A scientist has achieved a world first... by cloning himself.
In a breakthrough certain to provoke an ethical furore, Samuel Wood created embryo copies of himself by placing his skin cells in a woman's egg.
The embryos were the first to be made from cells taken from adult humans.
Although they survived for only five days and were smaller than a pinhead, they are seen as a milestone in the quest for treatments for diseases such as Alzheimer's and Parkinson's.
But critics fear the technology could be exploited by mavericks to clone babies and accused the scientists of reducing the miracle of human life to a factory of spare parts.
Researchers from the Californian stem cell research company Stemagen employed the same technique used to make Dolly the sheep, the world's first cloned mammal, to create the embryos.
They took eggs donated by young women having IVF and replaced genetic material with DNA from the skin cells of two men.
The eggs were then zapped with an electric current to induce fertilisation and the creation of embryos.
Some of the skin cells came from Dr Wood, Stemagen's chief executive officer and a leading fertility specialist, while the others came from another member of staff.
The result was a handful of embryos, at least three of them clones of Dr Wood and the other man.
Although all were destroyed in the process, the technique is seen as a vital step in the creation of cloned embryos rich in stem cells, which are "master cells" capable of becoming any type of body tissue.
Such stem cells could be invaluable in the study of diseases and the testing of drugs.
They could ultimately be used to replace the damaged tissues behind diseases from Alzheimer's to diabetes.
Stem cells taken from cloned embryos would be a perfect match to the patient, whose body would not reject them.
Dr Wood, who has degrees in medicine, psychology, biochemistry and molecular biophysics, called the research "a critical milestone" in the development of treatments.
The unmarried father of two, who is in his forties, is working on extracting stem cells from such embryos - a process that inevitably leads to the death of the embryo.
John Smeaton, of the Society for the Protection of Unborn Children, said: "We have got scientists wandering around in an ethical wilderness, forgetting about matters of justice relating to our fellow human beings.
"We have people creating human beings with the intention of destroying them. That's appalling."
And the Vatican condemned the cloning of human embryos, calling it the "worst type of exploitation of the human being".
"This ranks among the most morally illicit acts, ethically speaking," said Monsignor Elio Sgreccia, president of the Pontifical Academy for Life, the Vatican department that helps oversee the Church's position on bioethics issues.
Stem cell experts gave the U.S. breakthrough, published in the journal Stem Cells, a cautious welcome.
Professor Robin Lovell-Badge, of the Medical Research Council's National Institute for Medical Research, said: "This is another step along what has turned out to be a tortuous road.
"However, it is still a long way from the goal of achieving embryonic stem cells."
U.S. researcher Professor Robert Lanza questioned the validity of the research and said the embryos looked "very unhealthy".
Josephine Quintavalle, of the campaign group Comment On Reproductive Ethics, said: "Human cloning is unethical, unsafe, and completely unnecessary.
"It is time that scientists started to put some brakes on."
Dr Calum MacKellar, of the Scottish Council on Human Bioethics, said the creation and destruction of human embryos was "extremely offensive to millions in the UK".
Although Dr Wood's team is the first to create human embryos from adult cells, human embryos have been cloned before.
Scientists at Newcastle University created cloned human embryos in 2005 using cells from embryos rather than adults, seen as less useful in creating potential treatments.
British law says created embryos must be destroyed in 14 days and cannot be implanted in a woman.
The news came as it was revealed that animal-human hybrid embryos will be created in British laboratories within weeks after the research was allowed by the Human Fertilisation and Embryology Authority.
Two teams have been licensed to make cow-human hybrids for research into incurable diseases.
Scientists say they are needed because of a shortage of human eggs for research.
The embryos would be more than 99 per cent human and would have to be destroyed after two weeks.
But Mr Smeaton said: "It is creating a category of beings regarded as sub-human who can be used as raw material to benefit other members of the human family.
"How wrong can something be before a scientist understands you cannot just do it because of the perceived good for human beings."
