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.
 

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Facing The Future: People and the Planet

Impacts of Growth

 

The Rise and Fall of the Fertile Crescent The rise of highly organized and successful civilizations in the Fertile Crescent (in the fourth millennium B.C.E.) was due to a fortunate mixture of natural resources. Numerous plants and animals could be easily domesticated, including wheat, barley, peas, sheep, cows, and pigs. The area also possessed fertile soils and adequate water supplies for irrigation. But because of limits on soil area and depth, the larger populations that resulted from increased food production and prosperity soon overran the resource base. The need to feed ever-larger populations caused farmers to overwork and over-irrigate their fields, resulting in depletion and salinization of the soil. Fertile Crescent societies initially responded by putting more land in production, and by shifting from wheat to barley (which is more tolerant to salt). These measures provided only temporary relief, however, and food shortages eventually undermined the civilizations. Initially the centers of power stayed in the Fertile Crescent, shifting in succession from Babylon, to the Hittites, Assyria and Persia. Power shifted west in the fourth century B.C.E. when Alexander the Great conquered all the advanced states from Greece to India. It shifted further west when Rome conquered Greece in the second century B.C.E. When Rome fell, the center of power moved again, to western and northern Europe. ". . .Fertile Crescent and eastern Mediterranean societies had the misfortune to arise in an ecologically fragile environment," writes Jared Diamond in Guns, Germs and Steel: The Fates of Human Societies. "They committed ecological suicide by destroying their own resource base."

Photo courtesy of Chris Calwell.

Civilizations typically arose and flourished due to the availability of resources such as fertile soils and good water, minerals for metalwork, or forests for fuel and shipbuilding. In the prosperous times that followed the exploitation of those resources, population tended to increase. That larger population then exploited the resource base to a greater degree.

At some point a threshold was reached, beyond which the resource base could no longer support the population. The resulting disruption then caused problems similar to those we see today from severe population pressures - social and economic turmoil, hunger, migration, and war.

As civilizations faced extreme resource scarcity, typically one of three things happened: they overran another civilization to secure new resources (and were often assimilated); or, in their weakened condition, they were overrun by another culture: or, they simply collapsed and their people dispersed. We can see this in our cultural birthplace in the Fertile Crescent, and the progression of civilizations that flourished and collapsed there - from Babylon, to the Hittites, to Assyria and to Persia. All of these societies committed what author Jared Diamond calls "ecological suicide."

The transition from nomadic lifestyles to agriculture and civilization as we know it began in three primary regions of the world - Southwest Asia, China, and Mesoamerica. But none of those areas could sustain the intensive agriculture necessary to support large populations, and all became increasingly degraded. Because of food scarcity, large numbers of people lived on the edge of starvation.

Resource scarcity also caused other impacts. As historian Gwynne Dyer wrote, "The basis of civilization is agriculture, which transforms the land into a valuable possession that requires protection." It is understandable then, that the first recorded war in human history was fought between two cities in the Tigris-Euphrates Valley over the movement of a boundary stone marking fields. To threaten a society’s farmland was to threaten its food supply, which was to threaten its very existence.

Since that time, countless wars have been fought over hunting grounds, farmland, forests, water, salt, minerals, or control of strategic areas or trade routes. Underlying all of these conflicts were the greater needs of greater numbers of people.

Viewed through a demographic lens, the rise and fall of civilizations fits a similar pattern. The Hyksos conquest of Egypt around 1600 B.C.E., for example, is credited to their use of horses and chariots. But driving that conquest were population growth and resource scarcity, compounded by deforestation, desertification, and soil erosion in the Hyksos’ original homelands in Syria and Palestine. When their traditional home could no longer support their population, the Hyksos seized the richest territory they knew of, which was Lower Egypt.

The expansion of the Greek Empire can be similarly linked to population pressures. By 650 B.C.E., population had increased significantly in response to the prosperity brought by trading. Unfortunately, environmental destruction - primarily manifested as deforestation and soil erosion - also increased. Plato, in his Crititas, observed that, "What now remains compared with what then existed is like the skeleton of a sick man, all the fat and soft earth having wasted away, and only the bare framework of the land being left. . ."

