Primitive man subsisted exclusively on the foods obtained in his immediate neighborhood, for even if he could have imported them he had nothing with which to buy. The basis of civilization is the farmer's ever increasing ability to raise more food than he needs, thus permitting him to sell to men engaged in other pursuits. Commerce is, therefore, essentially a system of trading something for food, and from the dawn of civilization there has been a rising volume of trade which permitted farmers and stockmen to feed more and more men of crowded communities engaged in the manufacture of non-edibles. This division of labor has had the effect of grouping mankind into masses fed from surrounding territory. At first the means of transportation were so poor that the groups were small, as they could be fed from only a small area, but as roads and vehicles became more efficient the villages grew to towns and cities whose food came from immense distances. Rome, for instance, was once fed from a small area, then from all Italy; but she did not become an immense city until she obtained possession of the wheat fields of Egypt, and when she lost that control her population dropped to what could be fed locally. Modern cities have as high as a thousand people per acre, and some blocks even more, and their food comes from farms thousands of miles away.
The effect of civilization, then, is to cause certain areas to be supersaturated, or contain more people than can be fed from the foods of the place, while other areas are undersaturated or contain fewer people than may be supported by its foods. The two groups of populations are not complementary by any means, because famines exist in one place while foods are wasted in others, but the trend of civilization is to increase transportation facilities so greatly that all the surplus of one place will be utilized in others, and every advance in transportation increases the supersaturation of certain places.
Cold storage and other means of preserving foods need only be mentioned in passing, for without these modern inventions the transportation of foods would be impossible in anywhere near their present amounts. England alone uses 300 refrigerator ships to keep her fed, and our cold-storage exports value a quarter billion dollars. As these two phenomena of super-saturation and undersaturation are the basis of national organization, and are bound to have a profound influence in the future evolution of society, it is amazing that they have received so little attention from sociologists and statesmen as to be practically unrecognized. It is, therefore, of vital importance to study them in considerable detail to understand why the northwestern corner of Europe seems destined to be densely packed with humanity fed from all over the world.
When America was discovered it had more Indians than could be fed, for they were constantly at war for hunting land, but it was far from the saturation point for whites. Hence, the increase of white population has been phenomenal, thirty to thirty-five per cent, per decade, though our rate of increase is diminishing because we are approaching our saturation point. Besides feeding our own twenty-eight persons per square mile we export so much food that probably 125,000,000 (thirty-four per mile) could be supported now. A short while ago, our last vacant lot of land - Oklahoma - was wholly without civilized population. "Its growth has been one of the marvels of Western development. For an agricultural territory, the population is already large, while the farm products have reached almost incredible proportions. The mineral resources, which are almost untouched, are believed to be most bountiful. The future of such a field is not hard to estimate in a country in which great developments are now but a repetition of recent history".
Americans have contracted the habit of congratulating themselves as being in some way the authors of their great prosperity and enormous population, but it is the result of finding an under-saturated land whose great wealth had never been extracted. The 1900 census report contains the curve of the population increase of several European nations and the United States during the previous hundred years, and clearly shows the rapid increase of our undersaturated country, and the slower increases of European countries which have been saturated since man's origin and whose increase had previously depended upon the slow evolution of food production. In England, for instance, in 1480, when dependence was upon home-grown foods, the population was but 3,700,000; in 1580 it was 4,600,000; in 1680 5,500,000; in 1750, 6,500,000; in 1780 it was 9,500,000, though others estimate the population as less than 9,000,000 in 1800, or an increase of only sixty-six per cent, in 150 years - about four per cent, per decade. From 1480, it averaged only two and five-tenths per cent, per decade. In 1800 a tremendous increase began with her ability to buy and import food, and her rate has been thirteen per cent, per decade. Now she imports three-quarters of her wheat,* and most of her other foods, writers varying in their estimates from one-third to three-quarters, so that her 300 people per square mile is very great supersaturation. If her factories fail or other nations seize her markets, so that she cannot buy food, her population must decrease.