Over 10,000 years ago in the Americas, there were many more large mammals than today epitomized by the mammoth. The extinction of woolly mammoths and other large mammals more than 10,000 years ago may be explained by the same type of cascade of ecosystem disruption that is being caused today by the global decline of predators such as wolves, cougars and sharks, life scientists report July 1 in the cover article of the journal Bioscience.