The team found the “close relative” virus, called RmYN02, among 227 bat samples collected in the southwestern Chinese province of Yunnan between May and October last year.

Like Sars-CoV-2, RmYN02 has amino acid insertions at the junction of its spike protein’s subunits.

These insertions, which are thought to increase Sars-CoV-2’s capacity to cause disease, were previously seen as highly unusual and even indicative of laboratory manipulation, according to one of the study’s authors.

“Our findings suggest that these insertion events, which initially appeared to be very unusual, can, in fact, occur naturally in animal betacoronaviruses,” Science Daily quoted Professor Shi Weifeng, director of the Institute of Pathogen Biology at Shandong First Medical University, as saying.

“This provides strong evidence against Sars-CoV-2 as having escaped from a laboratory.”

Despite both coronaviruses sharing similar “insertion” features, RmYN02 appears much less threatening to humans than Sars-CoV-2, which has sickened more than 4 million people around the world since it was first discovered in Wuhan in central China in December.

One of the big differences was that RmYN02 did not have a crucial part of the Sars-CoV-2 genome that helped bind the pandemic coronavirus to human cells.

The amino acids presented in the insertions were also different, and RmYN02, was not a direct ancestor of Sars-CoV-2, the researchers said.

“There is still an evolutionary gap between these viruses. But our study strongly suggests that sampling of more wildlife species will reveal viruses that are even more closely related to Sars-CoV-2 and perhaps even its direct ancestors, which will tell us a great deal about how this virus emerged in humans,” Shi said.

“Our work sheds more light on the evolutionary ancestry of Sars-CoV-2.”

Current Biology is affiliated with Cell, a peer-reviewed scientific journal.