|
Some 250 million years ago, the earth suffered
the greatest biological crisis in its history. Around 95
percent of all living species died out -- a global catastrophe
far greater than the dinosaurs' demise 65 million years
ago. How this happened remains a mystery. But there are
many competing theories. Some blame huge volcanic eruptions
that covered an area as large as the continental United
States; others argue for sudden changes in ocean levels
and chemistry, including burps of methane gas; and still
others cite the impact of an extraterrestrial object as
responsible, similar to what caused the dinosaurs' extinction.
Extinction is a paleontological mystery
story. Here, the world's foremost authority on the subject
provides a fascinating overview of the evidence for and
against a whole host of hypotheses concerning this cataclysmic
event that unfolded at the end of the Permian.
Erwin begins by setting the scene, taking
us from the 250-million-year-old early Triassic rocks of
the dry mesa of Utah -- where the fossils, few and far between,
are almost identical to those of the same age in northern
Italy, Iran, and China -- to the richly abundant, 256-million-year-old
Permian fossils of the Guadeloupe Mountains of Texas. After
introducing the suite of possible perpetrators and the types
of evidence paleontologists seek, he unveils the actual
evidence -- moving from China, where much of the best evidence
is found; to a look at extinction in the oceans; to the
extraordinary fossil animals of the Karoo Desert of South
Africa. Erwin reviews the evidence for each of the hypotheses
before presenting his own view of what happened.
Although full recovery took tens of millions
of years, this most massive of mass extinctions was a powerful
creative force, setting the stage for the development of
life as we know it today.
Douglas H. Erwin is Senior Scientist
and Curator in the Department of Paleobiology at the Smithsonian's
National Museum of Natural History and an External Faculty
Member of the Santa Fe Institute, He began researching the
end-Permian mass extinction in the early 1980s and has traveled
many times to China, South Africa, and Europe seeking its
causes.
|
