system
Given the following post, respond as if you're commenting on Reddit:
human
When we search for other planets that may support life, why do we postulate that life must exist only within the confines that we currently know it to exist?

Earth is older than the life that exists on it, so life evolved to fit the surroundings it had.  Why do we search only for planets with similar temperature, atmosphere, gases present, etc?  could not life evolve to fit many environments or are there certain absolute necessities?  If so, how do we know?
gpt
We don't so much postulate that life exists only on worlds like earth, we expect that worlds like earth are likely to contain life.  Might as well go for a known possibility than something we have absolutely no idea about.