That said, circumstantial evidence casts some doubt on the claim that SARS-CoV-2 was bioengineered. For instance, aspects of the virus that have made some suspect it was bioengineered could also be evidence that the virus evolved naturally. A lot of attention has been drawn to an unusual feature on its spike protein called a furin cleavage site, with which the virus can better infect a human cell. It’s one of several odd features of SARS-CoV-2 that are weird enough that even virologists who greatly doubt lab involvement told me they were shocked to see it. In fact, even beyond the furin cleavage site, SARS-CoV-2 was a virus that scientists had never seen before. Evolution can be a random accumulation of weird, novel features. For the research on viruses that scientists like Dr. Shi do for high-level scientific publications, such a combination would be incongruous. Their work usually involves examining or changing one element of a virus at a time to find out what each element does and can be made to do. If your computer conked out, for instance, you wouldn’t see what’s wrong by simultaneously changing the power source, the cable and the electrical outlet. You’d test each one individually. Having a variety of unusual elements leads to hard-to-assess results, not a paper in Nature. But even if we put aside directed engineering, regular lab work at the Wuhan labs has raised concerns.