That was the second scenario: natural selection acting on the virus, within its animal host, before spillover into humans. The pangolin coronavirus was important evidence here, demonstrating that an RBD almost identical to the RBD in SARS-CoV-2 could evolve—because it had evolved—in a wild animal. And of course the cross-border trade in live pangolins for meat and medicine, with thousands of the animals passing from trader to buyer to butcher to consumer, provided plenty of opportunities for a pangolin virus to spill into some person.
