William Beebe on extinction:

"The beauty and genius of a work of art may be reconceived, though its first material expression be destroyed; a vanished harmony may yet again inspire the composer; but when the last individual of a race of living beings breathes no more, another heaven and another earth must pass before such a one can be again."

(We originally encountered this quote in the movie, Ghost Bird, and the producer of that film, Scott Crocker, recently shared it with us again.)