If we could genetically engineer humans to survive on all kinds of worlds
in our Sol system, that would virtually guarantee the survival of our
species somewhere in the galaxy.

As time and our society advances, we won't be staying the same
anyway. Look at how nuts people get about plastic surgery. Just
imagine when we can manipulate the genetics of ourselves and our
children - including and especially before they are born - to look and
stay younger and prettier for centuries.

Combine that with the ability to strike out on a new world away from
the crowded and dominated old one and look out Milky Way!