CAST IN STONE

Dedicated to the memory of Dr. L. Beverly Halstead,geologist, paleontologist,
scholar, and explorerJune 13, 1933-April 30, 1991.

Cast your thoughts back to the dawn of modern geology more than 100 years ago.
From quarries, from cliff sides, from stones underfoot, the remains of strange
and terrifying creatures emerged. Bones bigger than a full-grown human, heads
the size of horse carriages, a single claw dwarfing a sickle, stunned our
great-grandparents. Science, the Victorians thought, would find the answer.

Today we know what fossils represent: Fantastic animals once inhabited this
planet. But the worlds that nurtured these beasts and scores of others are long
gone. Only the stones remember.

Some stones harbor remarkably clear remnants of long-extinct animals. From
Germany comes a superb example of `Archaeopteryx,' a dinosaur, with its
unmistakable bird-like plumage preserved. Worldwide, you can find pristine
examples of trilobites, which for millions of years scurried across the floors
of hot, stagnant seas. Yet even the best-preserved specimens leave many
questions unanswered. `What color were you? How well did you see? What sorts of
sounds filled the air at night?' We can extrapolate, we can argue, we can
wonder, but we can never really know.

A chance marriage between a living thing and the eternity of stone gives birth
to fossils. Sometimes it is the living things themselves that fossilize, bone
and occasionally tissue almost lovingly superseded by minerals leached from the
surrounding rock.

In the fossil record we watch life forms emerge, flourish, and become extinct.
We read that continents, climates, and even the location of the North and South
poles shift like a fluid. Oceans appear and disappear. Landscapes may appear
timeless and unchanging, but they reflect catastrophic changes in the nature of
this planet.

Science has coaxed the rocks to divulge their memories of worlds past. We now
understand fossils in a way our ancestors could not. the message is grim:
Ninety-nine percent of the species that have inhabited this planet are now
extinct. No matter how superbly adapted an animal becomes, its species, and its
world, finally fails.

There is no doubt that human activities are altering the ecology of this planet.
Some say we are on the verge of destroying the very world that supports our
species. But Earth itself has destroyed its own ecology scores of times in the
past, made a place that was once hot cold, added or erased rivers, shifted its
winds. It will continue to do so even without human interference.

Photographs are reprinted from `Fossils: The Evolution and Extinction of
Species' by Niles Eldredge, photographs by Murray Alcosser. Published 1991 by
Harry N. Abrams, Inc., New York. All rights reserved. Photographs 1991 Murray
Alcosser. All specimens illustrated are from the collection of the American
Museum of Natural History.