Almost two years into the COVID-19 pandemic, the origin of the virus tormenting the world remains shrouded in mystery. Most scientists believe it emerged in the wild and jumped from bats to humans, either directly or through another animal. Others theorize it escaped from a Chinese lab. Now, with the global COVID-19 death toll surpassing 5.2 million on the second anniversary of the earliest human cases, a growing chorus of scientists is trying to keep the focus on what they regard as the more plausible “zoonotic,” or animal-to-human, theory, in the hope that what's learned will help humankind fend off...