David Baltimore: “When I first saw the furin cleavage site in the viral sequence, with its arginine codons, I said to my wife it was the smoking gun for the origin of..virus..These features make a powerful challenge to..idea of a natural origin for SARS2”
https://nicholaswade.medium.com/origin-of-covid-following-the-clues-6f03564c038
For reference, Baltimore not only is the co-discoverer of, reverse transcriptase, an enzyme used in all PCR-based COVID tests, but also is the co-inventor of the infectious-clone technology used to engineer genomes of viruses and to construct chimeric viruses.