Page 21 - The Restless Earth Fossils

20 Fossils

What kinds of questions can these and other fossil discoveries
help scientists answer?

F Fossils help us know when things happened in the history
of the Earth. Scientists know that Sauroposeidon lived at a
later time than Apatosaurus, for example, because it was
found in sedimentary rocks that overlay the kind of rocks in
which Apatosaurus was found—a fact that Steno would have
appreciated.
F Fossils provide glimpses of some of the lost worlds of deep time.
Finds connecting insects to plants that they had pollinated
provide valuable information about when certain ecological
relationships between organisms evolved.
F Fossils document the major features of evolutionary change. The
discovery that a predatory dinosaur like Velociraptor possessed
feathers lends support to the theory, based on anatomical and
other evidence, that birds are the direct descendants of one
branch of dinosaurs. (More traditional dinosaurs are now
often referred to as “non-avian or non-bird dinosaurs.”)
F Fossils provide clues to the reasons for extinctions—both normal
and catastrophic kinds. The kind and abundance of various
fossils change dramatically at extinction boundaries. In
fact, these changes define such boundaries. Fossils provide
scientists with clues to understanding the mechanisms that
cause major extinction events, which will provide guidelines
to prevent human behaviors that might start or accelerate
catastrophic extinction events today.
F Primate fossil remains provide insights into human evolution
and reveal our intimate and necessary connections to the rest of
the living world. The ancient human species found on Flores
stood only three feet tall. Human evolution on a small,
isolated island resulted in the same kind of dwarfism demon-
strated by other animals, like mammoths, that were isolated
in a similar fashion. Fossil discoveries indicate that at various
points over the last 2 million years, several human species

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