Facing The Future: People and the Planet

 

Farming and Fertility As people turned from hunter gatherers to farmers in the Neolithic period, population began to increase significantly. This was partly due to increased food supplies, as farming techniques allowed production of more food on any given piece of land, and partly because of a decline in mortality as people took up a more settled existence. But it apparently also occurred because fertility increased substantially for the first time in human history. Because of their nomadic lifestyles, hunter gatherer societies tend to have fewer children. A mother in such a society can carry only one child (and what few possessions the family might have) as her community moves about. Other children must be old enough to keep up with the tribe as it moves, so they do not become a burden on the community. This reality dictates that children must be spaced about four years apart - something hunter gatherer societies achieved through sexual abstinence, extended nursing, abortion, or infanticide. Farming societies, by contrast, stay in one place with their crops. Because mobility of children is not a consideration, and because children can contribute to food production from an early age, fertility rates in farming communities are higher, often with birth spacing averaging only two years. All these factors contributed to higher population densities as human lifestyles shifted from hunting-gathering to farming.

The reason for this fundamental change in the way people lived was quite simple - human numbers had grown to the point that it had become necessary. The population had outgrown the capacity of hunting and gathering to support it. (Depending upon the productivity of local ecosystems, it may take as much as one to three square miles of land per person to support a hunter gatherer lifestyle.)

Humans had already penetrated and colonized all the continents by then. They had begun to modify their environments, burning grasslands, clearing forests, and hunting many large species to extinction. Except in areas too cold, too hot, or too dry to support them, they had exploited local ecosystems to the best of their ability. And, apparently, in a variety of regions around the world, they had reached the limits of local resources.

The need to feed larger populations forced people to take up agriculture, because farming produces anywhere from 10 to 100 times as much food per unit of land as hunting and gathering. Human ingenuity and technology made this transition possible, because people had by this time learned how to sow crops and domesticate animals. The need to tend and defend their fields and pastures then required the founding of fixed settlements.

When this fundamental shift from hunting and gathering to farming, and from a nomadic to a settled existence, began, the earth’s population was still quite small, perhaps five to ten million. That number had increased only slowly over the previous two million years, because life was hazardous and short. People probably lived only 20 to 25 years on average, and almost as many people died each year from hunger, accidents, or disease as were born.

Beginning with the Age of Agriculture, however, humans began to prosper, and population began to grow dramatically. (One of the basic realities of biology is that when any organism has excess food and available habitat, its numbers increase.) Farming produced a lot more food than had ever been available in the past, and population grew in response. More people then needed more food, so production was increased, allowing population to grow even further.

From an anthropological perspective, the convergence of agriculture, a settled existence, and population growth is a fascinating time. A number of significant changes occur that we identify with the emergence of civilization.

One of the first changes is architectural. When societies have excess food, they typically build walls to protect it, and people begin to live within those walls.

As food production expands, certain members of society can be freed from producing food to do other things. Some become soldiers to guard that food. Some become administrators, and collect taxes to support those soldiers. Some become priests. (This is the point at which formalized religions emerge, and at which the priesthood becomes a social class.) And some become artisans and inventors, pushing the technological envelope with creations such as pottery, bronze, and the wheel.

As food surpluses mount, it becomes necessary to identify ownership of stored food, and writing systems develop. As social complexity increases, the demand for writing grows. Scribes are needed, as are schools and teachers to train them.

As civilizations expand, they develop legal systems, because once population reaches a critical mass, the type of social enforcement that serves to keep order in tribal groups becomes ineffective. Some sort of justice system - police, courts, prisons and executioners - must be created.

This combination of all these factors led not only to flourishing cultures, but also to unprecedented population growth. By the time of the First Dynasty in Egypt (circa 3000 B.C.E.), global population had grown to an estimated 100 million - 10 to 20 times the increase in human numbers over the preceding 2 million years. By the height of the Roman Empire and the birth of Jesus Christ, that number was perhaps 250 million - almost the size of the United States today.As productivity increased - fostered by inventions such as the plow, pottery, ironwork and the water wheel, as well as a greater understanding of raising plants and animals - food supplies increased further. In response to available food supplies, human numbers increased again. More people then required more land for fields and towns, which in turn led to greater productivity and prosperity, and again to more people.