South Korean scientists based at the Seoul National University stirred up a storm worldwide last week when they announced in the online edition of the journal Science that theyhad derived a line of pluripotent embryo stem cells from one of 30 cloned blastocysts created by somatic cell nuclear transfer. In other words, they had created the first human cloned embryos (www.sciencemag.org/cgi/content/abstract/1094515).

Until last week, the consensus among cloning scientists had been that humans—and other primates—might prove much more difficult to clone than mice or sheep.

The team was …