Genetics has determined that humans do no diverge by more then a fraction of a percent of their DNA. Mendelian genetics has all but vanquished race and the Darwinian concept of multiple species and subspecies of humans.
That's very true and all too often actual biology is irrelevant to what's being discussed. When you can't get basic biological facts like the molecular basis for adaptive evolution agreed to any discussion of Biology and Genetics is destined to drift into the stacks.
The age of the earth is irrelevant to the doctrine of creation and I can demonstrate that from an exposition of Genesis 1. The origin of life on this planet is another story entirely.
Greater lengths of time do not give you an established molecular mechanism for the overhaul of highly conserved genes. Brain related genes in particular.
I don't think anyone could deny that there are clear limits. Functional constraint, the deleterious effects of mutations and just the fidelity of the DNA replication process argue strongly for obvious limits.
Darwin was reading Lyell while on board the Beagle, he often discusses at length. Gradualism is quite simply the gradual accumulation of traits changing over time. The influence of Lyell on his think cannot be overestimated.
Most Christians wouldn't have even been aware of Catastrophism. A straight forward exposition of the time line in the Old Testament then, just as now, was sufficient.
Darwinian naturalism became very popular and it was developed philosophically with the help of philosophers like Asa Grey and Hebert Spencer. Mendel had discovered that traits emerged in cyclical patterns something Darwin would have known simply as varieties. Mendel noted a prevailing stability, aka stasis, and that, 'species are fixed within limits beyond which they cannot change.' (Mendel, Experiments in plant-hybridisation 1865). Evolution is defined in Biology by genetics. Darwinism was a part of a much larger philosophy that could be understood better as Naturalism and was developed by guys like Asa Grey, Darwin's philosophical pen pal and Herbert Spencer. Spencer related the concept of natural selection to political and legal theory, thus, the advent of Social Darwinism.
Darwinism is much more then the theory of natural selection, it's also a legal and social theory. In the post WW2 world Soviet Russia and China rejected Mendelian Genetics as being an unhealthy western influence while Darwinism was embraced whole heartily:
Three generations of imbeciles are enough." This decision opened the floodgates for thousands to be coercively sterilized or otherwise persecuted as subhuman. Years later, the Nazis at the Nuremberg trials quoted Holmes's words in their own defense...In Mein Kampf, published in 1924, Hitler quoted American eugenic ideology and openly displayed a thorough knowledge of American eugenics. "There is today one state," wrote Hitler, "in which at least weak beginnings toward a better conception [of immigration] are noticeable. Of course, it is not our model German Republic, but the United States."
HNN article
The Theory of Evolution has become synonymous with Darwinian thinking through the Modern Synthesis. I didn't coin the term and it's not something exclusive to Creationist thinking. I will not forego the use of it when discerning between the phenomenon of adaptive evolution and the apriori assumption of universal common descent by exclusively naturalistic means.
There is a rich history there, completely unaffected by Darwinism.
Darwin could not have even conceived of chromosomes let alone DNA and certainly wouldn't have had any concept of genes. Mendel simply refereed to them as 'elementals' since the substance of the molecular basis was completely unknown. Mendelian Genetics went through a process culminating in the DNA double helix model to be recognized as science, there are two foundation laws of science and a growing body of research involved. Darwinism enjoyed over night success without contributing much in practical terms to real world science. Mendelian Genetics has never been accused of being responsible for inciting racist thinking and to date I have yet to see it so much as criticized for it's social, legal or political implications. You just can't say that about Darwinism.
I think if you dismiss Darwinism, the controversy over evolution goes away, Mendelian Genetics never needed it. When it comes to teaching evolution the only question that merits serious attention is how the central term 'evolution' is defined scientifically. Do we insist on Lamarck's prescription or simply defer to what can be directly observed or demonstrated. Opinions vary but Darwinian thinking transcends the boundaries of natural science into political, social and legal agendas.