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The most discernible trend during the physical stage of development is growth of population. In the physical stage, the primary goal of society was to ensure the survival of the community in the face of war, famine, and epidemic disease. The first result of progress in agriculture, defense and urban settlements was an increase in population. In the modern age of the population explosion, growth of population is often viewed as a barrier to development rather than a measure of it. But in prior centuries, population growth has always been limited by the capacity of society to sustain larger numbers of people. Until very recently, each improvement in agricultural productivity and food supply has resulted in a significant expansion of population. Before the invention of cultivation about 10,000 years ago, the total population of the world probably did not exceed 10 million people. During the next 8000 years, the world’s population increased about 30 times to reach 300 million in 1 AD. Since then it has grown another 20 fold. It reached 500 million in 1650, then doubled to cross one billion by 1800, doubled again to 2 billion by 1930, then tripled during the last six decades. The 12-fold growth of population over the past 300 years as a result of tremendous increases in food production and public health is an indication of the order of magnitude of social progress during this period. Figure 1 utilizes population growth as an index of the growth in social productivity over the last 500 years.

These enormous increases in population were made possible by tremendous advances in the organization of society around urban centers. Historically, the first major organizational innovation was the transition of primitive society from hunting and gathering to cultivation and rearing of domesticated animals between the 7th and 3rd Millennium BC. The capacity to generate reliable supplies of food from the land made possible the establishment of permanent sedentary human settlements. As agricultural productivity increased the supply of food, the surpluses freed more and more people from the necessity of producing and gathering food, so they could specialize in other activities. The size and location of these early settlements was limited by the productivity of the surrounding lands. Later, improved transportation made possible by the development of the wheel, roads, boats and canals enabled food to be carried over greater distances from fields to towns.

The concentration of population in early agricultural settlements led to development of fortified towns, providing physical security from external threats. The creation of towns represents the development of a higher type of physical organization. With few exceptions, these cities were very small by modern standards, rarely exceeding 100,000 inhabitants, but more densely populated than the most crowded modern metropolises. The formation of towns required the evolution of new organizations for governance, external defense, internal security, regulation of property rights, production, trade, distribution, education and religion. Within the town, the workforce divided and specialized into military, political, administrative, agricultural, industrial and commercial categories. The concentration of larger populations increased the frequency, speed and intensity of social interactions, providing far greater need and opportunity for economic exchange than occurred in sparsely populated rural areas. It created pressure on society to continuously increase food production. It created a growing market for goods and services that encouraged social inventiveness.

The growth of these population centers in turn depended upon and was facilitated by advances in the physical organization of the settlement. Towns were organized into sectors. Roads were laid, bridges were built, markets were constructed and ports were developed. In some instances aqueducts were built to transport drinking water and sewers were dug to carry away wastes and drain rainwater. This physical infrastructure enabled towns to grow into larger urban centers, further intensifying the number, size and variety of economic interactions. Cities became centers for government, trade, manufacturing, education, recreation and cultural activities. These densely populated areas where people, capital and knowledge accumulated became powerful engines for development. Packed into close quarters, news and rumors spread swiftly. The population became far more aware of what was taking place in other places. Pioneering inventions and innovations were quickly imitated by others. The growing frequency, efficiency, speed, complexity and intensity of human interactions through the organization of urban communities was the basis for the significant developmental achievements of the physical stage.

The process of urbanization that began with permanent agricultural settlements progressed very slowly up through the Middle Ages. The dual imperatives of defense and sustenance remained the principle rationale for cities and fortress towns under the feudal order. Urban communities in Europe grew more rapidly in size and number with the decline of feudalism and the rise of the mercantile era from the 12th Century onwards. Commercial communities governed by merchant councils flourished throughout Europe and exerted continued pressure for increasing economic freedom and political autonomy from feudal and monarchical power, which led eventually to the emancipation of individuals as well. The growth of merchant cities was made possible by the rapid development of a higher level of commercial organization and the increasing role of money. The growth of the money economy ushered society into the vital stage and spurred the remarkable expansion of global economic activity that led up to the Industrial Revolution.

The final chapter in the growth of urban organizations did not occur until the sustained population explosion of the last three centuries. By the time world population crossed one billion in 1800, only three percent of humanity lived in cities of 20,000 or more. Only 45 cities in the world had populations greater than 100,000. London was still too small to qualify for this elite group of urban centers. By the time world population crossed three billion in 1960, 25 percent of humanity was living in cities. The world’s urban population rose to 40 percent by 1980 and is projected to cross 50 percent by the year 2000. This radical shift of settlement patterns over the last 200 years was spurred by the onset of the Industrial Revolution and has been fueled by the continuous emergence of ever more powerful organizations characteristic of the mental stage of social development.