The first small population of human beings appeared on Earth between 1 and 2 million years ago, probably on the continent of Africa. Since then, the human population has spread out to occupy virtually the entire land surface of the planet and in the last century or two has exploded in numbers to almost 4 billion. Since there are no substantial historical data on which to base estimates of human population size before 1650, estimates must be based on circumstantial evidence. For instance, agriculture was unknown before about 8000 B.C.; prior to that time all human groups made their living by hunting and gathering food. No more than 20 million square miles of the Earth's total land area of some 58 million square miles could successfully have supported our early ancestors. From the population densities of the hunting and gathering tribes of today, we can estimate that the total human population of 8000 B.C. was about 5 million people.

Population sizes at various times, from the onset of the agricultural revolution until census data first were kept in the seventeenth century, have also been estimated. This was done by extrapolation from census figures that exist for agricultural societies, and by examination of archaeological remains. It is thought that the total human population at the time of Christ was around 200 to 300 million people, and that it increased to about 500 million (1/2 billion) by 1650. It then doubled to 1,000 million (1 billion) around 1850, and doubled again to 2 billion by 1930.

Population, Resources, Environment --

 Is Humankind Really In Trouble?

Human values and institutions have set humankind on a catastrophic course with the laws of nature. Human beings cling jealously to their prerogative to reproduce as they please -- and they please to make each new generation larger than the last -- yet endless multiplication on a finite planet is impossible. Most humans aspire to greater material prosperity, but the number of people that can be supported on Earth if everyone is rich is even smaller than if everyone is poor. We are told that only economic growth can ease the pain of poverty -of the inequitable distribution of wealth -- but we know that the quantity of physical goods, like the human population, cannot grow forever. It is not yet clear precisely when and in what form the collision between the growth ethic and natural limits will occur, but there can be no doubt as to the outcome. Human values and institutions will bend or be crushed by biological and physical realities.

Is there any reason to believe, though, that the collision will be sooner rather than later? What is fundamentally different about the 1970s compared with, say, the 1920s or the 1870s? Haven't science and technology always pushed back the natural barriers? Are today's environmental problems the early symptoms of a fundamental disorder or are they merely bothersome side effects of the orderly progress of technology? What would be gained and what would be lost by deferring action until the evidence of impending disaster is more conclusive?

The answers to these questions emerge from the study of several issues:

(1) Human dependence on the natural environment and the fundamental character of our disruption of it;

 (2) Human population and of its impact on the environment;

(3) Why humankind has not yet achieved adulthood;

 (4) The environmental deterioration due to civilization;

 And (5) the stereo-technologic degradation in the modern mind; 

Man and Environment

For our purposes, the environment is the unique skin of soil, water, gaseous atmosphere, mineral nutrients, and organisms that covers this otherwise undistinguished planet. The conditions that make Earth hospitable to human life result from complex and perhaps fragile balances among the great chemical cycles -- water, nitrogen, carbon, oxygen, phosphorous, sulfur -- all powered by the energy of the sun. Deadly ultraviolet radiation from that same life-giving star is kept out by the tiny trace of ozone in the atmosphere; the trace of carbon dioxide maintains the Earth's surface at tolerably warm temperatures by preventing heat from escaping into space. Organisms regulate the environmental concentrations of nitrates, ammonia, and hydrogen sulfide -- all poisonous -- and, in the much longer term, the concentrations of atmospheric nitrogen and oxygen.

In his tenure of some thousands of centuries on this planet, man has learned to modify and to exploit the environment to his advantage in many ways: to clear, to plant, to mine, to dam, to dredge; to domesticate animals, to breed varieties of plants and animals more suitable to his needs, to increase the yields of crops, fish, and fiber he extracts from the natural systems of the planet. Yet, in the last third of the twentieth century, man still cannot claim either full understanding or control of the environmental systems that support his growing population. This is the central truth of the man-environment relation today: man is still part of nature, not master of it. He is exploiting 40 percent of the Earth's land area; he has reduced the mass of land vegetation by one third; ¹ he has power beyond precedent to influence natural environmental systems. But power is not control.

This is the point missed by those who regard environmental concerns as no more than a fad or a rich man's crusade to preserve some scenic places in which to hike or hunt.

Changing Human Behavior: Toward the Environment and Toward Our Fellow Man

 Population control:

 One necessary element in the solution of humankind's problems. Although population control is necessary in this regard, it is far from sufficient. If the population were stabilized immediately around the world, humankind would still be faced by a vast array of problems, many of them potentially lethal. War, racism, misdistribution of income and resources, resource depletion, and environmental deterioration will not be solved by population limitation alone. For example, even 208 million Americans by themselves, continuing along their present course, could in the space of several more decades consume the richest and most accessible of the world's supplies of nonrenewable resources and in the process irreparably damage its life-support systems. Evidently, achieving a prosperous, humane, and environmentally sustainable civilization will require not only population limitation, but also fundamental changes in the social and political institutions that influence other aspects of human behavior.