“Evolution” in its deepest sense is a foundational metaphysical commitment, not a scientific theory that one could test. One can see this clearly by looking into Darwin’s notebooks, from his most creative period as a theorist (1837-42). Consider, for instance, the following rhapsodic passage, from Darwin’s D Notebook; the emphases are mine:
16th Aug. What a magnificent view one can take of the world Astronomical & unknown causes modified by unknown ones, cause changes in geography & changes of climate suspended to change of climate from physical causes, — then suspended changes of form in the organic world, as adaptation, & these changing affect each other, & their bodies by certain laws of harmony keep perfect in these themselves. — instincts alter, reason is formed & the world peopled with myriads of distinct forms from a period short of eternity to the present time, to the future. — How far grander than idea from cramped imagination that God created (warring against those very laws he established in all organic nature) the Rhinoceros of Java & Sumatra, that since the time of the Silurian he has made a long succession of vile molluscous animals. How beneath the dignity of him, who is supposed to have said let there be light & there was light. — whom it has been declared “he said let there be light & there was light”
In no sense is this a scientific hypothesis. It is, rather, a vision of a materialistic narrative-to-be, one that will be “magnificent,” “grander,” and befitting the “dignity” of the Creator. “Unknown causes,” used twice by Darwin, stand in for evidence, as do “certain laws of harmony,” whatever those might turn out to be.
“No Detectable Design”
Darwin knows what he wants: the formulation of natural selection lies in the future. And, after 1859, when natural selection takes a battering at the hands of Darwin’s critics, and is treated with indifference or even hostility by his main lieutenant, T.H. Huxley, Darwin does not retreat from his commitment to his original materialistic vision. He modifies the theory in the sixth edition of the Origin by greatly increasing the causal role of “use and disuse.”
We need to take seriously the probability that “evolution” mostly means “no detectable design.” If that’s so, then it may be a fool’s errand to try to test “evolution.” One cannot overturn a metaphysical commitment by evidence, because that commitment wasn’t arrived at via evidence.
Image: “The Wanderer Above the Sea of Fog,” c. 1817, by Caspar David Friedrich, via Wikimedia Commons.