Editor’s letter

The stuff of science fiction is once again becoming the stuff of reality. In a breakthrough study, researchers in the U.S. and China have created for the first time embryos that contain both human and monkey cells (see Health & Science, p.21). Scientists hope that these mixed-species “chimeras”—named for the fire-breathing creature of Greek mythology that’s part lion, part goat, and part snake—will help them find new ways to grow human organs for transplant and provide better subjects in which to test drugs and study disease. “Our goal is not to generate any new organism, any monster,” study co-author Juan Carlos Izpisua Belmonte told NPR .org. The embryos were destroyed after 20 days, but bioethicists worry that someone will push this work further and try to produce a chimeric baby. Human cells might end up a part of the resulting creature’s brain, raising questions about whether the hybrid would be classed as human, animal, or something else entirely. “I don’t think we’re on the edge of Planet of the Apes,” said Stanford

University bioethicist Hank Greely. But it’s “time for us to start thinking about ‘Should we ever let these go beyond a petri dish?’”

History suggests that these clusters of cells won’t remain in the dish for long. In the early days of artificial intelligence, researchers insisted that thinking machines would be used only for good and that the killer robots of The Terminator were dystopian nonsense. Yet Russia, China, and the U.S. are all developing AI weapons that can identify and “engage”—that is, kill—human targets. And for years it was the consensus of the scientific community that gene-editing tools should not be used to create so-called designer babies. Then a rogue Chinese researcher, He Jiankui, did just that. In 2019, he announced the birth of twin girls whose genomes he’d secretly—and poorly—edited with the aim of making them immune to HIV. The chimeras are coming, because whatever science can do, it inevitably will do. Theunis Bates

Managing editor