Scientists took conspiracy theories about SARS-CoV-2’s origins seriously, and debunked them.

The coronavirus pandemic circling the globe is caused by a natural virus, not one made in a lab, a new study says.

The virus’s genetic makeup reveals that SARS-CoV-2 isn’t a mishmash of known viruses, as might be expected if it were human-made. And it has unusual features that have only recently been identified in scaly anteaters called pangolins, evidence that the virus came from nature, Kristian Andersen and his colleagues report March 17 in Nature Medicine.

When Andersen, an infectious disease researcher at the Scripps Research Institute in La Jolla, Calif., first heard about the coronavirus causing an outbreak in China, he wondered where the virus came from. Initially, researchers thought the virus was being spread by repeated infections jumping from animals in a seafood market in Wuhan, China, into humans and then being passed person to person. Analysis from other researchers has since suggested that the virus probably jumped only once from an animal into a person and has been spread human to human since about mid-November .

But shortly after the virus’s genetic makeup was revealed in early January, rumors began bubbling up that maybe the virus was engineered in a lab and either intentionally or accidentally released.

Andersen assembled a team of evolutionary biologists and virologists, including Garry, from several countries to analyze the virus for clues that it could have been human-made, or grown in and accidentally released from a lab.

It was clear “almost overnight” that the virus wasn’t human-made, Andersen says. Anyone hoping to create a virus would need to work with already known viruses and engineer them to have desired properties.

But the SARS-CoV-2 virus has components that differ from those of previously known viruses, so they had to come from an unknown virus or viruses in nature. “Genetic data irrefutably show that SARS-Cov-2 is not derived from any previously used virus backbone,” Andersen and colleagues write in the study.

“This is not a virus somebody would have conceived of and cobbled together. It has too many distinct features, some of which are counterintuitive,” Garry says. “You wouldn’t do this if you were trying to make a more deadly virus.”