Everything is based upon life as we know it. An alien race could come here and show us that everything we thought we knew is completely wrong. There's species on this planet that live in severe environments that science thought was impossible. There could be non carbon based life or even non organic life. Theres so much we don't know of the universe bc we haven't been ooutside the Earth and the moon. There's just so much we can't know until we are out there ourselves.