Cities are the most artificial habitat man has yet lived in. The environment of a city is radically different from that of the farmer and of the hunter, an occupation man followed for many hundreds of thousands of years -- long enough to become adapted to it. It is only within the past few generations that significant proportions of the human race have lived in the strange environment of cities, to which they have not become adapted satisfactorily, for the death rate and the crime rate are higher in the city than in the country. They do not breed well in the city, either, for the birth rate is lower there.
But city life is fascinating whether one approves of it or not, and with the economic advantages it offers, men and women leave the farms for the city and will continue to do so until a much larger proportion of us live in urban communities.
The city, however, is not one definite type of community life, for there are varieties of cities -- large ones and small, suburbs, factory towns, pleasure resorts, differing greatly one from another. Nor are cities a fixed type of living, for cities, like all else, are changing.
Modern cities are the creation of the railroad, with assistance from the factory. But as the railroad has been supplemented or replaced by the automobile, this new type of transportation, together with the telephone, radio, and moving picture, is modifying the city of the railroad era. Indeed the city as we have known it is being destroyed by these new inventions, and new aggregations of population are being created for which we as yet have no appropriate name but which are sometimes called metropolitan areas. Within these areas are one or more very large cities, several smaller ones of various sizes, some villages, and often a few farms. The inhabitants all read the same newspapers and are linked by a common trading center, and the metropolitan communities are a single area of operations for criminals. Yet there is no single police force for all the places, and no common government.
These same communication inventions are affecting regions as well as cities and making them more alike. Regional differences fade out as isolation disappears. Hence the relation of city to region is changing, for the city dwellers may now come from vast distances. Cities take their personality less and less from the geography of regions. Their differences arise more and more from specialization.
Complexity and heterogeneity lead to specialization, as Herbert Spencer long since showed. It is an age of diversification in occupations. The number and variety are increasing, and each one of us is limiting his work to special fields. Cities do not escape these forces that play upon individuals; they specialize also. Some cities make automobiles, others rubber, or flour, or watches, or moving pictures. Some cities are mainly to sleep in -- huge bedrooms, so to speak; others are for widows and older people who no longer work. Some specialize in climate, others offer aid to health or concentrate on play and recreation, while still others are educational centers.
Nor are these all the changes that the communication and transportation inventions are making. The changes in rural life are so rapid and so radical as to be properly called a revolution. They are due not only to the agencies of communication but to the introduction of power machines, not in factories but on wheels and hence suited to the broad acres of cultivated land. The changes in rural life are not without influence on cities, for cities are made up in large part of peoples who migrate from rural regions, often indirectly through small places, to the cities. This movement, however, may not be so conspicuous in the future.