having a structure identical to similar viruses found in bats.a subsequent mutation. However, the first known human cases involved lineage. To resolve this conundrum, the researchers analysed nearly 800 almost-complete viral genomes from samples taken before February 14th 2020, to identify the most likely evolutionary paths taken by the virus.
This analysis showed that, while both lineages were present in cases in the vicinity of the market, no samples contained either any transitional form or any shared common ancestor. It therefore seems likely that the lineages made independent leaps into human hosts: lineagea week or so later. Such multiple jumps from animals are common in coronaviruses. The viruses responsible for both the, which appeared in 2012, are also thought to have started with multiple spillover events.
Though the papers are preprints, their analysis has been praised by numerous independent researchers. Assuming they are indeed correct, rival hypotheses have a steep hill to climb. The most popular of these, as well as the most contentious, is that the virus escaped from a laboratory in Wuhan before triggering a “superspreader” event at the market.