"Recapitulation and Conclusion" is the fourteenth and last chapter of On the Origin of Species by Means of Natural Selection by Charles Darwin. In this chapter, Darwin quickly sums up all of the theories of evolution, and arguments for and against them, that he has explored throughout the book. Darwin begins the chapter by writing about the strangeness of his theory. "Nothing at first can appear more difficult to believe," he writes, "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," he continues, "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."
Darwin then moves on to other thoughts about his theories. Why, for instance, are we not surrounded by closely and gradually related plants and animals, instead of distinct species? "Why are not all organic beings blended together in an inextricable chaos?" Darwin’s main argument here is that we should not expect to find beings directly related, but only related through a distant ancestor, and that we should not expect to find this ancestor still living, because its descendants will have caused its extinction through their greater success in the struggle for existence.
Darwin mentions again that his theory is dependent in part on the geological record being imperfect and incomplete, and that "[t]he number of specimens in all our museums is absolutely as nothing compared with the countless generations of countless species which certainly have existed." Indeed, we should expect to never find fossil remains of most of these species, "for fossiliferous formations, thick enough to resist future degradation, can be accumulated only where much sediment is deposited on the subsiding bed of the sea." During periods between these occurrences, the fossil record is blank.
In the next section of this chapter, Darwin comes back to variation under domestication, which he discussed at the beginning of his book. Here he has an interesting statement about domestication. "Man does not actually produce variability," he writes, "he only unintentionally exposes organic beings to new conditions of life, and then nature acts on the organisation, and causes variability. But man can and does select the variations given to him by nature, and thus accumulate them in any desired manner." The idea that humanity cannot produce variation is even more fascinating now than it was it Darwin’s time, because it is no longer true. Michael Pollan writes about genetic engineering in his book The Botany of Desire. He begins by quoting Darwin that "[m]an does not actually produce variability," then continues with his own response. "Now he does," Pollan writes. "For the first time, breeders can bring qualities at will from anywhere in nature into the genome of a plant: from fireflies (the quality of luminescence), from flounders (frost tolerance), from viruses (disease resistance), and, in the case of my potatoes, from the soil bacterium known as Bacillus thuringiensis.” Our attempts to breed plants and animals for our benefit are, for better or worse, no longer shackled by Darwinian evolution and modification by descent.
Coming back to Darwin’s writing, at this point in his last chapter he moves on to discussing specific problems in biology that his theories solve. For instance, they let us "see why it is that no line of demarcation can be drawn between species," he writes, because "each species first existed as a variety." Darwin’s theories also predict that species will tend to increase in number and diverge in character, and Darwin writes that this, "together with the almost inevitable contingency of much extinction, explains the arrangement of all the forms of life, in groups subordinate to groups, all within a few great classes, which we now see everywhere around us, and which has prevailed throughout all time. This grand fact of the grouping of all organic beings seems to me utterly inexplicable on the theory of creation."
Darwin also writes that we should not "marvel if all the contrivances in nature be not, as far as we can judge, absolutely perfect; and if some of them be abhorrent to our ideas of fitness." For instance, the death of a bee upon use of its stinger should not shock us, because in the context of evolution it makes sense. And, if species are merely "well-marked and permanent varieties," then hybridism, and the ability of species to interbreed to some degree, suddenly makes sense. These theories also explain why many oceanic islands are inhabited by no mammals except the bat, why some organs are better than others for determining the relationships between species, and why the skeletons of such animals as the bat, porpoise, and horse are so similar.
But, despite all the phenomena evolution explains, in Darwin’s time, as in ours, many rejected it. Darwin addresses this issue in his conclusion as well, and writes that "[i]t cannot be asserted that organic beings in a state of nature are subject to no variation; it cannot be proved that the amount of variation in the course of long ages is a limited quantity; no clear distinction has been, or can be, drawn between species and well-marked varieties. It cannot be maintained that species when intercrossed are invariably sterile, and varieties invariably fertile; or that sterility is a special endowment and sign of creation. The belief that species were immutable productions was almost unavoidable as long as the history of the world was thought to be of short duration." But why is there this difficulty now? Darwin writes that people simply have a hard time adjusting to the idea that change can take take place over great periods of time, in ways so slow that they are barely noticeable within our lifetimes. "The difficulty is the same felt by so many geologists," he writes.
This difficulty is so great, Darwin continues, that he does not expect many naturalists of his generation to agree with him. "I look with confidence to the future," he writes, "to young and rising naturalists, who will be able to view both sides of the question with impartiality."
If his theories succeed, Darwin speculates, biology will go through major changes. The relevance of distinctions between species will decrease, and the concept will be viewed merely as an arbitrary convenience. The terms used by biologists to describe relationships between species will become literal, and not merely metaphors. Classifications will morph into genealogies. Geology will be seen as much less perfect than thought, and perhaps lose some nobility. History will be seen as much longer than thought, and perhaps gain some majesty. Psychology and the history of humanity will be reexamined.
Indeed, many of these things have happened. The theory of evolution by means of natural selection, and other related theories, have become some of the most important ideas in the world today. But to me, the last paragraph of Origin of Species is the most fascinating. It is a paragraph that the late Stephen Jay Gould quoted frequently, as it sums up not just why evolution is a fact, not just why evolution is true, but why evolution doesn’t take away anything from the glory of nature, and most of all, why evolution is a really cool idea.
"It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us. 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. 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."
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