Evolutionists often claim that evolution is a fact, just like gravity or physics. Below are some quotes of evolutionists admitting that we cannot directly observe the past, which places this type of science into a separate category. Unless otherwise stated, emphasis is mine to help you easily find the important phrases.
What suggestions can we make, what models can we provide, for the development of Earth, Sun, and all the rest of our galactic family? Any hypotheses are tentative and speculative, the events are distant, the evidence indirect, and replication and “proof” are impossible. But there is broad agreement on at least the outlines of a hypothesis. Rhodes, 2012, p. 24
We are at somewhat of a handicap here because, as we know, complex features take a long time to evolve, and most of them did so in the distant past when we weren’t around to see how it happened. Coyne, 2009, p. 136
You can probably see why this argument doesn’t hold water. We’ll never be able to reconstruct how selection created everything–evolution happened before we were on the scene, and some things will always be unknown. But evolutionary biology is like every science: it has mysteries, and many of them get solved, one after the other. Coyne, 2009, p. 137
Even so, artificial selection of real, living creatures–at least creatures bigger than bacteria–is too slow to make an impressive demonstration for impatient and short-lived humans. Dawkins, 1996, p. 30
Rhodes, F. H. (2012). Earth: A Tenant's Manual. Ithaca: Cornell University Press.
Coyne, J. A. (2009). Why Evolution Is True. New York: Viking.
Dawkins, R. (1996). Climbing Mount Improbable. New York: Norton.