An analysis of Hwang's work published Thursday in the monthly Cell Stem Cell by Kitai Kim and George Daley of the Children's Hospital Boston Stem Cell Program, shows that the stem cells Hwang obtained contained genetic material only from the donor egg and had not been cloned from a human embryo.
Hwang and his team "unwittingly created something entirely different - the world's first human embryonic stem cell to be derived by parthenogenesis," the two US researchers said in a press release.
"We now know that the Korean's first supposed nuclear transfer-derived stem cell line was actually derived from the woman's egg alone," said Daley.
Parthenogenesis is a method of reproduction, common in plants and in some reptiles, in which the female can generate offspring without the contribution of the male, through artificial activation of unfertilized eggs.
Parthenogenesis in mammals is seemingly very difficult.
In cloning, the nucleus of an egg is replaced with the nucleus from a cell in a different body to produce, theoretically, genetically identical embryonic stem cells. That is what Hwang claimed he did in 2004.
A year later however Hwang confessed that his entire body of research on stem cells, which was published in the journal Science, had been faked.