Innovation in normal science. Bacterial physiology.

Abstract

OCIAL HISTORIANS AND HISTORIANS OF IDEAS may not always see eye to eye on the causes of scientific change. Both, however, tend to focus on the most visible evidence of change: dramatic intellectual breakthroughs, formal social organization, or the emergence of research specialties. In turn, most studies of scientific specialties have focused on communication networks, shared theoretical or methodological paradigms, and the formal organization that puts new communities of scientists on the map and keeps them there.1 This is a sensible strategy because large-scale changes in science often seem to occur in rapidly developing but infrequent episodes, a kind of punctuated equilibrium, to borrow a term from recent evolutionary theory. Nevertheless, these macrochanges are exceptional occurrences. Most departures from routine thought and practice are local, small-scale, and evanescent. Even those that do eventually become specialties emerge in isolated contexts after a period of gradual evolution within traditions of science.2 Programmatic visions and formal organization may only consolidate and routinize new ways. But how to write the history of change in normal science, in dispersed groups that have not yet acquired (or may never acquire) grand ideas, group consciousness, and social machinery? A populational approach is one way to explain innovation in normal science. Despite fundamental differences between the social and the natural realms, the language of variation, selection, and isolation should apply to any case of change in loosely connected populations of individuals.3 The trick is to identify, first, the systematic sources of variation in existing communities of science, as well as the inherent limitations on departures from routine, and, second, the exceptional circumstances that in certain local contexts sustain innovation long enough for it to become fashionable. Academic disciplines may well have the greatest systematic influence on vari-