When Malthus first wrote about overpopulation he suggested as a remedy that we should delay the time of marriage. He was unaware of the fact that this delay takes place naturally for other reasons, and that as a rule the higher civilization the greater is the average age at marriage, irrespective of the number of marriages. It results from the greater preparation needed in higher civilizations before men are able to take care of their offspring, and it resembles in effect the postponing of puberty in certain large mammals. The elephant, for instance, is quite aged before it is able to produce and care for its young. In lower tropical civilizations, where the children are nursed until they are almost able to look after themselves, and when they require no clothing, their rearing is nothing more than an animal operation. Kids are raised by the goats just about as well as children of the savage. There is, then, no reason at all, why men should not marry soon after puberty, and this they actually do. Almost every Filipino boy of eighteen, even sixteen, is married, and women are generally grandmothers at thirty. In higher civilizations it takes the youth many years to learn a business or trade; in savage life the boy of fifteen knows as much as he ever will. In civilization it takes years to prepare a home, a little capital, clothing, etc.; in savage life these are not needed. To raise her fewer children the woman also in civilization needs more of education and preparation than in savage life. Hence, those women who matured very early were not fitted for matrimony, and their progeny were handicapped in the struggle for existence and did not survive in as many numbers as the offspring of the women of delayed maturity.

From all these facts it resulted that those civilized men, ages ago, who delayed marriage because their puberty was delayed, had a better chance of survival than those who, through very early puberty, married early and were unable to give their offspring the care bestowed upon the offspring of the better-prepared man. Then the ordinary law of natural selection secured the best type, and it was inevitable that puberty should be gradually delayed by natural law as civilization advanced in the evolution of the Teuton type of man. At present this evolution has made a difference of at least four years in the age of puberty in the North and South of Europe. As a rule these differences have invariably been explained as a result of climate, but this is not wholly correct. Any change of climate disturbs menstruation. All American women who go to the elevated plains of our Northwest, as well as those who go to the tropics, have much temporary' trouble this way, but it is due to changes in vasomotor nerves and the loss of control over the circulation.