Book review: When Life Hearly Died (Michael J. Benton)

Michael Benton

WHEN LIFE NEARLY DIED

The greatest mass extinction of all times
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Book review by Anthony Campbell. The review is licensed under a
[6]Creative Commons License.
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Although this book is partly about the great end-Permian mass
extinction it is also a historical account of how ideas about
about catastrophism in palaeontology have changed in the last 200
years. Benton traces how views of mass extinctions have developed
since the early nineteenth century, when Charles Lyell advocated
'uniformity' -- the view that the processes shaping the earth were
those we can still see in action today. Arguments about this have
continued down to our own time, though a decisive shift occurred
in the twentieth century with the widespread acceptance of impact
as an explanation for the demise of the dinosaurs. As a student
Benton himself was taught by anti-catastrophists, but now he
preaches asteroids and mass extinctions to his students.

The modern view is that there have been several mass extinctions
in the past -- at least five. They were characterised by the loss
of 20%--65% of families and 50%--95% of species. Whether mass
extinctions are different from 'normal' extinctions is uncertain,
though they may be. During a mass extinction survival is largely a
matter of luck, although geographically separate groups may be
more likely to survive. Some mass extinctions were virtually
instantaneous though others lasted for up to 10 million years.
Recovery has usually taken about 10 million years although after
the end-Permian event it took ten times as long.

The date of the end-Permian event is now fairly well established
at about 251 million years ago, with a margin of about 700,000
years. At least 90% of the species alive at the time were lost.
One of the principal survivors was a reptile called Lystrosaurus,
probably because it was so widespread; Benton says it was one of
the most successful reptiles of all time. It found itself in an
almost empty world after the catastrophe.

The cause of the end-Permian extinction is still unknown and some
pretty wild ideas have been proposed. Benton thinks the most
likely explanation is a complex series of interactions triggered
by the prolonged volcanic eruption known as the Siberian Traps.
Worldwide devastation was caused by the production of various
gases, including carbon dioxide, sulphur dioxide. and chlorine.
The result was a runaway greenhouse effect and global warming.

The book concludes with a consideration of the so-called Sixth
Extinction, which we are causing by global warming. Benton points
to numerous uncertainties concerning biodiversity and the real
rate of species loss and says that, paradoxically, we know more
about past extinctions than we do about the present one. The book
ends with questions, not answers. "How diverse is life? How does
the world react to human intervention? What will happen in the
next 100 years? Where did life come from? How resilient is life to
crisis?"

There is a lot of information in this book though I think it is
rather over-long, with some digressions that might have been
pruned with advantage.

See also Extinction, by Douglas H. Erwin.

24 April 2008
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%T When Life Nearly Died
%S The greatest mass extinction of all times
%A Michael J. Benton
%I Thames & Hudson
%C London
%D 2003
%G ISBN 0-500-05116-X
%P pp 336
%K palaeontology
%O illustrated
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--
Anthony Campbell - ac RemoveThis @acampbell.org.uk
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http://www.acampbell.org.uk (blog, book reviews,
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