And that has yet to happen, warned Ian Wilmut of Scotland's Roslin Institute, which gained fame five years ago with the birth of Dolly the sheep, the first clone of an adult mammal, New Scientist reported Friday.
Wilmut proposes a far-ranging research agenda that will provide the needed insight that will legitimize commercial human cloning, Wilmut said.
The promise of cloning human cells is immense, Wilmut said, especially for growing organs that can be transplanted without fear of rejection. But the risk is even greater -- the few cells that survive cloning often suffer life-threatening abnormalities.
"There are a lot of questions to ask about cloned cells before you can justify putting them in a patient," said Wilmut.
Wilmut says commercial cloners need to systematically study every aspect of the cloning process, its genetic and physiological effects on embryo, placenta, fetus and live animal.
In his plan, clones would be compared side by side to natural embryos and test-tube fertilized embryos.