I understand that in each generation of a genetic algorithm, that generation must re-prove it's fitness (and then the fittest of that population is taken for the next population).
In this case, I guess it's a presumption that if you take the fittest of each generation, and use them to form the basis of the next generation, that your population as a whole is getting fitter with time.
But algorithmically, how can I detect this? If there's no end goal known, then I can't measure the error/distance from goal? So how can you tell how much each generation is becoming fitter by?