While human enhancement has little mainstream scientific support, gene-editing to eliminate diseases from human populations is a vision many share. Now, following breakthrough technologies and the shocking case of He Jiankui editing the germ-line of two human girls, the editing of heritable human cells has appeared on the horizon whether we like it or not. What will the dream of human gene editing deliver? Sahotra Sarka, author of 'Cut-and-Paste Genetics', weighs up the credibility and safety of the new science of the CRISPR revolution.

In Hong Kong in November 2018, immediately before the start of the International Summit on Human Genome Editing, Chinese biologist He Jiankui stunned the world by announcing that he had successfully edited the germ-line of two little girls born earlier in the month. The girls were daughters of HIV-positive fathers, and He had used CRISPR-based techniques to edit their CCR5 gene, the typical version of which was believed to enhance susceptibility to HIV infection. These CRISPR-based techniques, first introduced in 2012, are the simplest, cheapest, most accurate, and most flexible methods that have ever been developed to edit genes, whether they be in ordinary (somatic) cells or the reproductive (germ-line) cells of any organism including humans. CRISPR-based gene editing is so simple that it can be done in a basement or garage. DIY kits cost less than US$ 200 and can be bought online. [1] 

As far as is publicly known, He Jiankui was the first person to carry out human germ-line editing and bring the embryos to full term. He had carried out his project openly, discussing his plans with colleagues including his former PhD advisor, Michael Deem of Rice University as well as prominent Stanford bioethicist, William Hurlbut. These colleagues would later claim that they had tried to dissuade He but there is little evidence that suggests that they tried very hard.