A US company claims to have successfully cloned a human embryo for the first time, opening a hugely controversial new chapter in the debate about the ethics of genetic engineering.
Advanced Cell Technologies (ACT), of Massachusetts, insists that it has not created, and does not intend to create, human life. Instead the technology is to be used as a means of harvesting "stem cells" which in turn can be used to treat many genetic diseases such as Parkinson's and diabetes.
Acknowledgement that an embryo has been cloned, no matter what the purpose, will cause considerable disquiet among the public and raise powerful ethical issues. Having proved human cloning as a technique, it will only be a matter of time before some rogue group attempts to clone for reproductive purposes. Stem cells are hugely valuable because they can be persuaded to grow into any cell type in the human body. These cells could be used to replace the damaged or degraded cells that are responsible for many diseases.
The use of stem cells from aborted embryos or those surplus to requirements in the in-vitro fertilisation process has recently been enormously controversial in the US.
The government had considered withdrawing federal research support for this work, and many scientists pleaded against such a decision.
President Bush eventually compromised by allowing continued state support for research that involved only existing stem cell lines.
Congress has continued to discuss a total ban on human cloning. This proposal has been backed by the House, but is still being debated in the Senate.
Politicians responded warily to yesterday's announcement, which is likely to face close scrutiny. Yet, reporting on their new work in Scientific American, the ACT team, doctors Jose Cibelli, Robert Lanza, Carol Ezzell, and Michael West described their new technique as potentially representing "the dawn of a new age in medicine by demonstrating that the goal of therapeutic cloning is within reach".
Dr West admits the technique may be used in cloning human beings. He insists, however, that reproductive cloning through the implantation of the cloned embryos in a woman's uterus is qualitatively different from his work.
"Scientifically, biologically, the entities we are creating are not individuals. They're only cellular life. They're not human life," he said.
For Catholic and conservative Protestant groups any embryo represents a potential viable life, and tinkering with them to produce stem cells is akin to abortion even if the result is valuable new therapies.