Let's avoid the religious debate and assume Evolution is real
The prime drivers of evolution are
1) Random gene mutations
2) Survival of the Fittest/Natural Selection
The issue I see is that humans actively fight against natural selection/survival of the fittest...
We have hospitals where we treat down's syndrome, cancer, epilepsy, and all forms of mental and physical retardation
Without intervention, these "bad genes" would die and leave the gene pool... but, we keep these people alive, to pass on "bad genes" to the next generation
I know it sounds callous, etc., but it seems like a stupid idea to fill the gene pool with "bad genes", rather than let nature take it's course and kill off the poor bastards who drew the short straw
If a dog breeder had a dog with an obvious deformity, it would not use the dog for breeding purposes... that would be stupid to contaminate the breed's gene pool
We're talking here about a change in human environment and habitats which are factors that affect evolution. Specimens that are more suited for their surrounding environment are more successful and desired by the opposite species, therefore they procreate and leave heirs and others that are ill suited for the world don't. In our world it's no longer so necessary to be in a perfect physical condition, it's more desired to be successful in life, therefore the new evolution will favor qualities like entrepreneurship, quick and creative thinking and so on which will eventually become more than just personal qualities that people develop during their life cycle. Human brains will become more and more suited to the demands of this kind of world, while human physique will probably begin to deteriorate.
However our political situation means that this can change in literally hours and we can go from a peaceful world where the threat is that you may lose your job, to a world where you're scavenging for food in the irradiated rubble of a town and fighting for survival is the everyday way of life. An outcome like this will instantly erase the previously well suited branch of newly evolved humans and make physical toughness a prime quality once again.