The Essence of Darwinism and the Basis of Modern Orthodoxy 105
The Origin of Species presents an ingenious compendium of all four methods.UNIFORMITY. People who do not understand science in their bones, and who
think that revolutionary treatises must be presented as ideological manifestos at
broadest scale, often express surprise and disappointment in reading the Origin,
especially at Darwin's opening chapter. They expect fanfare, and they get
fantails—pigeons, that is. But Darwin ordered his book by conscious intent and
strategy. He knew that he had to demonstrate evolution with data, not simply
proclaim his new view of life by rhetoric. Uniformitarianism embodied his best
method based on maximal information—so he started from the smallest scale,
change in domestication, and worked up to the history of life. As a member of two
London pigeon fancying clubs (which he had joined, not from an abiding affection
for this scourge of cities, but to gain practical information about evolution in the
small), Darwin led from his acquired strength.
What better starting point, under method 1, than indubitable proof of
historical change in domesticated plants and animals. The logic of the Origin
employs one long analogy between artificial and natural selection, with uniformity
as the joining point. Darwin writes in his introduction (p. 4): "At the
commencement of my observations it seemed to me probable that a careful study
of domesticated animals and of cultivated plants would offer the best chance of
making out this obscure problem. Nor have I been disappointed; in this and in all
other perplexing cases I have invariably found that our knowledge, imperfect
though it be, of variation under domestication, afforded the best and safest clue."
Darwin continually drives home this analogy and extrapolation: if by artificial
selection at small scale (as we know for certain), why not by natural selection at
larger scale: "If it profit a plant to have its seeds more and more widely
disseminated by the wind, I can see no greater difficulty in this being effected
through natural selection, than in the cotton-planter increasing and improving by
selection the down in the pods on his cotton-trees" (p. 86).
But this argument by uniformitarian extrapolation presents a serious difficulty
(exploited by Fleeming Jenkin, 1867, in the famous critique that Darwin ranked so
highly, and took so seriously in revising the Origin): change surely occurs in
domestication, but suppose that species function like glass spheres with a modal
configuration at the center and unbridgeable limits to variation representing the
surface. Artificial selection could then bring morphology from the center to the
surface, but no further—and the key argument for smooth extrapolation to all
change over any time would fail. Darwin therefore staked a verbal claim for no
limit. "What limit can be put to this power, acting during long ages and rigidly
scrutinizing the whole constitution, structure, and habits of each creature—
favoring the good and rejecting the bad? I can see no limit to this power, in slowly
and beautifully adapting each form to the most complex relations of life" (p. 469).
Darwin then applied the full sequence of extrapolation to the natural