What is Darwin’s point in chapter 14?
In this chapter, Darwin concludes the book and briefly reviews things stated earlier.
At the beginning of the chapter, he claims to have given arguments against his theory their “full force”.
“That many and grave objections may be advanced against the theory of descent with modification through natural selection, I do not deny. I have endeavoured to give to them their full force.”
One objection he notes is the lack of evidence of gradations of life in the fossil record.
“On this doctrine of the extermination of an infinitude of connecting links, between the living and extinct inhabitants of the world, and at each successive period between the extinct and still older species, why is not every geological formation charged with such links? Why does not every collection of fossil remains afford plain evidence of the gradation and mutation of the forms of life? We meet with no such evidence, and this is the most obvious and forcible of the many objections which may be urged against my theory.”
And he counters this by saying “I can answer these questions and grave objections only on the supposition that the geological record is far more imperfect than most geologists believe.”
I would not consider his response to be of much force. And if we are to apply scientific standards to this argument, it would have no force. The scientific response would first be to question the theory, not to question the data.
He mentions an idea that I feel is probably more closer to actuality than his theory.
“It has often been asserted, but the assertion is quite incapable of proof, that the amount of variation under nature is a strictly limited quantity.”
It might be incapable of proof, but the evidence for it would be much stronger than unlimited capability of variation. We see this especially with domesticated organisms. Plants and animals can undergo various physical changes through selective breeding. But there is a limit to what can be achieved. Pretty much a dog is still a dog. Or an apple is still an apple. So, in terms of evidence, it would support limited changes, rather than unlimited changes.
Near the final pages of the book, he mentions how far natural selection can be inferred.
“It may be asked how far I extend the doctrine of the modification of species. The question is difficult to answer, because the more distinct the forms are which we may consider, by so much the arguments fall away in force.”
“Therefore I cannot doubt that the theory of descent with modification embraces all the members of the same class. I believe that animals have descended from at most only four or five progenitors, and plants from an equal or lesser number.”
“Therefore I should infer from analogy that probably all the organic beings which have ever lived on this earth have descended from some one primordial form, into which life was first breathed.”
So, the book does not spend any notable length of time in arguing that all life descended from a handful of lifeforms. He only mentions this in only two paragraphs of the final chapter.
I believe that the evidence to support the theory of natural selection only applies to the very lowest levels of the Linnaean taxonomy. And this would be in agreement with “that the amount of variation under nature is a strictly limited quantity.”
Though I believe this is what the evidence supports, making such a statement would not have much of an impact since it would be largely self-evident. But, to make the inference that all of life is from a common ancestor would make a significant impact. Darwin realizes this and also notes that it would impact other disciplines.
“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.”
“Psychology will be based on a new foundation, that of the necessary acquirement of each mental power and capacity by gradation. Light will be thrown on the origin of man and his history.”
Throughout the book, he also fails to define what is species. And I think he should have given some sort of definition since it is used in the title of the book. But, rather than trying to give a clearer view of what species is, he makes it even more blurred at the end.
“In short, we shall have to treat species in the same manner as those naturalists treat genera, who admit that genera are merely artificial combinations made for convenience. This may not be a cheering prospect; but we shall at least be freed from the vain search for the undiscovered and undiscoverable essence of the term species.”
But, if species then becomes undefined and undiscoverable, any claim on how species originate would itself be a vain attempt.
In the entire book, I did not see any reference stating that God does not exist. Though God might not have been involved in creating life, Darwin states that God could have setup the natural laws for life.
“To my mind it accords better with what we know of the laws impressed on matter by the Creator, that the production and extinction of the past and present inhabitants of the world should have been due to secondary causes, like those determining the birth and death of the individual.”
I find it interesting that he never uses the word “evolution” in the book. And that the only time the word “evolve” is found is at the very last word of the book.
Some final comments on the book. Though the book has brought about a revolution in thinking in history, I doubt that very many people have read through this book. Though many people refer back to this book, I doubt those who do can state what Darwin argues in the book. And now that I’ve read through the book, it’s a wonder to me how so many people in history have been affected by this work. I do not think it’s been influential because of the persuasiveness of the evidence and arguments. But it is influential because people want to believe in it. And those who want to believe in it do not give it much of a critical eye. Rather, they want to hear any justification, no matter how weak it is, that there is a glimmer of any rational basis to what they want to believe.