Here’s why: SARS-CoV-2 is very closely related to the virus that causes severe acute respiratory syndrome (SARS), which fanned across the globe nearly 20 years ago. Scientists have studied how SARS-CoV differs from SARS-CoV-2 — with several key letter changes in the genetic code. Yet in computer simulations, the mutations in SARS-CoV-2 don’t seem to work very well at helping the virus bind to human cells. If scientists had deliberately engineered this virus, they wouldn’t have chosen mutation…