Zaria Gorvett in BBC:
He Jiankui seemed nervous. At the time, he was an obscure researcher working at the Southern University of Science and Technology in Shenzhen, China. But he had been working on a top-secret project for the last two years – and he was about to take to the podium at the International Summit on Human Genome Editing to announce the results. There was a general buzz of excitement in the air. The audience looked on anxiously. People started filming on their phones. Jiankui had made the first genetically modified babies in the history of humankind. After 3.7 billion years of continuous, undisturbed evolution by natural selection, a life form had taken its innate biology into its own hands. The result was twin baby girls who were born with altered copies of a gene known as CCR5, which the scientist hoped would make them immune to HIV.
But things were not as they seemed.
…It turns out that the babies involved, Lulu and Nana, have not been gifted with neatly edited genes after all. Not only are they not necessarily immune to HIV, they have been accidentally endowed with versions of CCR5 that are entirely made up – they likely do not exist in any other human genome on the planet. And yet, such changes are heritable – they might be passed on to their children, and children’s children, and so on. In fact, there have been no shortage of surprises in the field. From the rabbits altered to be leaner that inexplicably ended up with much longer tongues to the cattle tweaked to lack horns that were unintentionally endowed with a long stretch of bacterial DNA in their genomes (including some genes that confer antibiotic resistance, no less) – its past is riddled with errors and misunderstandings.