I read Darwin’s: “On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life.”
I found his “The Descent of Man, and Selection in Relation to Sex” largely unreadable.
My understanding of Darwin and neo-Darwinism is that there are mutations and there is selection.
Mutations, as I remember, are little more than birth defects, or failures to replicate properly for whatever reason. Birth defects seem like an unlikely path forward. Even extreme Darwinian environmentalists don’t seem to favor swimming by nuclear reactors. How else are we going to get X-men (fictional superheroes)?
Natural selection seems plausible enough, but I view it as a conservative mechanism. Three legged dear and myopic eagles are likely to be selected out. Darwin got his idea of natural selection, at least in part, from artificial selection, otherwise known as breeding. We breed cattle, dogs, cats, horses, etc with considerable effect. Artificial selection is more powerful and rapid than natural selection.
However, there are limits to selection. We cannot breed a horse to have wings as you say. The material just isn’t there in the gene pool. Happy accidents, such as might be induced by irradiating testicles and eggs, are unlikely to bring about the necessary changes, no matter how well you breed any surviving offspring.
Mutations are going to happen in any case. That can't be stopped. Our natural environment is simply rife with mutagenic factors (cosmic rays, etc.)
And no biologists worth his or her salt would ever claim that any but a tiny minority of mutations are beneficial.
However, for natural selection / evolution to take place, that doesn't matter.
99.99% of the mutations will assuredly be negative. But if 0.01% are beneficial, the corresponding trait will persist and establish itself.
Is that so hard to understand?
Have no idea what you mean by "no matter how well you breed any surviving offspring." This is about NATURAL selection.
Regards,