Comment by Michael B. Weissman

An influential paper by Pekar et al. published in Science in 2022 claimed that Bayesian analysis of the molecular phylogeny of early SARS-CoV-2 cases indicated that the likelihood that two successful introductions to humans had occurred was greater than the likelihood that just one had occurred. After correcting a fundamental error in Bayesian reasoning, the results presented in that paper imply larger likelihood for a single introduction. That correction reduces the compatibility of the results with the wet-market zoonosis account.