Is evolution wandering through the vast space of adaptation to countless habitats, or is it moving on "rails" created by numerous constraints? The model of evolution on rails is tempting, since it provokes expectancies as to the possibility of creating a theoretical biology by analogy to physics, chemistr or other natural sciences. If evolution proceeds in definite directions, it seems possible to reveal formulas and laws in it. The attempts to substantiate the idea of “directionality” of evolution are not limited to the last 150 years. Are they meaningless or promising? To answer this question I will survey the arguments in favor of this model in a historical perspective.
Igor Popov studied zoology at Saint-Petersburg State University, Russia. His earliest work was on the ecology and taxonomy of bats, and the ecology of flying squirrels and some other rodents. From 1993 to 2003 he worked at the Institute for the History of Natural Sciences and Technology, Russian Academy of Sciences. His PhD thesis (1998) was devoted to the history of studies of geographical variability and the formation of the evolutionary synthesis. Since 1998 he has been dealing mainly with the history of non-Darwinian evolutionary concepts and the history of the attempts to create a “periodical system of elements” in biology. Since 1995 he also works at the Institute for Lake and River Fisheries (Saint-Petersburg), where he is involved in various studies of Salmonid fishes. Dr. Popov's current research is devoted to the idea of directed evolution.