The Yangtze River dolphin, often called the baiji, was known to be low in numbers, and the expedition had feared that they might find only a few dozen individuals. To find none at all was heartbreaking. A creature that had been swimming the waters of the Yangtze for at least 20 million years had come to the end of the line. Sure, there might be one or two individuals left that the researchers had missed, but they won’t be enough to keep the species alive. As 2006 drew to a close, the baiji was declared functionally extinct, and mankind had achieved a new first. We’d killed our first dolphin.

Human beings are currently causing the greatest mass extinction of species since the extinction of the dinosaurs 65 million years ago. By 2030, a quarter of the Earth’s mammals will be gone forever.