He Jiankui presents the results of his experiment to create gene-edited babies at the Second International Summit on Human Genome Editing in Hong Kong last week.

The ‘CRISPR babies’ experiment was more flawed than scientists first realized

When He Jiankui unveiled data last week on the two baby girls born from embryos whose genes he had edited with CRISPR-Cas9 — the world’s first “CRISPR babies” — his 59 slides flew by in a 20-minute blur, leaving scientists in the audience of the International Summit on Human Genome Editing desperately taking iPhone pictures for later scrutiny.

Now many of them, as well as researchers who watched the webcast of the Hong Kong summit, have had time to analyze the data. The verdict: What He did is way worse than initially realized.