If that happened, I think we'd be able to determine that by sampling and analyzing the microbes.
I think a more interesting concept would be exchange of microbes between Venus and Earth at some point in their distant past, and then could we might be able to date that (those) event (s) via their molecular clocks (https://en.m.wikipedia.org/wiki/Molecular_clock)
I think a more interesting concept would be exchange of microbes between Venus and Earth at some point in their distant past, and then could we might be able to date that (those) event (s) via their molecular clocks (https://en.m.wikipedia.org/wiki/Molecular_clock)