So, what is there left to say? Not much. As its title suggests, the fourteenth and final chapter of the origin, ‘Recapitulation and Conclusion’, mostly restates things that Darwin has already said, often several times.
This relentless piling, sorting and re-arranging of evidence can make Darwin seem a little OCD, like an intellectual version of Wall-E. But he also knows that beneath all the case studies, there’s a logical core to evolution by natural selection, even if he can’t put it in an equation. Darwin brackets this chapter by showing that, if you accept the most basic evidence the living world puts before your eyes, evolution follows as surely as a lever moves a stone.
This is from the chapter’s second paragraph:
Nothing at first can appear more difficult to believe than that the more complex organs and instincts should have been perfected not by means superior to, though analogous with, human reason, but by the accumulation of innumerable slight variations, each good for the individual possessor. Nevertheless, this difficulty, though appearing to our imagination insuperably great, cannot be considered real if we admit the following propositions, namely, — that gradations in the perfection of any organ or instinct, which we may consider, either do now exist or could have existed, each good of its kind, — that all organs and instincts are, in ever so slight a degree, variable, — and, lastly, that there is a struggle for existence leading to the preservation of each profitable deviation of structure or instinct. The truth of these propositions cannot, I think, be disputed.
And this is from its final paragraph, amid all the yadda yadda about entangled banks and endless forms most beautiful:
These laws, taken in the largest sense, being Growth with Reproduction; inheritance which is almost implied by reproduction; Variability from the indirect and direct action of the external conditions of life, and from use and disuse; a Ratio of Increase so high as to lead to a Struggle for Life, and as a consequence to Natural Selection, entailing Divergence of Character and the Extinction of less-improved forms.
Between those, like I said, Darwin covers a lot of old ground. But he doesn’t do it in the same order as the rest of the book. First, he revisits the difficulties of his theory, such as sterile castes in social insects and the lack of a continuous record of evolutionary change in the fossil record, which, he says, is “the most obvious and forcible of the many objections which may be urged against my theory”.
These are serious problems. But it’s difficult to know how serious, because they are unknown unknowns:
“I have felt these difficulties far too heavily during many years to doubt their weight. But it deserves especial notice that the more important objections relate to questions on which we are confessedly ignorant; nor do we know how ignorant we are.”
I initially thought it was rather decent of him to list the caveats first. Then I thought it was a characteristically shrewd tactic — let your enemy tire himself out before you make your move, and make sure you leave your readers with the case for, rather than against, freshest in their minds.
Occasionally, though, Darwin makes what seems to be a hopelessly airy assertion. For example, in the midst of yet another page picking at the scab of hybridization, he mentions that “the vigour and fertility of all organic beings are increased by slight changes in their conditions of life”. Really? Sounds to me like all he’s saying is that if we took a holiday, it would be, it would be so nice.
It was at moments like this, which pop up throughout the book, that I most wished I could read the Origin without hindsight. Are the book’s most convincing passages those where Darwin makes his case most skilfully? Or are they just the ones that posterity has treated most kindly? Can’t tell.
It’s worth remembering that evolution didn’t colonize empty ground. There was already a theory for the origin of species, and it needed to be displaced. When Darwin “turn[s] to the other side of the argument”, his writing becomes like a call-and-response. Can we explain it by independent creation? No we can’t!
These are strange relations on the view of each species having been independently created, but are intelligible if all species first existed as varieties.
This grand fact of the grouping of all organic beings seems to me utterly inexplicable on the theory of creation.
How inexplicable on the theory of creation is the occasional appearance of stripes on the shoulder and legs of the several species of the horse-genus and in their hybrids!
On the ordinary view of each species having been independently created, why should the specific characters, or those by which the species of the same genus differ from each other, be more variable than the generic characters in which they all agree?
It is inexplicable on the theory of creation why a part developed in a very unusual manner in any one species of a genus, and therefore, as we may naturally infer, of great importance to the species, should be eminently liable to variation[.]
[T]hese would be strange facts if species have been independently created, and varieties have been produced by secondary laws.
It must be admitted that these facts receive no explanation on the theory of creation.
On the view of each organic being and each separate organ having been specially created, how utterly inexplicable it is that parts, like the teeth in the embryonic calf or like the shrivelled wings under the soldered wing-covers of some beetles, should thus so frequently bear the plain stamp of inutility!
All those sentences appear in a space of nine pages. Darwin could be ruthless when he wanted to. (If you’re wondering about the high frequency of exclamation marks in the passages I’m quoting here, this chapter has a higher !-per-page count than any other in the book except those on the imperfection of the fossil record, the most troubled in the book, and on the struggle for existence, the most vivid.)
Finally, Darwin turns his gaze forward. I’ve tried descent with modification, he says, and I liked it. Why don’t you try it too?
“When we no longer look at an organic being as a savage looks at a ship, as at something wholly beyond his comprehension; when we regard every production of nature as one which has had a history; when we contemplate every complex structure and instinct as the summing up of many contrivances, each useful to the possessor, nearly in the same way as when we look at any great mechanical invention as the summing up of the labour, the experience, the reason, and even the blunders of numerous workmen; when we thus view each organic being, how far more interesting, I speak from experience, will the study of natural history become!”
These last pages contain an even more forceful takeover bid for biology than that in the preceding chapter on classification: “When the views entertained in this volume on the origin of species, or when analogous views are generally admitted, we can dimly foresee that there will be a considerable revolution in natural history.” Follow me, he says, and “the more general departments of natural history will rise greatly in interest” and “a grand and untrodden field of enquiry will be opened”. Famously (but disingenuously, as he’d already solved the problem) “Light will be thrown on the origin of man and his history.”
I’d better give the last word to the man himself. If we can avoid killing those last lines by reading them in hushed and reverent tones, they’re beautiful. I think it’s a mistake to bother much about literary style when discussing science writing, but I particularly like the insertion of “and are being” in the last sentence. It’s a touch of suspense, a flash of weightlessness at the very last moment.
And as the reader lowers the book, it points him or her outward. Evolution isn’t an abstraction, it’s not just something you see on the Galapagos Islands. It’s going on right now, all around you. This is how you see the world now.
“Thus, from the war of nature, from famine and death, the most exalted object which we are capable of conceiving, namely, the production of the higher animals, directly follows. There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.”
Tomorrow! We’ll look back on the whole shebang.