For example, 10 000 years ago, imperfect vision, say short sightedness, is a very bad omen for a boy-child whose destiny is to become a hunter.
But maybe this child, instead of going hunting, will survive by inventing herding or agricultural techniques.
So if you consider farming and herding an evolutionary step over hunting, then perhaps this step was made by a short sighted riff raff boy, rather than by the good looking male hunters (with lots of children) of the clan.
'What doesn't kill you makes you stronger' would say the riff raff.
Correct, this means that 'Evolution' and 'Fitness/Survival' are not the same thing.
There is a general and widespread misunderstanding of the evolutionary biology concept of 'fitness'. Simply stated, 'fitness' is the number of viable offspring and individual produces (it can be expressed in absolute or relative terms, and can apply to complete organisms or genes)
One can even consider that 'Evolution' is a risky business which may have no great positive impact on the population numbers, at least initially. Then when the evolutionary changes have settle, the population growths again, but this time with no appreciable change (Gould stasis).
One can even goes further. In a model where the fluctuations of the characteristics of a species are just that: the fluctuations around an average and general species stereotype (Gould again, said that), these fluctuations are not considered as 'evolutionary changes' per se. Which means that Natural Selection, which nevertheless never stops acting in this fluctuating population, does not drive evolution anywhere here. Therefore Natural Selection might not be the Deus ex machina of Evolution, at least not as described by the Darwinian supporters.
For anything, Natural Selection should even be a brake to evolutionary change. It's role should be only to keep things fit, but un-changed, that is, Natural selection should stop evolution rather than drive it.
And that's totally consistent with this paper we discussed a few month ago. 'Evolution' was reframed with Information Theory concepts. Natural Selection was just a filter of entropic decay, it was not driving the complexity of the virtual organisms up, properties in the algorithmic complexity of the digital organisms was.
Now if Natural selection is just one filter, then un-natural selection is also a filter. What would be the fate of digital virtual organisms if medicine for the unfit was applied to them?
Darwinian who pose Natural Selection as the required Deus ex machina should predict an evolutionary stall, since Natural Selection is removed. They have to be consistent with their own theory: 'descendant with modification and survival of the fittest', when nobody, or everybody is the fittest, can only increase population numbers, but cannot drive Evolution.
But if Natural Selection is merely a filter, and one that can even slow down the trend in increased complexity, then the relaxation of a very stringent selection will have the opposite effect: accelerated Evolution.