How do we survive in space? We can't, really. We have to bring along our usual environment. And we develop health problems for the lack of the one thing we can't bring along - gravity.
Bacteria are much more adaptable than humans, primarily because there are so many of them, and their generation times are so short that they can much more quickly adapt to a hostile environment.
Our DNA has changed a great deal. For example, if we began as a single pair of humans (a religious belief with which I agree) and our DNA did not change, we could have at most four alleles for each gene in our DNA. And yet, there are dozens of alleles in the human population for many of them, the majority of them useful.
Anything more than four must have evolved.