It is clear from the passage that fossils ----.

Fossils are the remains of organisms which have
endured for fantastic periods of time. Fossils can be
bones or teeth or even plant or animal imprints
preserved in rock since prehistoric times. The
appearance of fossils in rock has been a source of
wonder and fascination to man for centuries. The
fossil of an ancient sea animal was even found
among the possessions of a prehistoric man. Many
people have tried to explain fossils. Aristotle believed
they were the remains of living creatures, but thought
the creatures grew in the rocks. Some people
believed that fossils were placed in rocks by evil
spirits. Other explanations were remarkably modern.
For example, Herodotus, an ancient Greek historian,
observed fossil seashells in the Libyan desert in 450
B.C. and guessed that the Mediterranean Sea had
once reached much farther south than it does today.