Niles Eldredge, born in 1943, American paleontologist who, with fellow paleontologist Stephen Jay Gould, developed the theory of punctuated equilibria, which states that evolutionary changes occur in relatively short, abrupt bursts after long periods in which few changes take place (see Evolution: Development of Evolutionary Theory: Punctuated Equilibria).

Born in Brooklyn, New York, Eldredge attended Columbia University, where he received an undergraduate degree in anthropology in 1965 and a Ph.D. degree in geology in 1969. He served as adjunct assistant professor of geology at Columbia and assistant curator of invertebrate paleontology at the American Museum of Natural History until 1974, when he was appointed associate professor at Columbia and associate curator at the Museum. Eldredge held a concurrent position as adjunct professor of biology at the City University of New York from 1972 to 1977. He was named curator of the Department of Invertebrate Paleontology at the Museum of Natural History in 1979, retired from Columbia in 1981, and in 1984 accepted the directorship of the Department of Invertebrate Paleontology at the Museum.

Eldredge began studying the mechanisms of evolutionary change while working on his doctoral thesis, a project that focused on the trilobite, an early ancestor of the horseshoe crab that lived during the Paleozoic Era 570 to 250 million years ago. After several analyses of the trilobite fossil record, Eldredge concluded that trilobites evolved in short, concentrated bursts, rather than the gradual and continuous change predicted by Charles Darwin in his theory of evolution. In 1972 Eldredge collaborated with Gould to publish the theory of punctuated equilibria, which attempts to reconcile the discontinuities between the fossil record and the Darwinian theory of evolution. In his theory of punctuated equilibria, Eldredge postulates that species remain unchanged for hundreds of thousands of years, only to be abruptly replaced by newer and more successful forms—sporadic changes that appear as “punctuation” in the fossil record.

Eldredge is the author of more than 160 publications, including The Monkey Business: A Scientist Looks at Creationism (1982), Time Frames (1985), Fossils: The Evolution and Extinction of Species (1991), The Miner's Canary (1991), Reinventing Darwin (1995), and Dominion (1995).