Specific chemical resemblances of closely related forms; e. g., blood tests.
Fourth—Evidence from experimentation rests upon:
Unconscious experimentation upon animals and plants since their domestication.
Conscious experimentation of breeders and of scientific investigators.
The nature of these lines of evidence may now be indicated.
Evidence From Comparative Anatomy—In the animal kingdom as a whole and in every group of animals, whether large or small, we find facts that may be interpreted most reasonably in terms of evolution. The vertebrates or backboned animals will serve as an illustration. We find here a certain plan of structure, for example, backbone, two pairs of limbs, body, head and various internal organs, all laid down according to a similar general plan, but with endless modifications to suit the mode of life. The flipper of a whale, the wing of a bird or a bat, the forefoot of a horse, the arm of a man, and the like, all show the same plan of structure. One of the pre-Darwin ideas was that each animal, while created separately, was nevertheless formed in accordance with a certain type that the Creator had in mind, hence the resemblance. Such an idea is a theoretical possibility, provided there is any evidence to show that animals were created all at once and separately, But there is not a shred of such evidence that will appeal to one who approaches the matter with an open mind and uninfiuenced by preconceived notions.
On the other hand, the biological explanation of this anatomical resemblance is that the present vertebrates (fishes amphibia, reptiles, birds and mammals) have all descended from a primitive race, somewhat like the present fishes. All vertebrates are now alike, because they have never lost the underlying plan of structure inherited from their common ancestry. They have come honestly and naturally by present organization.
The Evidence From Fossils—(Paleontology) Interlocks with the above, since the first vertebrates known to appear were primitive fish-like forms. These were succeeded by amphibians, reptiles, mammals and birds in the order named, the last two having connecting links with the reptiles. The invertebrate groups fell a similar story.
Turning to the Facts of Comparative Embryology—The kind of evidence everywhere discoverable may be illustrated by the gill-slits in the embryos of higher vertebrates like reptiles, birds and mammals. All these forms exhibit in their early stages of development a fish-like plan of structure, particularly in the neck region where the gill-slits are located. The reasonable interpretation of the existence of such structures in the embryo of a human being, or any land-living vertebrate, is that we have never lost these telltale evidences of our ancestry. The later stages of our development are modified so that they lead to the adult human body. The earlier stages still show the primitive conditions of a fish-like organization. Modern fishes have survived to the present day without a fundamental departure from the ancestral condition, Modern amphibia (frogs, toads and salamanders) have survived in the halfway state between an aquatic and a terrestrial existence, through which higher vertebrates have passed as indicated by the fossil record and by the above fish-like stages in their development.
The facts of classification are commonly cited as evidence for evolution. Since classification is based on structure (anatomy), this is but an aspect of the general evidence from comparative anatomy and embryology. While the facts cannot be detailed here, they are striking and bear out the doctrine.
Another line of evidence is that of geological geographical distribution. The facts in this connection are utterly senseless and insulting to an intelligent Creator, if viewed
