The 4 Cs of evolutionary explanation
Evolution is defined as change through time, and occurs, in a Darwinian framework, because of the force of natural selection. This is the CAUSE of evolutionary change. However, other processes are important. Selection operates in particular contexts and environments, and the the outcomes will be very dependent upon the CONDITIONS. Furthermore, natural selection is not all powerful – it cannot create the impossible, and so there are CONSTRAINTS (physical, historical, etc.). Finally each evolutionary change has CONSEQUENCES which will in turn change the CONDITIONS of selection.