The scientific community has begun to question one of the pillars of modern thought: Charles Darwin's theory of evolution. If it is a slow, continuous process whereby one species gradually changes to a new one, as Darwin believed, why are there missing links in the fossil record? Based on their detailed research, two eminent palaeontologists, Niles Eldredge and Stephen Jay Gould concluded that a species, once evolved, rarely undergoes change and that the evolution of a new species occurs only periodically, in relatively rapid bursts. Strutture del tempo by Niles Eldredge (the article he wrote with S. J. Gould in 1976 is appended) is the most complete and compelling exposition of what has been called the 'theory of punctuated equilibria', known in Italy only through a few elementary and popular essays.
 

Niles Eldredge was born in Brooklyn in 1963, is a paleontologist and curator of the invertebrate collection at the American Museum of Natural History in New York. Together with Stephen J. Gould he developed the theory of punctuated equilibria, one of the most original in contemporary Darwinism. His most recent books include Strutture del tempo (Hopefulmonster, 1991) and l canarino del minatore (Sperling & Kupfer, 1994). For Einaudi he published Ripensare Darwin. Il dibattito alla Tavola Alta dell'evoluzione ("Biblioteca Einaudi", 1999), La vita in bilico ("Einaudi Tascabili", 2000) and Perché lo facciamo ("Gli struzzi", 2005).