The world was shocked in 2018 when He Jiankui, a Chinese biophysicist, announced that he had helped to produce two girls whose genetic code he had edited when they had been embryos. His aim had been to tweak a gene that sometimes confers protection against HIV infections. No one had ever used the CRISPR gene-editing tool in reproduction before and it was completely untested in embryos. Scientists around the world condemned the work as wildly premature and possibly dangerous—the Chinese authorities agreed and Dr He was imprisoned for three years. Now, more than six years later, Dr He is back. And he still wants to prevent medical conditions by editing human embryos. But will the world ever be ready for this use of gene editing? Or will newer methods of editing human genes prove more promising?

Host: Alok Jha, The Economist’s science and technology editor. Contributors: Emilie Steinmark, science correspondent at The Economist; Chinese researcher He Jiankui; Henry (Hank) Greely of the Stanford Centre for Biomedical Ethics; Panicos Shangaris of King's College Hospital.

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