Re 1) the codons, according to Christian Drosten, have precedence for evolving naturally in viruses. That could be because viruses evolve much faster than e.g. animals. Source: search for ‘codon’ and use translate here: https://www.ndr.de/nachrichten/info/92-Coronavirus-Update-Woher-stammt-das-Virus,podcastcoronavirus322.html
The link also has a bunch of content about the evolution of furin cleavage sites, from a leading expert.
Re 1) the codons, according to Christian Drosten, have precedence for evolving naturally in viruses. That could be because viruses evolve much faster than e.g. animals. Source: search for ‘codon’ and use translate here: https://www.ndr.de/nachrichten/info/92-Coronavirus-Update-Woher-stammt-das-Virus,podcastcoronavirus322.html
The link also has a bunch of content about the evolution of furin cleavage sites, from a leading expert.