germline editing ethics

There is a sharp ethical line in genome editing that depends entirely on which cells you edit. Editing the cells of a sick patient — their blood or liver cells, say — affects only that one person and dies with them; this is called somatic editing and is, broadly, treated like other medical treatments. Editing an egg, a sperm, or an early embryo is utterly different: the change will be present in every cell of the resulting person and, crucially, will be passed down to all their descendants. This is germline (heritable) editing, and it is where the gravest questions live.

Why so serious? An edit made in an embryo is permanent for the human family tree, performed on a person who could never consent, with consequences that ripple into future generations we cannot consult. The risks are real and partly unknown: off-target edits, mosaicism (where only some of the embryo's cells get edited, so the resulting person is a patchwork), and unforeseen effects of altering a gene whose full role we may not understand. And the slope toward editing not to prevent disease but to select traits — so-called designer babies — raises deep questions of fairness, consent, disability, and what we owe to people not yet born.

This is not abstract. In 2018 a Chinese scientist, He Jiankui, announced he had used CRISPR to edit the genomes of twin girls as embryos, aiming to make them resistant to HIV. The work was widely condemned by the scientific community as premature, medically unjustified, secretive, and a violation of ethical and safety norms; he was later convicted and imprisoned. The episode crystallised a broad international consensus: heritable human genome editing should not be used clinically at present, both because it is not safe enough and because society has not resolved whether and how it should ever be permitted. The science raced ahead of the ethics, and the He Jiankui case is the cautionary line everyone now points to.