Darwin's Readings Of The Process Of Evolution
( Originally Published Early 1900's )
"This is the doctrine of Malthus applied to the whole animal and vegetable kingdom. As many more individuals of each species are born than can possibly survive ; and as, consequently, there is a frequently recurring struggle for existence, it follows that any being, if it vary however slightly in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have a better chance of surviving, and thus be naturally selected. From the strong principle of inheritance, any selected variety will tend to propagate its new and modified form.
"I am fully convinced that species are not immutable; but that those belonging to what are called the same genera are lineal descendants of some other and generally extinct species, in the saine manner as the acknowledged varieties of any one species are the descendants of that species. Furthermore, I am convinced that natural selection has been the most important, but not the exclusive, means of modification."
—Quoted from the Introduction to Origin of Species.
"According to the theory of natural selection, an inter-minable number of intermediate forms must have existed, linking together all the species in each group by gradations as fine as our existing varieties.
"As natural selection acts solely by accumulating slight, successive favorable variations, it can produce no great or sudden modifications. It can act only by short and slow steps.
"There is grandeur in this view of life, with its several powers, having been originally breathed by the Creator into a few forms or into one; and that, while this planet has gone circling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been evolved."
—Quoted from the Recapitulation of Origin of Species.
"Professor Huxley, in the opinion of most competent judges, has conclusively shown that in every visible character man differs less from the higher apes than these do from the lower members of the same order of Primates."
—Quoted from the Introduction to Descent of Man.
"By considering the embryological structure of man,—the homologies which he presents with the lower animals,—the rudiments which he retains,—and the reversions to which he is liable, we can partly recall in imagination the former condition of our early progenitors; and can approximately place them in their proper place in the zoological series. We thus learn that man is descended from a hairy, tailed quadruped, probably arboreal in its habits, and an inhabitant of the Old World.
"The high standard of our intellectual powers and moral disposition is the greatest difficulty which presents itself after we have been driven to this conclusion on the origin of man. But every one who admits the principle of evolution, must see that the mental powers of the higher animals, which are the same in kind with those of man, though so different in degree, are capable of advancement. Thus, the interval between the mental powers of one of the higher apes and of a fish, or between those of an ant and a scale-insect, is immense ; yet their development does not offer any special difficulty ; for with our domesticated animals, the mental faculties are certainly variable, and the variations are inherited. No one doubts that they are of the utmost importance to animals in a state of nature. There-fore the conditions are favorable for their development through natural selection. The same conclusion may be extended to man."
—Quoted from General Summary of Descent of Man.