Around 1850, sailors drove giant Galápagos tortoises to extinction, keeping them as live food because they could survive for up to a year without food or water; then scientists found mysterious ‘alien’ survivors in 2000

For more than a century, scientists believed one of the Galápagos Islands had lost its giant tortoises forever. Then, high on a remote volcanic landscape on another island, researchers encountered animals whose unusual shells raised a question that seemed almost impossible: could a tortoise thought extinct 150 years ago still have descendants alive somewhere in the archipelago?

The discovery came in 2000 during an expedition to Wolf Volcano on Isabela Island, the highest point in the Galápagos. Researchers noticed giant tortoises whose distinctive, saddle-shaped shells did not fit neatly with the population they expected to find there. Unsure of what they had encountered, they began referring to them as “aliens,” according to James Gibbs, a conservation scientist who was involved in the research and later work on the population, in an account published by CNN.