Darwin put fort the notion of the survival of the fittest. How do we define 'fittest'? The answer usually given is those who survive. So you can readily see that this is a circular agrument and doesn't really help us understand what really happens following natural selection quite clearly. The idea of fitness as a matter of survival will not do. Therefore in the course of the development of what we have earlier referred to as the modern synthesis the notion of fitness was related to the ability of the individual to maximise the number of progeny left in the next generation. In other words the notion of fitness was translated into reproductive success. Given the idea of fitness as being measurable in terms of reproductive success we can now go back to basic tenets of Darwinism. The first of the five observations mentioned therein was the tendency on the part of living organisms to reproduce: In an exponential manner. We noted that the consequence of this is competition for available resources which results in "the survival of the fittest" Clearly, therefore. in3terms of reproductive ability nature is truly prodigal.