For those scientists who take it seriously, Darwinian evolution has functioned more as a philosophical belief system than as a testable scientific hypothesis. This quasi-religious function of the theory is, I think, what lies behind many of the extreme statements that you have doubtless encountered from some scientists opposing any critical analysis of neo-Darwinism in the classroom. It is also why many scientists make public statements about the theory that they would not defend privately to other scientists like me.
The phrase 'the fossil record' sounds impressive and authoritative. As used by some persons it becomes, as intended, intimidating, taking on the aura of esoteric truth as expounded by an elite class of specialists. But what is it, really, this fossil record? Only data in search of interpretation. All claims to the contrary that I know, and I know of several, are so much superstition.
I recently asked more than seventy eminent researchers if they would have done I their work differently if they had thought Darwin's theory was wrong. The responses were all the same: no. I also examined the outstanding biodiscoveries of the past century: the discovery of the double helix; the characterization of the ribosome: the mapping of genomes; research on medications and drug reactions: improvements in food production and sanitation; the development of new surgeries; and others. I even queried biologists working in areas where one would expect the Darwinian paradigm to have most benefited research, such as the emergence of resistance to antibiotics and pesticides. Here, as elsewhere, I found that Darwin's theory had provided no discernible guidance, but was brought in, after the breakthroughs, as an interesting narrative gloss.
Throughout 150 years of the science of bacteriology, there is no evidence that one species of bacteria has changed into another.. Since there is no evidence for species changes between the simplest forms of unicellular life, it is not surprising that there is no evidence for evolution from prokaryotic [i.e., bacterial] to eukaryotic [i.e., plant and animal] cells, let alone throughout the whole array of higher multicellular organisms.
I am absolutely convinced of the lack of true scientific evidence in favour of Darwinian dogma. Nobody in the biological sciences, medicine included, needs Darwinism at all. Darwinism is certainly needed, however, in order to pose as a philosopher, since it is primarily a worldview. And an awful one, as George Bernard Shaw used to say.
All disciplines of science are built on the causality of the relationships governing related events. Yet the theory of evolution is built upon the idea of accidental changes that resulted in complex living systems. I was unable to comprehend how the notion that an infinite number of random accidents systematically happened to produce living species, and kept improving these beings, is justified.