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The Two Faces of Gaia The Medea Hypothesis: Is Life on Earth Ultimately Self-Destructive?, Peter Ward, Princeton and Oxford: Princeton University Press, 2009.
Reviewed by Kent Peacock
A distinguished earth scientist, Peter Ward has spent his career studying the mass extinctions that punctuate the turbulent history of life. In The Medea Hypothesis, a rich and challenging book, he uses disconcerting results from his gloomy science to criticize James Lovelock's Gaia hypothesis, and sets forth, in occasionally rough-hewn but urgent prose, a stern blueprint for humanity's future.
Scientific paradigm shifts have a way of sneaking up unexpectedly. Ward is among a group of earth scientists that has shown how many things we thought we knew about the history of life are wrong. He argues that only the K-T extinction, which wiped out the dinosaurs 66 million years ago, can be decisively linked with a major impact. Other extinctions, including the Permian near- total wipeout of life 250 million years ago, were mostly caused by climate change. Evidence exists in the layers of black shale that mark the extinction events at the boundaries between geological eras. Such deposits are formed only when the seas become anaerobic, like the deep waters of today's Black Sea.
"Anaerobic"...