Evolutionary change that is either arrested or occurring at a very slow rate over long geologic periods.



a slow rate of the evolutionary process characteristic of certain systematic groups of organisms. The concept was introduced by the American zoologist and paleontologist G. G. Simpson (1944). Bradytely is characteristic of certain lamellibranchiate mollusks, which have undergone such insignificant changes in the last 400 million years that contemporary and fossil forms may be classified in the same genus. Simpson erroneously believed that bradytelic forms were unchanging. He believed that the most important factors in bradytely were the presence of numerous freely crossbreeding populations and the specific adaptation of forms to special and permanently existing environmental conditions. The problem of the evolution rate of organisms, and of the factors conditioning it, received original and in-depth treatment in the works of Soviet biologist I. I. Shmal’gauzen.


References in periodicals archive ?
Simpson's inverse: bradytely and the phenomenon of living fossils, pp.