This paper introduces ATNoSFERES, a model aimed at designing evolutive and adaptive behaviors for agents or multi-agent systems. We first discuss briefly the main problems raised by classical evolutionary models, which are not intended to produce agents or behaviors but to solve problems. Then we provide detailed explanations about the model we propose and its components. We also show through a simple example how the system works, and give some experimental results. Finally, we discuss the features of our model and propose extensions.