More cloning news closed out 1998.

The efficient cloning of a cow in Japan and a deliberately aborted cloning of a woman in South Korea have continued to fan the furor over this new reproductive strategy.

Although several research groups had already created clones of adult mammals--sheep, cows, and mice--the success rates haven't been much to brag about. Few of the embryos generated actually survive and develop into healthy adults.

In the Dec. 11, 1998 SCIENCE, however, Yukio Tsunoda of Kinki University in Nara, Japan, and his colleagues report the birth of eight calves through the cloning of cells from an adult cow. These calves were the result of just 10 implanted embryos, a remarkable success rate that gives researchers hope that cloning can be an efficient way to generate animals with desired traits. For example, Tsunoda's group and several others in his country are looking to create clones of cows that are especially valued in Japan for the taste of their meat. Four of Tsunoda's eight calves died soon after birth, although it's unclear whether the deaths were due to the cloning or unrelated problems.

Such uncertainty about the health of cloned animals is one reason why many scientists reject the idea that human cloning will occur soon. Last month, however, researchers at the Kyunghee University Hospital in South Korea announced a small step toward that goal. They had taken the DNA-containing nucleus from a cell of an infertile woman and transplanted it into one of her eggs, which had previously been surgically harvested and had its own DNA removed. The egg divided twice before the researchers destroyed it, in accord with South Korea's laws on experimenting on human embryos.

The experiment was disclosed at a press conference, not in a peer-reviewed journal. Some cloning researchers argue that the work does not offer any information on the feasibility of human cloning. Although the woman's egg started dividing, a developing embryo doesn't actually use its DNA until the fourth or fifth round of cell division. The South Korean experiment, therefore, ended before researchers could evaluate whether the DNA transfer was a success, critics say.