> "Decades" worth of mutations can happen in a single immune-compromised host in a matter of weeks.
SARS-CoV-2 has been circulating for a year now. The number of mutations it has undergone is a tiny fraction of the number of mutations separating RaTG13 and SARS-CoV-2.
> fwiw I'd love a source for that "decades" claim.
A paper in Nature Microbiology estimates the most recent common ancestor of RaTG13 and SARS-CoV-2 to be in the 1960s. The latest possible time of divergence is 2000.[1]
> RaTG13 is the closest virus found in the wild to SARS-CoV-2. Samples of it were shipped to the Wuhan lab, which does so-called "gain of function research"--AKA experimenting with artificially sped up mutation rates.
First of all, gain-of-function does not mean "artificially sped-up mutation rates." It normally refers to specific, targeted changes to the genome, done in order to test a particular hypothesis. What you're describing is a type of experiment never done before: passaging a virus thousands of times in order to generate a massively different virus. This would be an massively time- and labor-intensive experiment, with no apparent motivation.
Second of all, RaTG13 has never been isolated. It exists as fragments of RNA in a fecal swab. Its genome has been reconstructed from sequences of RNA samples, but actually extracting a replicating virus from a fecal swab is a major undertaking. To date, the WIV has only isolated three SARS-related coronaviruses, all of them much closer to the original SARS than to SARS-CoV-2. Before 2020, nobody cared much about viruses that are 20% different from the original SARS. If you read papers from the WIV before 2020, they're all about viruses like WIV-1, which is closely related to the original SARS.
