He believes virus evolved generalist capability still bats .Because bats infects widely distributed southern central China , virus ample opportunity jump people , even though seems done one known occasion.Robertson ’ thesis explains one far found trace SARS2 intermediate host human populations surveilled December 2019.It would also explain puzzling fact SARS2 changed since first appeared humans — ’ need could already attack human cells efficiently.One problem idea , though , SARS2 jumped bats people single leap ’ changed much since , still good infecting bats.And seems ’ t. “ Tested bat species poorly infected SARS-CoV-2 therefore unlikely direct source human infection , ” write scientific group skeptical natural emergence.Still , Robertson may onto something .