“If you make a living entity without a brain at all, I think we’d be pretty comfortable with thinking it can’t feel pain,” says Hank Greely, a bioethicist at Stanford University, who has written about the potential for human “bodyoids” that lack sentience. “It’s highly possible that none of this will ever work, but it’s also possible that it could.”

Greely thinks it will be important to get buy-in from the public, since the concept is so unsettling. “I think the ‘yuck factor’ will be strong,” he says, “but that depends in part on what any resulting things look like and how they behave.”