Standard reminder that it took years to find SARS. https://www.nature.com/articles/d41586-017-07766-9
There are lots and lots of bat caves.
That, plus that the ease with which the virus jumped back to animals (deer, hamsters, mice, ferrets, cats, dogs) makes the search for a reservoir animal very difficult, as well as the fair chance that there were few enough of those (possibly only one) that that part of the evidence chain may well remain broken.
> That, plus that the ease with which the virus jumped back to animals
It is trivial to tell whether a variant is antecedent - this is how the absurd 'double jump' of lineage A and lineage B was necessary for Worobey to justify his thesis that the wet market was the origin of covid... twice
Without commenting on Worobey's thesis:
> It is trivial to tell whether a variant is antecedent
I'm sure all of the evolutionary biologists would love to have your level of confidence.
It's trivial when the differences and the timescales are large (and even then we get it wrong plenty of times). But it isn't trivial at all when the differences are minor and the timescales are close, in fact it can be really, really hard. Fortunately with COVID19 a lot of evidence was gathered in real time and preserved so there are a lot of theories that can be ruled out based on that.
One of the hardest problems is to figure out when there is an individual where more than one virus took hold at the same time and genetic material was exchanged between two strains rather than just a mutation. There is some - but inconclusive - evidence that this happened more than once during the COVID pandemic.
It's easy to say this, as neither you nor I have the requisite knowledge to prove/disprove your assertion. But I read threads like this one [1] or resources like this one [2] and realize that there are experts who are able to distinguish earlier and later variants.
Incidentally, I noticed that you edited your first response several times while I wrote this. The tone of what you wrote first was a bit less considered than the what I'm responding to now, but I hope it's ok to just leave it at this.