Mankind has recently come to the shocking realization that our ancestors survived hundreds of abrupt and severe changes to Earth's climate. In this unique travelogue, William H. Calvin takes us around the globe and back in time, showing us how such cycles of cool, crash, and burn provided the impetus for enormous increases in the intelligence and complexity of human beings and warning us of human activities that could trigger similarly massive shifts in the planet's climate."Calvin leads us along a trail that links sudden worldwide cooling, to the origin of our large brains and modern human behavior... His presentation differs from the others in that it really is an attempt to think globally about past and present climate change and its possible effects on creatures and their evolution." Scientific American"Calvin mixes very difficult and momentous topics with simple momentary observations, placing his enormous subjects in a personal, humanistic, and conversational perspective. . . . Amusing, alarming, reassuring, and awe inspiring by turns. It is as if the reader is partaking of a conversation with a brilliant and well-informed friend who is so full of ideas that no one else can get a word in edgewise." Virginia Quarterly ReviewWinner of the 2002 Phi Beta Kappa award for science as literature and of the 2006 Kistler Book Award.