A Chinese scientist claims to have ushered in the age of genetic enhancement this week, with the announcement that he had tweaked the DNA of two human embryos, now twin girls, endowing at least one of them with resistance to HIV. This kind of thing has always ended badly in movies, but like any advance in medical technology, it could help people and it could do harm.
If the claim is true, this is new territory on two fronts. It would be the first time scientists have changed the human germline — the genes that could be passed down for centuries to come. And beyond that, it would be the first time that genetic engineering of any kind has been used for human enhancement rather than to correct a genetic disorder.
