Natural selection would continue to operate, but different traits would be more beneficial in various environments.
To me, the only scenarios that don’t seem “reasonable” to some extent are those which require that human nature cease to be human nature. The entire history (and known prehistory) of Earth makes it clear that people are always the same. The range of possible outcomes from any change in environment is limited by the fact that we are what we are.
I do think that modern technology has made us feel sufficiently invulnerable. As a result, too many of us feel safe in rejecting common sense.