Software development is traditionally conceived as a process where the software development team elaborates, implements and maintains executable models of Information Systems (in the broad sense). In this paper we present an evolutionary view of the software development process, rooted on the General System Theory, which considers software development as a creative process with complex and evolutive interactions between the software development team and the user system. This approach allows to conceive maintenance as a natural projection of an evolutive process. The paper begins considering three different approaches in the conception of Information Systems and our complex view of the relationships between the Information System, the Software System and the Development System. After that it contains a brief survey of previous research on software evolution. It concludes with an exposition of the benefits of our evolutionary approach at the epistemological, methodological and practical level.