The combination of population growth and environmental destruction meant that the supply of farmland - and therefore food - was insufficient to meet the needs of Greece. This stimulated Greek colonization of the forest and farmlands around the Mediterranean and the Black Sea.

The rise of Rome was also profoundly affected by increasing human numbers. The fledgling civilization fought its first major wars against the Samnites of northern Italy, who were forced by population growth down into the Roman province of Campania in search of farmland. After three major wars, the Romans prevailed.

They then employed their expanded and improved army to seize additional cropland, forest areas, and mineral resources all around the Mediterranean. With a larger population, a larger army, and a booming economy due to captured resources, Rome became the world’s first great empire.

But population growth and the resulting environmental destruction also contributed to the fall of Rome. The constant need to feed more people, maintain standing armies and support a growing economy forced the Romans to overexploit their resource base.

Rome had guaranteed every citizen a daily ration of bread since 58 B.C.E. to assure political stability. To create fields to produce enough grain (and to provide construction and shipbuilding materials), forests were cleared around much of the Mediterranean. Deforestation and erosion worsened as fields were carved out on ever steeper slopes in an attempt to produce still more grain. Rome was forced to virtually abandon several major cities such as Leptis Magna, in what is now Libya, as erosion and climate change caused by deforestation destroyed their harbors and grain fields.

The Empire began gradually to contract as environmental destruction, outside military pressures, and internal dissent mounted. By the time the Roman capitol was overrun in the early fifth century C.E. by the Goths, the western Empire was only a shadow of its former glory.
 
 

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Facing The Future: People and the Planet

Setbacks

Historically, human numbers were greatly limited by disease. This was especially true as growing populations became more concentrated in cities, where people were more easily exposed to infectious agents. (It takes a minimum population for diseases to sustain themselves. Measles, for example, requires about 7,000 susceptible individuals to assure its survival. A regional population of from 300,000 to 400,000, with regular contact, is probably the minimum necessary to sustain that disease.)

Photo by Alwyn Jones

Plague devastated Athens in 429 B.C.E., and large parts of China 200 years later. It ravaged the Roman Empire from 160 to 184 C.E., killed a large percentage of the population of Constantinople in 542 C.E., and reached Britain by 547. By the end of that cycle in 594, the population of Europe had been halved. Plague returned periodically, peaking in the fourteenth century, when it killed an estimated one third of the population of Europe.

Other diseases were equally devastating, if more localized. When Spanish conquistadors invaded Mexico in 1517, the native population was perhaps 25 million. In less than a century, it had fallen to just over one million due to introduced diseases, such as measles. In South America, the introduction of smallpox by Europeans damaged the Inca Empire so badly that Pizarro’s few soldiers, horses, and guns easily toppled it.

Famine also slowed population growth, appearing regularly around the world from the earliest times of recorded history. The Near Eastern and Mediterranean worlds were always susceptible to famine, as indicated by Biblical references.

Famine was an integral part of Roman history, and closely linked to the final collapse of the Empire. As its population grew, and environmental destruction limited local productivity, the Empire became dependent on foreign sources of grain. As the Empire contracted - and grain–producing lands in Germany, Egypt, and Britain were lost - Roman authorities were unable to provide the guaranteed distribution of food that had long maintained domestic stability. Between 400 and 800 C.E., the population of the city of Rome fell by over 90 percent, largely because of famine.Large-scale famine also occurred in the Byzantine Empire in 927, in Japan in 1232, Germany and Italy in 1258, England in 1294 and 1555, all of Western Europe in 1315, Russia in 1603, Bengal in 1669 and 1769, Ireland in 1845-49, and China and India in 1876 and 1879. Tens of millions died in these events, sometimes reducing local populations by as much as one third or more.Despite these setbacks, however, population continued to grow overall. By 1500, world population had reached an estimated 500 million. It was around this time that the era of western colonial expansion began in earnest, driven by the demands of more people for more resources.

The Great Wall of China and the Sack of Rome

Population pressures have always shaped human history. The connections are not always obvious, however, because they may be quite slow-acting. Consider how construction of the Great Wall of China ultimately led to the sack of Rome.

