90% of the plants and animals on Madagascar are found nowhere else on Earth, but this treasure trove of evolution is under serious threat due to habitat loss, over-hunting, and climate change. In this study, researchers examined how long it took Madagascar's unique modern mammal species to emerge and estimated how long it would take for a similarly complex set of new mammal species to evolve in their place if the endangered ones went extinct: 23 million years, far longer than scientists have found for any other island.