Imagine researchers making frequent trips Wuhan Yunnan back , stirring bat guano dark caves mines , begin see possible missing link two places.Researchers could gotten infected collecting trips , working new viruses Wuhan Institute Virology.The virus escaped lab would natural virus , one cooked gain function.The direct-from-bats thesis chimera natural emergence lab escape scenarios.It ’ possibility ’ dismissed.But facts 1 ) SARS2 RaTG13 seem feeble affinity bat cells , one ’ fully confident either ever saw inside bat ; 2 ) theory better natural emergence scenario explaining SARS2 gained furin cleavage site , furin cleavage site determined human-preferred arginine codons instead bat-preferred codons .