More than a year and a half into a global pandemic that has caused at least four million deaths, the world is still debating two competing hypotheses about the origins of the novel coronavirus that causes COVID-19. The first hypothesis—and until recently the dominant one—is that the virus jumped from animals to humans in a natural “spillover” event. Animal-to-human transmission has happened repeatedly throughout history. And although no animal has been identified as the culprit in this pandemic, there is evidence that species sold in Wuhan’s wet markets could have caught the novel coronavirus from a bat and then spread it to humans.
The second hypothesis, which was initially dismissed as a conspiracy theory but has gained traction in the wake of recent news reports, is that the novel coronavirus escaped via an accidental lab leak. The earliest reported cases of COVID-19 occurred in Wuhan, which is home to the Wuhan Institute of Virology, China’s highest-security lab for biohazards and an institute renowned for coronavirus research. Wuhan is also a bustling metropolis of more than ten million people—not a natural habitat for the bat colonies where coronaviruses are typically found.
Both hypotheses are plausible, but