And we men, the creatures who inhabit this earth, must be to them
at least as alien and lowly as are the monkeys and lemurs to us.  The
intellectual side of man already admits that life is an incessant
struggle for existence, and it would seem that this too is the belief
of the minds upon Mars.  Their world is far gone in its cooling and
this world is still crowded with life, but crowded only with what they
regard as inferior animals.  To carry warfare sunward is, indeed,
their only escape from the destruction that, generation after
generation, creeps upon them.