Abstract

The increasing place of evolutionary scenarios in functional biology is one of the major indicators of the present encounter between evolutionary biology and functional biology (such as physiology, biochemistry and molecular biology), the two branches of biology which remained separated throughout the twentieth century. Evolutionary scenarios were not absent from functional biology, but their places were limited, and they did not generate research programs. I compare two examples of these past scenarios with two present-day ones. At least three characteristics distinguish present and past efforts: An excellent description of the systems under study, a rigorous use of the evolutionary models, and the possibility to experimentally test the evolutionary scenarios. These three criteria allow us to distinguish the domains in which the encounter is likely to be fruitful, and those where the obstacles to be overcome are high and in which the proposed scenarios have to be considered with considerable circumspection