Mammals first appeared on Earth over 200 million years ago, scuttling around alongside the dinosaurs as little mouse-sized creatures. But after the asteroid hit 66 million years ago, it was their time to shine ‪—‬ and the Age of Mammals began.

But the path to understanding our own branch of the animal kingdom hasn’t been straightforward. In this excerpt from “The Story of the Mammals in 25 Discoveries” (Columbia University Press, 2026), author Donald R. Prothero looks at a time when philosophers and early naturalists believed giants roamed the Earth and explores the idea that extinction was heresy.

The Story of the Mammals in 25 Discoveries: Amazing Fossils and the People Who Found Them

Columbia University Press

The Story of the Mammals in 25 Discoveries: Amazing Fossils and the People Who Found Them

Donald R. Prothero takes readers on a journey through the history of mammals, opening a window onto the worlds of some of the most incredible and peculiar animals that ever lived. He tells the dramatic stories of fossil findings and the paleontologists who unraveled them, showing how scientific ingenuity advanced our knowledge of both ancient and present-day mammals.