With SARS-Cov1 and MERS they were able to identify the cross-over host and find transitional stages that are somewhat adapted to human hosts but more successful in other host animals. It is not too late to find that of course, but it is becoming conspicuous in its absence. Also, the lab in Wuhan was basically trying to create SARS-Cov-2 and that isn't speculation its what their grant proposal says they were doing.