The viral lineage leading to the novel coronavirus SARS-CoV-2 might have been circulating unnoticed in bats for decades
Coronaviruses capable of infecting humans may have been circulating undetected in bats for decades.
Research suggests one of the closest known ancestors of the virus that causes Covid-19 emerged in bats between 40 and 70 years ago.
It has been poised for human crossover for some time, the scientists said.
And this casts further doubt on conspiracy theories that the virus causing Covid-19 was bioengineered or escaped from a laboratory, they added.
Prof David Robertson, of the University of Glasgow, worked on the study, published in the journal Nature Microbiology.
He said that while Sars-CoV-2 (the pandemic coronavirus) is genetically very close to the nearest known bat viruses, they are separated in time by several decades.
"If these viruses have been around for decades that means that they've had lots of opportunity to find new host species, including humans," said Prof Robertson.
The researchers compared the genetic make-up of Sars-CoV-2 with that of a close relative in bats, a virus known as RaTG13, and other related bat viruses.
They dated the time the two shared a common ancestor, and found they went along their own evolutionary pathways several decades ago.
Prof Mark Pagel of the University of Reading, who was not part of the study, said the work suggests that coronaviruses capable of infecting humans have been present in bats for perhaps 40 to 70 years but have gone undetected.
The viruses may have gone on to infect other wildlife, particularly those coming into close contact with each other through illegal wildlife trade. But to date, all the evidence points to bats being the important reservoir.
Previous research has suggested that pangolins might have played a role in the evolution of Sars-CoV-2, but the latest study suggests this is not the case.
Instead, pangolins may have picked up the virus more recently through contact with other wild animals through wildlife trafficking into China.