3 ms·

> No it doesn't. They can be neutral. That's a fair point. Properly I guess we should try to quantify the number of samples expected before we observe an FCS i

> No it doesn't. They can be neutral. That's a fair point. Properly I guess we should try to quantify the number of samples expected before we observe an FCS if it's neutral, but that math seems nontrivial. It's at least definitely not beneficial, though. I do agree that the FCS could have evolved naturally, though I guess we'll continue to disagree on the relative probabilities of natural vs. lab-inserted. That sick pig was probably infected with each virus for days or longer, so that coinfection seems less unlikely to me than a simultaneous species jump and mutation to create the FCS (since those are both roughly instantaneous by comparison). I'm not sure what I'd consider the most likely zoonotic path now; the close identity between the BANAL and SARS-CoV-2 spikes seems like it removes the need for an intermediate host with human-like ACE2, though it's pretty mysterious.

lamontcg 4y ago
> a simultaneous species jump and mutation to create the FCS (since those are both roughly instantaneous by comparison). I don't know why you think this is necessary. The FCS shouldn't preclude the infection continuing in the original species, like I said it probably doesn't infectivity in bats and is neutral. And if the intermediate animal was infected with a common coronavirus for the species, all it takes is coinfection from a bat with the precursor to SARS-CoV-2 and a recombination event to create the FCS. Animals and humans across china are almost certainly getting infected with novel sarbecoviruses from bats every day. Most of them don't go anywhere. This one got "lucky" and stole some genetic material which made it better in the new host organism and now it is off to the races. Which is unlikely, but, again, pandemics are unlikely.
- tripletao 4y ago
  Assuming the FCS is neutral in bats (which I don't think we could prove or disprove without more sampling, but which I agree is possible), I agree that the mutation wouldn't have to happen concurrently with the species jump. Even if the FCS is negative in bats, it's also possible that the FCS evolved naturally in a different animal host. I agree there's no evidence to exclude those scenarios; I just don't see any specific evidence to favor them either.

lamontcg 4y ago

> a simultaneous species jump and mutation to create the FCS (since those are both roughly instantaneous by comparison). I don't know why you think this is necessary. The FCS shouldn't preclude the infection continuing in the original species, like I said it probably doesn't infectivity in bats and is neutral. And if the intermediate animal was infected with a common coronavirus for the species, all it takes is coinfection from a bat with the precursor to SARS-CoV-2 and a recombination event to create the FCS. Animals and humans across china are almost certainly getting infected with novel sarbecoviruses from bats every day. Most of them don't go anywhere. This one got "lucky" and stole some genetic material which made it better in the new host organism and now it is off to the races. Which is unlikely, but, again, pandemics are unlikely.

tripletao 4y ago
Assuming the FCS is neutral in bats (which I don't think we could prove or disprove without more sampling, but which I agree is possible), I agree that the mutation wouldn't have to happen concurrently with the species jump. Even if the FCS is negative in bats, it's also possible that the FCS evolved naturally in a different animal host. I agree there's no evidence to exclude those scenarios; I just don't see any specific evidence to favor them either.