Another Group of Scientists Calls for Further Inquiry Into Origins of the Coronavirus Researchers urge an open mind, saying lack of evidence leaves theories of natural spillover and laboratory leak both viable. Bats being collected for research and analysis in Guandong Province, China, in 2019. “Theories of accidental release from a lab and zoonotic spillover both remain viable,” scientists wrote.Credit...EcoHealth Alliance May 13, 2021Updated 2:33 p.m. ET A group of 18 scientists stated Thursday in a letter published in the journal Science that there is not enough evidence to decide whether a natural origin or an accidental laboratory leak caused the Covid-19 pandemic.