THE ASCENT OF MAN.

Being a Summary of Charles Darwin’s “ Descent of Man.”

S U P P L E M E N T TO “ T H E L I T E R A R Y G U I D E ' ' J A N U A R Y ,\ 1899.

T h e obvious duty of one who wishes to decide whether man is “ the modified descendant of some pre-existent form ” or the subject of a special creation is to inquire into the similarities and dissimilarities of his bodily and mental features with those of the lower animals, and to discover how far the variations may be the result of general biological laws. Now, in point of bodily structure, it is notorious that man is constructed on the same general type as other mammals. All his bones, muscles, nerves, blood-vessels, and internal viscera correspond with the like organs in widely different mammals. In brain man is much nearer to the anthropomorphic monkey than the latter is even to the common monkey. Many diseases— hydrophobia, cholera, etc.— are common to man and the lower animals, and are freely inter-communicated. Monkeys are liable to many of our non-contagious diseases ; they are affected by the same remedies, and frequently develop a like taste for alcohol and narcotics. In parasites (internal and external), in the maturation of diseases, the process of the healing of wounds, the phenomena of reproduction and sex, man is strikingly similar to the lower animals. The ovule from which he is developed differs in no respect from the ovules of other animals. The embryo, in its successive stages, corresponds very closely with other animal embryos. Rudimentary organs are found in the human body, which are quite unintelligible unless one supposes them to have been useful to some pre-human ancestor. Rudimentary muscles are found in many parts of the body, notably on the scalp and the ear. The semi-lunar fold of the eye is an atrophied relic of an organ which is still very useful to birds. The sense of smell has much degenerated in man, and the hairy coating of our ancestors is still feebly represented on the human body, especially in the sixth month of development. The appendix vermiformis in the intestines is another remarkable instance, as also are certain features of the humerus. The os coccyx is the evident rudiment of a tail; in the embryo, and occasionally even after birth, it is a true caudal appendage. In man’s rudimentary breasts (which have been known in some cases to produce milk), and in certain features of the generative organ, we find similar traces o f a pre-human ancestry.

THE MANNER OF THE ASCENT.

The actual characteristics o f the human family seem to have arisen by natural selection. There is an infinite variability in human individuals. This is obvious in the face, but it extends also to teeth, arteries, and muscles, The great diversity of mental qualities— there is a corresponding diversity among groups o f the lower animals — is equally notorious. These variations, both corporeal and mental, are transmitted by heredity. The causes of this variability are obscure, but we can see that they are related, as in the case o f the lower animals, to the conditions to which the species is exposed. Having regard to the world-wide extent of the human species, its variability becomes much more intelligible. The influence o f the change of conditions is, however, principally indirect. We have some evidence of the direct action of environment on stature, internal organs, etc. ; but changes more clearly arise as the effects of the increased use or the disuse of organs. Physical labour changes the muscles, the character of food influences the size of the jaws, the rarity of the atmosphere enlarges the chest and lungs, etc. Arrested development, as in the idiot’s brain, is likewise responsible for some variations. A still larger number must be attributed to reversion to an earlier type. The occasional double uterus in woman and certain abnormalities of the malar and the frontal bones are cases in point. There are also instances in man of correlated variation, changes in one organ through some modification o f a different organ with which it is intimately connected.

Now, the early progenitors of man must have tended,

like all other animals, to increase beyond their means of subsistence. A keen struggle for existence would have ensued, and natural selection would act rigorously. Beneficial variations would be preserved and accentuated, injurious characters would be eliminated ; intellectual powers and social habits, man’s most useful endowments, would be particularly fostered. The evolution of the hand, the change from quadruped or quadrumane to biped (with proportionate changes in the osseous structure), the decrease of the jaws and increase of the skull, are easily interpreted in this light. The disappearance of hair is probably due to sexual selection. The shortening of the tail (man has as much tail as the anthropoid apes) is due to his change to an erect attitude.

MIND IN MAN AND THE LOWER ANIMALS. Though so closely related in bodily structure, there is an immense interval between the mind of man and that of the anthropoid apes. Still, there is no fundamental difference between the two sets of mental powers, no intrinsic reason why man’s powers should not be regarded as a development from the psychology of his animal progenitors. There is a still wider interval between the mind of an ape and that of one of the lower fishes, yet it is filled up with numberless gradations. In the first place, man possesses the same senses as other animals, and therefore the same fundamental perceptions. He has also many instincts in common with them— as that o f self-preservation, sexual love, maternal feeling, etc. It does not seem to be true that, as Cuvier claimed, instinct and intelligence are in an inverse ratio : the insects with the most complex instincts are the most intelligent. Many emotions are common to man and the lower animals— pleasure and pain, happiness and misery, terror, suspicion, courage and timidity, anger, love, and revenge. Even the complex emotions of jealousy, humour, pride, etc., are discovered in the lower animals.

On the intellectual plane, animals must certainly be credited with the feeling of wonder, and many of them, especially monkeys, display a large amount of curiosity. The principle of imitation, so strong in savages and in certain morbid states of the brain, is highly developed in many species of animals besides the notorious monkey. The faculty of attention cannot be denied them, and we have many proofs o f their memory and power of imagination (evinced in their dreams). Only a few persons now dispute the animals’ title to the crowning mental faculty— reason. We have many actions of theirs which it is impossible to explain by instinct or the mere association of ideas. It is untrue also that man alone is capable o f progressive development; domesticated animals, for instance, have made considerable progress in moral qualities. T o maintain that no animal during the course of ages has progressed in mental qualities is to beg the question of the evolution of species. Some animals use sticks and stones as tools. There is a degree of self-consciousness in animals, too, and a certain proof of general ideas, or images, and even of mental individuality. Although man alone has the prerogative of articulate speech, involving a highly developed intelligence, still it is notorious that animals freely communicate with each other. The vocal organ of the ape has probably not been developed, owing to its arrested brain development. The crow has fundamentally the same vocal organ as the nightingale. The sense of beauty has been claimed for man alone ; but a study of the amorous relations of animals tells a different story. The possession o f religious belief is, of course, peculiar to man, and is easily explained on the rise of the power of speculation. Yet there is some distant approach to the fundamental religious feeling in the deep love of a dog for his master, associated with complete submission, some fear, and perhaps other feelings.

THE MORAL SENSE.

The moral sense, or conscience, is by far the most