Scientists at a small biotech company in California say they have cloned five human embryos from the cells of in a technological feat they claim will one day provide a source of viable embryonic stem cells. Cloned human embryos have been created from a male adult's skin cells for the first time using the same approach that led to the birth of Dolly the cloned sheep.



The five embryos did not develop beyond an early stage and the scientists were unable to extract embryonic stem cells from the clones, which would have been critical for research into many serious human diseases. It is not the first time that scientists have created cloned human embryos - British scientists claim to have cloned a human embryo two years ago, proving that humans can be replicated in the laboratory just as scientists have been able to clone a host of animals - but it is the first time that it has been done by fusing a woman's unfertilised egg with the genetic material of an adult man's skin cells. 

The coveted primordial cells that scientists theorize may one day be used to treat a range of human afflictions were not generated in the experiment. And the five clones, created in the laboratories of Stemagen Corp. were destroyed.

Dr. Samuel Wood, a medical doctor and chief executive of the company, along with a colleague, donated skin cells to begin the process of making human clones. DNA from those cells was transferred to human eggs. Creating human clones is not considered groundbreaking. But the next step, which could have been a landmark  - generating viable stem cells from human clones - did not occur.

The team at Stemagen Corporation in La Jolla, California, says the work could be an important stage in developing embryonic stem cells for patients. Many scientists believe that being able to make stem cell lines tailored to individual patients could revolutionise the treatment and prevention of human diseases.

But the research has proved controversial. Korean scientist Hwang Woo-suk claimed in 2005 that he had created such cell lines, but the study was later discredited. Meanwhile, critics have objected on ethical grounds, saying it is wrong to use embryos for research.

Some scientists argue that clones might not be required to harvest stem cells. Last year, researchers in Japan and the US were able to "rewind" adult cells back to their embryonic state using a new technique.