Giant 10-foot-tall elephant birds, with eggs eight times larger than an ostrich's. Sloth lemurs bigger than a panda, weighing in at 350 pounds. A puma-like predator called the giant fosa. They sound like characters in a child's fantasy book, but along with dozens of other species, they once really roamed the landscape of Madagascar. Then, after millions of years of evolution in the middle of the Indian Ocean, the populations crashed in just a couple of centuries. Scientists know that over the past 40,000 years, most of Earth's megafauna – that is, animals human-size or larger – have gone extinct. Woolly mammoths, sabre tooth tigers and countless others no longer roam the planet. What's remarkable about the megafaunal crash in Madagascar is that it occurred not tens of thousands of years ago but just over 1,000 years ago, between A.D. 700 and 1000. And while some small populations survived a while longer, the damage was done in a relatively short amount of time. Why? Over the last three years, new investigations into climate and land use patterns, human genetic diversity on the island and the dating of hundreds of fossils have fundamentally changed scientists' understanding of the human and natural history of Madagascar. As two paleoclimatologists and a paleontologist, we brought together this research with new evidence of megafaunal butchery. In doing so we've created a new theory of how, why and when these Malagasy megafauna went extinct. Last of the giants: What killed off Madagascar's megafauna a thousand years ago? Cows cannot catch a break.