LiveScience: During the last Ice Age, huge mammals roamed North America. Those mammoths, saber-toothed cats and giant sloths disappeared about 12,000 years ago -- the same time as humans arrived and Earth's climate warmed from its glacial chill.
Scientists have long debated the cause of the mass extinction, whether humans or climate change. But now, researchers are beginning to turn from investigating the cause to better understanding its impact. The loss of so many of those large species, or megafauna, could...