In many ways, Madagascar is a biologist's dream, a real-life experiment in how isolation on an island can spark evolution. About 90% of the plants and animals there are found nowhere else on Earth. But these plants and animals are in major trouble, thanks to habitat loss, over-hunting, and climate change. Of the 219 known mammal species on the island, including 109 species of lemurs, more than 120 are endangered. A new study in Nature Communications 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.