In the third century B.C.E., a civilization of nomadic warriors flourished in Mongolia. The Chinese called these people Hsiang-Nu, but in the west, they became known as the Huns. As their population increased, the Huns gradually moved south, and began to raid China.

The Chinese responded by building the Great Wall. The Huns continued to raid around the Wall, and the Chinese ultimately had to extend their defenses. They captured and fortified the Tarim Basin all the way to foothills of the Pamir Mountains. Unable to penetrate this barrier, the Huns were forced west into Central Asia.

A few centuries later, another group of nomadic warriors arose in Mongolia. The Chinese called these people the Juan-Juan, but modern historians call them the Avars. The Avars also raided south, were unable to penetrate the Great Wall, and were forced west.

In Central Asia, the Avars collided with the Huns. The Avars, with a major technological advantage (the stirrup, which makes fighting from horseback much more efficient), defeated the Huns and drove them further west. At the Dniester River, the Huns collided with the Goths, who were being held out of the Roman Empire by a combination of treaties, bribes, and Roman Legions. When the Huns fell on the Goths, they slaughtered them in great numbers, and drove the survivors across the river into Roman territory.

Once the Goths had penetrated the Empire, they found it an empty shell. They smashed through southern Europe, crushed the remaining Roman Legions, and sacked the capital in 410 C.E.

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Facing The Future: People and the Planet

The Age of European Expansion

 

The Potato and the American Civil War When Spain and Portugal began their colonial expansion, northern Europe was largely a backwater. Shorter growing seasons limited grain production, so the area lacked the caloric resources to undertake significant exploration and conquest. But when Spanish explorers brought the potato back from South America, everything changed. Potatoes grew well in cooler climates, and provided lots of calories. With more food available, population increased rapidly in England, Holland, Germany, Poland and Sweden. When those countries faced shortages of farmland, jobs, and other resources due to population growth, they experienced massive out-migration, primarily to the northern US. Because of this influx, US population grew roughly 35% every decade from 1800 to 1860. This caused a huge demographic shift. In 1800, the South was home to half the US population. but by 1860, it represented just over one-third. In 1847 the Union comprised 15 slave and 14 free states, so southerners maintained control of the US Senate. But as immigration fueled western expansion, new states began to arise. The South tried desperately to ward this off. It stonewalled the Homestead Act and the transcontinental railroad, because those would promote western settlement. And it attempted to create new states where southern institutions could flourish. In the 1840's and 50's, southerners led or sponsored three attempted invasions of Cuba, three efforts to seize Nicaragua, and one invasion of Baja California. They also tried to purchase the northern third of Mexico. None of these efforts were successful, nor could they offset the relentless forces of population growth. By 1860, slave states were a minority, and political power had shifted north. By 1861, southerners knew they had only two choices. Either surrender slavery, or fight (and win) a war of secession.

The first Europeans to actively colonize other regions were the Vikings. The forces behind their expansion were complex, but scarcity of farmland was a key element. As historian J.M. Roberts wrote, "These Scandinavians combined trade, piracy and colonization, stimulated by land hunger."

The first known Viking raid occurred in 793 C.E., and over the next 400 years they discov–ered and settled the Faroe Islands, Iceland, Greenland, and parts of Newfoundland.

Moving east and south, the Vikings penetrated the heartland of Russia (which is named for the Rus, as the Vikings were called there) and founded city-states such as Kiev and Novgorod. They raided as far south as Constantinople and Baghdad, and threatened French cities to the point that they were given huge tracts of land in what is now Normandy ("land of the Northmen") in exchange for peace. And they conquered much of the richest farmland of Northern England and Ireland.

By the early 15th century, Portugal had begun to explore and exploit the West Coast of Africa. The wealth they captured created an economic and population boom at home, and stimulated further explorations. The Portuguese pushed down the coast of Africa, then eastward. They established trading colonies in India about the time Columbus reached the Caribbean, and launched the era of Spanish exploration and colonization.

