https://www.sciencedaily.com/releases/2021/06/210624141537.htm

The origins of the ongoing COVID-19 pandemic remain unclear. The first officially identified case occurred in early December 2019. However, mounting evidence suggests that the original case may have emerged even earlier.

To help clarify the timing of the onset of the pandemic, Roberts and colleagues repurposed a mathematical model originally developed by conservation scientists to determine the date of extinction of a species, based on recorded sightings of the species. For this analysis, they reversed the method to determine the date when COVID-19 most likely originated, according to when some of the earliest known cases occurred in 203 countries.