system
Given the following post, respond as if you're commenting on Reddit:
human
If humans were to become a multi-planet species, could humans on Planet A and humans on Planet B eventually become two separate species over a vast length of time in two possibly different environments?
gpt
If humans were to become a multi-planet species then one would assume that they would be able to exchange genetic material between the populations on the various planets. The only way they would ever diverge into separate species is if the planets were somehow reproductively isolated from one another for a *very* long time. Long enough for the two populations to somehow evolve innate barriers to reproduction.    
    
So the only way this could really happen would be if humans gained and then lost the ability to travel between planets. If all of the populations were reproductively isolated, then they would probably speciate given enough time.