Others are so imbued with the universality of natural selection as a beneficial law of Nature that they object to our interfering with its action in, as they urge, the elimination of the unfit by disease and death, even when such diseases are caused by the insanitary conditions of our modern cities or the misery and destitution due to our irrational and immoral social system. Such writers entirely ignore the undoubted fact that affection, sympathy, compassion form as essential a part of human nature as do the higher intellectual and moral faculties; that in the very earliest periods of history and among the very lowest of existing savages they are fully manifested, not merely between the members of the same family, but throughout the whole tribe, and also in most cases to every stranger who is not a known or imagined enemy. The earliest book of travels I remember hearing read by my father was that of Mungo Park, one of the first explorers of the Niger. He was once alone and sick there, and some negro women nursed him, fed him, and saved his life; and while lying in their hut he heard them singing about him as the poor white man, of whom they said:— "He has no mother to give him milk, No wife to grind his corn." Hospitality is, in fact, one of the most general of all human virtues, and in some cases is almost a religion. It is an inherent part of what constitutes "human nature," and it is directly antagonistic to the rigid law of natural selection which has universally prevailed throughout the lower animal world. Those who advocate our allowing natural selection to have free play among ourselves on the ground that we are interfering with Nature, are totally ignorant of what they are talking about. It is Nature herself, untaught, unsophisticated _human_ nature, which they are seeking to interfere with. They seek to degrade the higher nature to the level of the lower, to bring down Heaven-born humanity, in its essential characteristics only a little lower than the angels, to the infinitely lower level of the beasts that perish. * * * * * The conclusion reached in the earlier portion of this volume, that the higher intellectual and moral nature of man has been approximately stationary during the whole period of human history, and that the cause of the phenomenon has been the absence of any selective agency adequate to increase it, renders it necessary to give some further explanation as to the probable or possible origin of this higher nature, and also of that admirable human body which also appears to have reached a condition of permanent stability. CHAPTER XV THE LAWS OF HEREDITY AND ENVIRONMENT