THE EVOLUTION OF BRICOLAGE

The past ten years of developmental genetics have revealed that most o f our genes are shared by other species throughout the animal kingdom. Consequently, animal diversity might largely rely on the differential use of the same components, either at the individual level through di vergent functional recruitment, or at a more integrated level, through the participation in various genetic networks. Here, we argue that th is inevitably leads to an increase in the interdependency between func tions that, in turn, influences the degree to which novel variations c an be tolerated. In this 'transitionist' scheme, evolution is neither inherently gradualist nor punctuated but, instead progresses from one extreme to the other, together with the increased complexity of organi sms.