For me the "early slime" is more impressive than the
steps to the "higher" evolution.

Getting life into existance out of lifeless matter at all, even if very primitive, is more impressive than some further DNA changes
that created more complex variations.

(Although life could have originated somehwere else, and
was brought to earth on some comets, beeing much older than earth)

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Even if life had evolved into high creatures in other places,
they obviously did not get powerful enough so
that we notice them without any problem
(SETI etc)

If there where really some powerful Aliens, they
should have at least send out some sattelites to
serve as beacon, scan or even make contact. (even if they had to fly around forever)
Its not much outh there obviously.