A palaeontologist and evolutionary biologist with the American Museum of Natural History, Eldredge, together with Stephen Jay Gould, proposed the theory of punctuated equilibria, providing palaeontologists with an explanation for the patterns which they find in the fossil record. He has written several books for a general audience, including Time Frames: The Evolution of Punctuated Equilibria and Life in the Balance: Humanity and the Biodiversity Crisis.