While the early European empires were seen primarily as sources of wealth, the flood of resources they returned to Europe caused a profound shift. As expected, increased prosperity stimulated local population growth in Portugal and Spain. But new protein sources increased the ability of northern European nations to produce food, and their populations began to expand rapidly.

Less than 100 years after the introduction by the Spanish of the potato from South America and maize corn from Mexico, England and Holland had joined the scramble for overseas colonies.

This new burst of growth (world population grew as much between 1500 and 1750 as it had in the previous 1500 years) created renewed scarcities, particularly of farmland. Because of this, smaller nations such as England and Hol–land began to see colonies not only as a place to obtain resources from, but also a place to send excess population to.

This trend continued through the 19th century, with nations such as Germany, Sweden, and Norway, as well as British-occupied Ireland, also reducing population pressure through emigration to North America.

Conflict between nations intensified throughout the Age of Expansion, as competing powers fought over trade routes and access to resources in North and South America, Asia and Africa. But conflict also occurred on a more local scale, as the new arrivals clashed with indigenous populations.

As European settlers expanded across North America, for example, they displaced or dispossessed Native inhabitants. Those peoples were then forced to migrate, and subsequently displaced the tribes onto whose lands they were driven. If they failed to do so, they vanished as a culture.

As Americans pushed further west in search of more land and resources to supply a growing population, more clashes followed.

By the time the western edge of the continent was reached, the new immigrants controlled the majority of land and resources, and most surviving indigenous populations were relegated to reservations.

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Facing The Future: People and the Planet

World population growth continued through the nineteenth century at a high rate, spurred by a general economic expansion, and increased food production as new lands were opened up. Around 1830, human numbers reached one billion for the first time.

The Industrial Revolution generated a tremendous economic boom, as machine power made mass manufacturing possible. Steam-powered transportation systems allowed people and goods to move easily from one place to another, while mechanization made it possible for fewer farmers to work more land. And the possibility of working for cash wages opened up opportunities to accumulate capital and to move it easily, whether for investment or migration.

Improved living conditions and an optimistic view of the future also contributed to increased birth rates in many areas. People in the past had sometimes limited family size due to re–source constraints (often through abortion or infanticide), but they now began to have more children.

Just as birthrates in the US dropped during the Great Depression and rose after World War II (the "baby boom"), they peaked in Europe during times of peace and prosperity in the nineteenth century. French birth rates peaked after the Peace of Amiens in 1802. Russian birth rates peaked after the freeing of the Serfs in 1861. And German birth rates peaked after the formation of the Empire in 1871.Despite a subsequent drop in birth rates in the late nineteenth and early twentieth centuries - as more people moved to cities and larger families were no longer needed to work the land - population growth continued. Advances in medicine and sanitation lowered mortality and increased life expectancy. During the Civil War, health care workers demonstrated that steps as simple as doctors washing their hands between operations and sterilizing instruments dramatically reduced infection. Development of safe water sources, sewer systems, and food preservation technologies also improved health.

Photo courtesy of Chris Calwell.

The work of Koch, Lister and Pasteur provided increased understanding of infectious agents, while the development of general anesthetics, X–rays, and corrective surgery saved countless lives. The invention of antibiotics, such as sul–fonamides and penicillin in the 1930’s, allowed treatment of many previously fatal infections, and vaccinations protected people against diseases such as smallpox, typhoid, and measles.

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Photo courtesy of Alwyn Jones.

It took all of human history for population to reach one billion, but barely a century to reach two billion. The third billion was added in just 30 years and the fourth in only 15 years. Today, we’re adding another billion people roughly every 12 to 13 years. If current rates of increase continue, world population will double again in just over 40 years.

The vast majority of this growth will occur in the developing world. Africa is growing at a rate that, if maintained, will lead to a doubling of population in under 25 years. While most de–mographers expect fertility rates to decline, South Central Asia is currently on track to double its population in 30 years, and Central America to double in 35 years.

The choices we make in the next few years will determine our demographic future. It is possible to stabilize population through just, humane, culturally-appropriate methods. We can do this by investing in reproductive health care, education, empowering women, poverty alleviation, human rights, and sustainable development. Or we can watch population spiral out of control until natural laws intervene - as they have throughout history.

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