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.
He 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.
“I was kind of drawn to him for the first five or six minutes, he seemed very candid,” says Hank Greely, a professor of law at Stanford University and expert in medical ethics, who watched the conference live over the internet in November 2018. “And then as he went on, I got more and more suspicious.”
A genetic invention
In the years since, it’s become clear that He’s project was not quite as innocent as it might sound. He had broken laws, forged documents, misled the babies’ parents about any risks and failed to do adequate safety testing. The whole endeavour left many experts aghast – it was described as “monstrous“, “amateurish” and “profoundly disturbing” – and the culprit is now in prison.
However, arguably the biggest twist were the mistakes. 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 could 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 inadvertently 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.
More recently, researchers at the Francis Crick Institute in London warned that editing the genetics of human embryos can lead to unintended consequences. By analysing data from previous experiments, they found that approximately 16% had accidental mutations that would not have been picked up via standard tests.
Why are these mistakes so common? Can they be overcome? And how could they affect future generations?