After the ice recedes, buried in the moraine and eventually
in geologic layers below will be an unnatural concentration
of a reddish metal, which briefly had assumed the form of
wiring and plumbing. then it was hauled to the dump and
returned to the earth. the next toolmaker to arrive or
evolve on this planet might discover and use it, but by then
there would be nothing to indicate that it was us who put it
there.
which claim does the excerpt most clearly support