Page 23 - The Restless Earth Fossils

2

The Tortuous

Road to Fossilhood

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A MOUNTAIN LION KILLS A YOUNG DEER TO EAT AND PROVIDE FOOD
for her cubs. Coyotes, ravens, and other scavengers eat their
fill of the leftovers and scatter the bones. Microscopic organ-
isms, mostly bacteria and fungi, break down living tissue into
the atoms and molecules of which they are composed. These
recycling processes, operating over Earth’s entire 4.6-billion-
year history, have ensured that life goes on. Carbon atoms that
build the framework of a fat molecule in a person’s big toe may
once have nestled in muscle tissue in a T. rex’s jaw. An oxygen
atom from a protein molecule consumed in yesterday’s hot dog
may have passed through the lungs of Cleopatra. Fortunately,
for anyone curious about the nature and evolution of past life
on Earth, our planet does fail to recycle everything quickly
in a straightforward way. Sometimes her restless forces make
fossils.

e(rosion)-Worlds and d(eposition)-Worlds
Kirk Johnson, a paleobotanist at the Denver Museum of Nature
and Science, likes to talk about D-Worlds and E-Worlds. In

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