for research in human cloning. But there is also a growing clamor for the development of cloned human embryos as a source of stem cells that can save millions of lives. The experiments on Tetra and other monkeys that are expected to be cloned in the future will prove how useful such embryos can be. And if stem cells can save the lives of monkeys, surely human stem cells from cloned human embryos can save human lives.

Will it be easier then to drown out opposition to human cloning? Do people have the right to play God? Or do people have the moral duty to do everything possible to save lives? Where does one draw the line? There are no easy answers to these questions. The birth of Tetra is an unsettling development at the start of the millennium.