The website Rootclaim, which uses Bayesian analysis to estimate the probabilities of various hypotheses about news events, claims to have ascertained that with high (approximately 75% probability), SARS-CoV-2 was produced by gain-of-function research in a lab (most likely the Wuhan Institute of Virology (WIV)) rather than through transfer from animals to humans, as is commonly believed:
Two of the key pieces of evidence that the site claims point to a lab origin are:
(1) SARS-CoV-2 is a "chimera" - it contains genetic code from two other viruses - and these other viruses are likely to have been available to the WIV to combine but are not likely to have been combined in nature.
(2) SARS-CoV-2 contains a "furin cleavage site" - a feature making it more contagious - and the fact that the cleavage site arose via insertion rather than mutation, as well as the fact that it uses the CGG codon for arginine, are both features that are likely to have occurred if the virus was engineered but are less likely to occur if the virus was natural.
Are these claims accurate? Is it true that these features point toward a lab origin? Are there other features that point away from a lab origin that have not been analyzed by this site, or is the analysis as a whole accurate?