Assessing the theory that covid-19 leaked from a Chinese lab

IT IS POSSIBLE that the chain of infections which spread SARS-CoV-2 around the world began, as most new diseases do, when an animal virus found its way unaided into humans, whether in field or farm, cave or market. It is also possible that the chain began in a Chinese government laboratory. These two possibilities have been recognised by many of those studying the covid-19 pandemic for a long time. But the fact that two things are both possible does not mean they are equally likely.