In compliance with the custom which obliges one to apologize for presenting to the public anything new, it must be explained that this work is an anthropological study of one of the reasons for migration, war, famine and pestilence, and why mankind, in obedience to natural law, is unconsciously organizing to prevent these disasters and to make it possible for every babe to reach old age; - excepting those meeting unavoidable fatal accidents, and even these become avoidable as knowledge increases.
Harmful customs cannot persist or they would destroy the species. War has survived because its advantages were greater than its disadvantages, and it is an instance of the survival of the fittest custom. There is no doubt, nevertheless, that on account of its disadvantages it is being constantly replaced by other methods cheaper in life and money, but which serve the same ends - survival of the most - and in time national wars will cease, but it will be a long time, for such a consummation requires a world-wide organization. In the absence of war there are other factors which prevent survival of all children, and necessitate a large birth rate.
The work, therefore, takes up the reasons for the increase, spread and organization of populations, together with the checks to overpopulation. It merely applies to man the natural laws which are known to govern the spread of all other species of plant or animal. It then explains the relationships of higher and lower races of man, and shows why we expanded across the Atlantic to America in the sixteenth and seventeenth centuries, and thence across the Pacific, and why the higher races must always control the tropics, though acclimatization and colonization are not possible.
To explain the reasons for our expansion to the Philippines and why such a move is but a part of the course of human events, which can be traced back to prehistory, it was necessary to prove the one fact of universal overpopulation. This brought into the discussion many other topics which are apparently disconnected but which are really all bound together, and which must be explained if we are to understand why the retention of the Philippines may be our future necessity. To reduce the text to reasonable limits, much has been omitted which merely emphasized what had already been explained. On a few topics, such as the need of nitrogen nourishment in or out of the tropics, there is a profusion of evidence, which would be unduly extensive were it not for the fact that it is not otherwise possible to dispel popular misconceptions.
Throughout it has been the object to describe merely the facts and the laws governing them. There is no right or wrong in natural phenomena, and therefore no attempt has been made to hide the awful brutality, suffering, poverty and mortality which have been part and parcel of man's evolution to the present point in which modern civilization makes the suffering of a new kind.
Above all else there has not been presented any Utopian plan for curing nature. The facts are stated, and if we are shocked we must remember that it is natural that most of us must be crowded out of existence long before reaching the biblical age of three score and ten. Ethics never bothers nature, and we are governed by natural law to an extent we have never realized.
Most of the manuscript was written in various parts of the world, while actually collecting the data and observing the phenomena described. Particular emphasis, of course, has been given to the conditions in the Philippines - topics of which most Americans are sadly ignorant.
My thanks are due to Dr. George M. Gould and Mr. H. I. Brock for most valuable scientific and literary criticisms, to Dr. Clark I. Wertenbaker for his careful revision of the proofs, and Dr. Victor E. Watkins for revision of manuscript. For the index I am indebted to Messrs. Max Weinberg and Frank H. Rand, to whom thanks are also expressed.