Designing babies

One of the greatest scandals in modern science began with a late-2010s advertisement for HIV-positive couples looking to have children through in-vitro fertilisation (IVF). The ad had been put out by a scientist named He Jiankui, a biologist then at the Southern University of Science and Technology in China. Several pairs responded. For each couple, Dr. He and his team harvested their sperm and eggs and created embryos through IVF. He edited a gene in each embryo using CRISPR, then did something that had never been done before: had the edited embryos implanted into the women’s wombs. The gene, CCR5, is responsible for a cell-surface protein which plays a key role in HIV infection. A natural variant of CCR5 blocks production of the protein and confers protection against HIV. It was this protection that Dr. He sought to give the embryos.

In November 2018, just before the second International Summit on Human Genome Editing, MIT Technology Review reported both that the experiments had taken place and that two of the embryos had, when implanted in the womb, resulted in successful...