Scientists produce embryo clones of 2 men, using skin cells in step toward stem cell goal

Scientists in California say they have produced embryos that are clones of two men, a potential step toward developing scientifically valuable stem cells.

The new report documents embryos made with ordinary skin cells. But it is not the first time human cloned embryos have been made. In 2005, for example, scientists in Britain reported using embryonic stem cells to produce a cloned embryo. It matured enough to produce stem cells, but none were extracted.

Stem cells were not produced by the new embryos either, and because of that, experts reacted coolly to the research.

"I found it difficult to determine what was substantially new," said …