Twilight of the Mammoths: Ice Age Extinctions and the Rewilding of America is the eighth volume in the University of California Press's series on organisms and environments, whose unifying themes are the diversity of plants and animals, the ways in which they interact with each other and with their surroundings, and the broader implications of those relationships for science and society. We seek books that promote unusual, even unexpected, connections among seemingly disparate topics, and we encourage projects that are distinguished by the unique perspectives and talents of their authors. Previous volumes have spanned the ecology of Arizona grasslands, Seri ethnoherpetology, and the biology of Gila monsters.

Twilight of the Mammoths is an insightful, engrossing account of the end of the famous Pleistocene ice ages and of the first colonization by humans from Asia of the New World. Told in the form of a personal journey, Paul Martin's book covers his own boyhood bird-watching, graduate work in evolutionary biology, and a distinguished academic career; it culminates in a daring plan to truly rewild North America. This is a story of science in action, of arduous fieldwork and exciting discoveries, of intellectual puzzles and clashing theories. It is also a work of high-stakes advocacy, in which Martin marshals the evidence for his controversial theory that humans, within a remarkably short time after our arrival, caused the extinction of more than 30 genera and 40 species of large mammals. More than that, Martin aims to convince us to take the long view, to learn from our collective past so that we can enrich the future of life on earth. He wants us to regard feral horses and burros as repatriated natives rather than introduced pests, to welcome Asian elephants as surrogates of extinct proboscideans. He challenges us with these and other bold proposals to ask: Why did we in North America inherit such an impoverished mammal fauna? What kind of world will our children inherit?

Imagine a Serengeti-like vista on the North American Great Plains, a region that actually housed and fed not only roughly 30 million bison, but also countless individuals of dozens of other large mammal species. Realize that we are not conjuring an ancient fantasy here, that Twilight of the Mammoths is not about some furry version of Jurassic Park, only vaguely based on reality. Until about 13,000 years ago—just 130 centuries, or a few times as long ago as the pharaohs reigned over Egypt— western North America really did harbor a megafauna that surpassed Africa's modern biota in species richness. There were several species of wild horses and camels, an armadillo relative the size of a small car, and giant ground sloths, as well as short-faced bears, dire wolves, saber- and scimitar-toothed cats. There were somewhat larger versions of our contemporary cheetahs and lions, and there were several species of mastodons and mammoths, relatives of living elephants. All of those large New World mammals are gone now, vanished in a heartbeat of geological time, and yet almost all of the plants and smaller species that lived with them persist today. Some of those surviving organisms, like the Osage orange tree, are still here only because we have taken on the ecological roles of extinct megafauna, in this case seed dispersal; one of our surviving ungulates, the pronghorn, is capable of locomotor feats that only make sense in the presence of a high-speed predator like the now-extinct North American cheetah. Today the sole substantial remnant of what was once a global Pleistocene megafauna is in Africa, a rapidly changing landmass on which people are killing each other in tragic numbers in response to shrinking resources. Throughout the world, large vertebrates have been reduced to life in fragmentary habitats and often to dangerously low population levels if they are to survive and make long-term evolutionary adjustments to environmental change.

Paul Martin is a true visionary, a time traveler who thinks across the expanses of prehistoric millennia and entire continents with the ease with which most of us locate a car we parked yesterday. His professional accomplishments include a classic work on amphibian and reptile bio-geography, pioneering studies of palynology and plant ecology, and an illustrious legacy of former students and research associates. Paul is a gifted storyteller, a self-described lover of "tempting diversions," and I doubt anyone else could make standing chest-deep in extinct sloth dung sound so magical. Soon after identifying the pollen of an abundant local plant in that 13,000-year-old manure, this voracious naturalist tries out the leaves and flowers of globe mallow on his own digestive tract. Paul is by temperament affable rather than cantankerous, and here he generously confronts the full panoply of his critics. He faces squarely "overchill" and "overill," the alternative hypotheses that climate or disease killed off the Pleistocene megafauna, and he candidly confronts charges that the overkill theory reflects cultural insensitivity.

Twilight of the Mammoths is an intellectual detective story, one that remains in part controversial but that also resonates marvel and hope. When I visited Nairobi National Park, surrounded for the first time in my life by thousands of large wild herbivores and alert to the unseen presence of their predators, I experienced a surprising nostalgia for our own, largely extinct North American savanna faunas. Now Paul Martin's life's work challenges all of us who care about nature to be hopeful rather than sad, to think very big. In that spirit he gives us the thrill of biological exploration, the facts as they have emerged thus far, and some of the problems remaining to be solved. His legacy amounts to a profound challenge—that we face up to the near cessation of large vertebrate evolution because of habitat destruction and human persecution. Martin asks us to accept that humans are, willy nilly, in charge of the fate of wilderness and to consider an optimistic alternative to extinction. In this captivating book he says, look at the ecological processes and evolutionary potential that we've so recently lost—in so far as we can, let's bring them back!

Harry W. Greene February 2005

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