If anyone had devised a way to create a genetically engineered baby, I figured George Church would know about it.
At his labyrinthine laboratory on the Harvard Medical School campus, you can find researchers giving E. Coli a novel genetic code never seen in nature. Around another bend, others are carrying out a plan to use DNA engineering to resurrect the woolly mammoth. His lab, Church likes to say, is the center of a new technological genesis—one in which man rebuilds creation to suit himself.
When I visited the lab last June, Church proposed that I speak to a young postdoctoral scientist named Luhan Yang, a Harvard recruit from Beijing who’d been a key player in developing a new, powerful technology for editing DNA called CRISPR-Cas9. With Church, Yang had founded a small company to engineer the genomes of pigs and cattle, sliding in beneficial genes and editing away bad ones.
As I listened to Yang, I waited for a chance to ask my real questions: Can any of this be done to human beings? Can we improve...