Human Embryo Gene Editing Gets a Road Map—Not a Green Light

FOR DECADES, SCIENTISTS have been tinkering with genes—cutting and pasting bits of DNA into organisms like plants, bacteria, and mice. So, of course, they thought about the possibility that one day someone might use such tools to alter human genes, even human germlines—making changes to people’s DNA that they’d pass on to future generations.

In 2012 these dreams (or nightmares, depending on where you stand) started to get real. With the emergence of Crispr, genetic manipulations were suddenly much easier to make and the tools to make them quick and cheap to obtain. The National Academy of Sciences arranged summits and reports in an attempt to set some boundaries. In 2017 the academy concluded that using Crispr for human genetic enhancement was a hard no. But they stopped short of a full moratorium. What about gene editing to address serious, incurable diseases? Well, that could maybe one day be fine, provided it was proven safe and effective.

But that 2017 report didn’t spell out exactly how one might prove those things. And a year later, into that...