If we discovered evidence of alien life, would we even realize it? Life on other planets could be so different from what we’re used to that we might not recognize any biological signatures that it produces.
Recent years have seen changes to our theories about what counts as a biosignature and which planets might be habitable, and further turnarounds are inevitable. But the best we can really do is interpret the data we have with our current best theory, not with some future idea we haven’t had yet… More about this article in the link below…
https://www.livescience.com/amp/why-no-alien-life-theories-bad.html