The only thing we REALLY know is that these types of coronaviruses originate in Southern China and somehow got to the point of being suspiciously well adapted to ACE2 by the time it exploded in Wuhan.
That, however, can also be achieved purely by natural causes over a long time - not just in a lab. Maybe Wuhan is simply the point at which the first very infectious form of SARS-CoV-2 occurred - not the first overall occurrence of any SARS-CoV-2 variant. And it provided a perfect environment to spread at its wet markets. If the virus originated in the West, maybe we would be shitting all over meat processing facilities now?
So, how many people would need to get infected to facilitate these mutations? We could possibly have missed SARS-CoV-2 infections with earlier virus strains that were vastly less infectious. It would take quite a lot of people to raise suspicions of anything other going on than nominal incidents of flu-like symptoms. So maybe the initial SARS-2 was basically SARS-1 with much less incidence of severe symptoms - so it slipped under the radar until it mutated, exploded in incidence and suddenly produced overwhelming hospitilization rates.
It's plausible, and could be proven very easily that this happened. Presumably, some progenitor strain is out there, spreading more slowly and making less of a mess. Eventually, a SARS-CoV-2 screen will turn it up and we'll sequence it. Then we will see a strain that's diverged from all other sequences in the phylogenetic tree, with a common ancestor back further than ~1ya.
That, however, can also be achieved purely by natural causes over a long time - not just in a lab. Maybe Wuhan is simply the point at which the first very infectious form of SARS-CoV-2 occurred - not the first overall occurrence of any SARS-CoV-2 variant. And it provided a perfect environment to spread at its wet markets. If the virus originated in the West, maybe we would be shitting all over meat processing facilities now?
So, how many people would need to get infected to facilitate these mutations? We could possibly have missed SARS-CoV-2 infections with earlier virus strains that were vastly less infectious. It would take quite a lot of people to raise suspicions of anything other going on than nominal incidents of flu-like symptoms. So maybe the initial SARS-2 was basically SARS-1 with much less incidence of severe symptoms - so it slipped under the radar until it mutated, exploded in incidence and suddenly produced overwhelming hospitilization rates.