'without the variations, natural selection has nothing to act on.'
Darwin is clearly correct on this point. Its too bad that he allowed his imagination and prior commitment to anti-creationism to allow him to build a fantasy origins theory on such inadequate foundations as the minor cyclical variation he observed in dogs, finches and pigeons. Of course, he knew nothing of DNA, but we do, so have even less excuse for attributing the variations to unguided processes.
That natural selection cannot do a thing unless there are variant forms for it to choose between is obvious and undeniable. That Darwin knew this is clear, for he wrote it. So (setting aside the origin of life, as evolutionists usually do) its the origin of the variations that really take us to the crux of the matter. But where do the variations that turned mice into men, fish into reptiles, pond scum into insects, come from? How do they arise? The visible form of the animal that we see (the phenotype) depends on the precise information in the DNA (the genotype).
Anyway, here's some hard science facts about random DNA variations- real, not imaginary.
This item brings us up to date with the latest science developments in understanding and treating the deadly malignant melanoma skin cancer. This dreaded cancer is curable if diagosed and removed early, but once it spreads to internal organs it tends to be fatal.
What causes melanoma? DNA mutations, as the linked item and many others that can be Googled (try melanoma + mutations). Melanoma is particularly rich in mutations, including the BRAF mutation. Sophisticated, intelligently designed, drugs like Yervoy (TM) have been developed to attack the mutated melanoma cells, and there have been some remarkable successes (Google Yervoy) but the cancer usually wins in the end (search Google images on melanoma for some horrible images of people dying from this awful disease). How does melanoma cancer 'adapt' to beat the tailored drugs that initially beat it back? Natural selection of clones of mutated cancer cells that are naturally unffected by the drug. The anti cancer drugs knock out some mutant clones, but other mutant clones unaffected by the drug move into their ecological niche and eventually overwhelm the patient's defences. Some variations of melanoma cells are more fit in the sense that Yervoy doesn't kill them, its rather similar to the biology of antibiotic resistance. I won't repeat here what I've already said on that subject.
Cancer cells have lost the information that causes them to behave in an orderly manner, they are basically rebel cells gone wild. This knowledge should cause us to ponder-why do cells usually behave normally? The answer, and this is not contentious, is that they contain high level precise, constrained DNA information which issues commands that tell cells how to behave. When this control centre is disabled by a random mutation, you get the loss of control which is cancer. Cells stop obeying proper commands and go wild, doing their own thing, mindlessly oblivious to the fact that they too will die when they kill the host that sustains them. I will resist for now the temptation to apply this principle to order versus anarchy in human individuals and societies that reject proper authority. Plenty of examples of that in the news.
Mutations are basically scrambled DNA, as the linked article mentions. When you randomly re-arrange orderly information sequences, whether computer code, construction blueprints, travel directions, or DNA, you tend to mess things up. As we observe in nature. Stephen Meyer writing in his book 'Signature in the Cell' corrrectly notes that orderly, meaningful, information sequences are only ever observed to come from deliberate effort from an intelligent source. Since DNA is the highest level of precise, meaningful information in the known universe, isn't it reasonable to assume it was designed? No, we are told, because that might imply God, which is axiomatically ruled out.
But aren't DNA mutations the building blocks which we are told created the variations which Natural Selection acted on to take us from amoeba to man. Yup, that's right. there is no other available mechanism to create the variations necesary for neo-Darwinian evolution other than random mutation. That's the theory, but what's the reality? Melanoma, among other results of naturally occuring random mutations, is the reality. Mutation wrecks functional DNA, it does not create it. This is exactly what Intelligent Design Theory predicts. It is the opposite of what Darwinian Evolutionism requires to be true.
As Cornell geneticist John Sanford explains in his book 'Genetic Entropy: the Mystery of the Genome' even if there were occasional information-adding 'beneficial' mutations, they would be overwhelmed by the great majority of mutations which are 'near neutral' or actively harmful. But no mutation has ever been observed to create a new piece of specified and beneficial information. Michael Behe in his book 'Edge of Evolution' demonstrates that the tiny number of 'beneficial' mutations (e.g. antibiotic resistance, sickle cell disease) are due to 'broken and blunted genes' which give limited situational benefit due to loss of information. They don't create anything new.
Mutations destroy, they do not build. Science fact. That's the reality which evolutionists must deny.