Extinctions on Ice

Abstract

Mass extinctions of North American mammals at the end of the last Ice Age continue to draw scientific attention and debate It is a paleontological mystery that falls under the heading Now you see them, now you don't. last Ice Age, or Pleistocene epoch, extended from 1.6 million to 10,000 years ago, yet not until its final two millennia did large numbers of North American animals make their swan song. In a blip of time in the 3.5billion-year history of life on earth, the fossil evidence indicates that 35 classes of mammals became extinct in North America and most vanished altogether. What caused the virtually simultaneous demise of mammoths, mastodons and saber-toothed cats, not to mention native horses, ground sloths, native camels, armadillo-like glyptodonts, giant peccaries, mountain deer, giant beavers, four-pronged antelopes, dire wolves, native lions and giant short-faced bears? Scientists have grappled with this question for nearly two centuries, and, as evidenced by a recent symposium at the Smithsonian Institution in Washington, D.C., the debate is not about to cool down. There is broad agreement that the extinctions occurred 12,000 to 10,000 years ago, and probably more precisely about 11,000 years ago. But the cause of this disappearing act is attributed either to hunting by early inhabitants of the New World, climate change or some combination of the two. The seemingly incredible notion I have defended is that prehistoric people obliterated hundreds of species of large mammals, and even more species of smaller animals as oceanic islands were populated, in a very brief moment early in the colonization of the globe, says ecologist Paul S. Martin of the University of Arizona in Tucson.