CLIMATE AND HUMAN HISTORY very different demands on the mineral resources of the soil* It is the quick-growing beast which suffers, because it has to lay by a large quantity of calcium and phosphorus in its skeleton, of iron in its blood, of iodine in its thyroid, all in a short time; while the slower-growing kinds escape—just as in man a degree of shortage of vitamins which is almost without effect on grown men and women may produce serious rickets in growing children. Now cattle are in any case quick-growing animals* A human infant takes six months to double his weight after birth; a calf, in spite of his much greater size, takes only about a month and a half. And in domestic breeds of cattle man hais intensified this quick growth, since his prime aim is the biggest possible return of meat in the short- est possible time. Besides, he breeds for milk-yielding capacities so enlarged as to be almost unnatural. Whereas, for instance, in the natural state cows at one lactation produce two or three hundred gallons of milk, we ask the best modern breeds to give us up to a thousand gallons. The native cattle of Nigeria have their first calf at about six years ; a well-fed cow of a modern breed has hers at three* In beef breeds, the rate of putting on flesh has been doubled. In all these ways, domesticated cattle have been deliberately bred to make more demands upon the soil than other beasts, and the better they are as cattle, the more demands they must make. Accordingly, when good European bulls have been used to grade up native cattle in India or Africa, the result frequently has been merely that the sickness and mortality due to mineral deficiencies have leaped up. Man the stock-breeder has thus been putting new and unprece- dented demands upon the mineral resources of the world's soil. But that is not all. He has also been depicting those resources without making any return. As Sir John Orr says in his book, Minerals in Pastures: "Accompanying the visible movement of milk and beef, there is a slow invisible flow of fertility. Every cargo of beef or milk products, every ship ton of bones, leaves the exporting country so much the poorer." For, in nature, animals die where they live, and the constituents of their bodies are returned to their native soil. But man changes all that. He ships off the bodies of his animals or the products of those bodies to distant countries, and in every exported pound of meat or cheese or bone meal so much phosphorus and »so much calcium and iron and magnesium have been extracted from the soil and removed from the country's shores, Richardson calcul- ates that since 1870 the export of animals from Victoria alone has taken out of its soil the equivalent of two million tons of super- phosphates.