In an article in the US journal Science, Dr Wilmut denounced the declared aim of the Italian and US fertility specialists Severino Antinori and Panos Zavos to clone humans and enable infertile men to pass on their genes. In language a world away from the optimism in 1997 at the birth of Dolly, Dr Wilmut warned that four years of experiments on animals had shown the cloning technique to be deeply flawed, exacting a huge toll of miscarriages and deformities. The polemic, written jointly with a US biologist, was timed for hearings in the US House of Representatives on human cloning. Since Dolly, scientists have cloned mice, cattle, goats and pigs. Dr Wilmut and Dr Jaenisch point out that very few cloned embryos survive to birth and many of these die shortly after.
Survivors are often grotesquely large or have defects.
Dr Wilmut is sceptical of the Zavos-Antinori claim that decades of IVF work helping infertile couples enable them to screen cloned human embryos for defects before they are implanted in the womb. A normal child has a 50-50 mix of its father's and mother's genes, prepared for their embryonic role in eggs and sperm over months and years. In cloning, the genes are almost entirely from one parent and their calibration is done in minutes. No IVF clinic has the capability to screen all an embryo's genes for problems, said Dr Wilmut. He told the Guardian yesterday of a cloned lamb born in December at his institute in Roslin near Edinburgh.