Population Growth Human

The date that the first "human" set foot on earth is more speculation than fact, but it is virtually certain that population growth throughout humankind's early history was painfully slow. Modern humans may have emerged more than 130,000 years ago in the form of Homo sapiens sapiens.

Life for early Homo sapiens was, of course, extraordinarily harsh, with humans wholly dependent on a hunter-gatherer form of existence for the large proportion of history. Dur ing much of that early period, it is doubtful that human numbers amounted to more than a few hundred thousand, given the constraints of the available food supply. Indeed, it may be considered a remarkable achievement that the human race survived at all. Our ancestors did find ways to survive, however, with the discovery of fire making possible a more varied diet and the eventual development of metals. Life was not completely migratory, and it likely featured at least temporary settlements near streams and natural shelter. But in the period from 10,000 to 8,000 B.C.E., the practice of sedentary agriculture is believed to have contributed to what might be termed the first population "explosion." Historical demographers generally place the world's population by the time of the birth of Christ at about 250 million—although it should be pointed out that there is wide variation in such estimates.

The first 1,000 years of the Common Era appear to have been a particularly difficult period for human survival, as numerous famines came and went throughout Asia and Europe. By the year 1000, the global population may have been virtually the same as it had been 1,000 years before. Even after that period, famines, plagues, mortality associated with the rise and fall of dynasties in China, and warfare continued to keep the population growth rate very low—in fact, nearly imperceptible. The Black Death in the fourteenth century may have reduced Europe's population by more than 25 percent and halved that of England. In Latin America, the arrival of Europeans is believed to have almost completely wiped out the indigenous population, from about 40 million in 1500 to less than 10 million a century later.

Most estimates suggest, however, that by about 1600 the decline in world population may have come to an end. But that is not to say that an explosion of population was immi nent. In 1600 the global total may have been about 575 million;150 years later, it had grown to about 770 million, an annual rate of but 0.3 percent. Most of that growth was accounted for by Asia, whose 500 million people made up two-thirds of the world's total, almost the same as today.

The modern period (after 1500) saw modest growth in nearly all regions, with Africa and Latin America as two exceptions. The introduction of previously unknown diseases by European conquerors nearly wiped out much of the indigenous population of the Americas. From a peak of about 42 million in 1500, the population is thought to have dropped to as low as 12 million two centuries later. Although Africa did not experience such devastating losses, population growth was extraordinarily slow after 1600, much of that the result not only of the large numbers of Africans rounded up for the slave trade but also the social disruption that trade caused. Population growth in Africa did not resume until the mid-nineteenth century.

By 1800 the sum total of modern humans was approaching the 1 billion mark for the first time. For the human race's long battle simply to survive, victory was nearly in sight. Various watershed events—such as the development of sewer systems that greatly improved health in cities, the invention of washable cotton clothing, which might have reduced transmission of disease, and growing efficiency in the storage and distribution of food all made significant contributions. Later in the same century, the work of Louis Pasteur advanced the science of medicine in a few short decades—medicine's largest leap forward ever. As a result, the realization that "germs," such as bacilli and viruses, cause disease led to wholesale changes in hospital practices and to the use of immunization against such killers as anthrax, smallpox, and rabies. The impor tance of such discoveries cannot be overemphasized, since the unprecedented expansion of population numbers that was to come in the next century was a result of the "mortality revolution," not a rise in the birth rate.

As can be seen in the Table 1, the twentieth century was truly the "century of population growth," although growth had begun to accelerate in the nineteenth. It should also be remembered that, as the population grew, the absolute numbers of the population additions were necessarily larger. The century opened

Table 1

Number of Years to Add Each Billion to the World Population

Table 1

World

Years to Add

Population

Year

1 Billion

1 Billion

ca. 1800

All of previous human history

2 Billion

1930

130 years

3 Billion

1960

30 years

4 Billion

1974

14 years

5 Billion

1987

13 years

6 Billion

1999

12 years

Source: United Nations Population Division; Population Reference Bureau

Source: United Nations Population Division; Population Reference Bureau with 1.6 billion people on earth and closed with 6.1 billion.

The rapid increase in population growth was caused by the gradual increase in life expectancy that forever changed the span of human life, our expectations, and even economies. Consider mortality in the not-so-distant past: Abraham Lincoln's mother died when she was thirty-five and he was nine. Prior to her death, she had three children: Abraham's brother died in infancy, and his sister in her early twenties. His first love, Anne Rutledge, died at the age of nineteen. Of the four sons born to Abraham and Mary Todd Lincoln, only one survived to maturity.

This is a level of mortality that is unrecognizable today. As the twentieth century progressed, the elimination of many diseases and very sharp reductions in infant mortality changed prospects for the human lifespan to levels that would have been almost incomprehensible in 1890. In the United States, infant mortality in 1915 was such that one in ten infants died within a year of birth, and an approximately equal proportion did not survive to age five. Today, 993 out of 1,000 newborns survive to their first birthday.

As the twentieth century opened, the transformation of a world in which all population growth would shift to the developing countries of Africa, Asia, and Latin America had already begun. It would end with that transformation complete (see Table 2). Today, nearly every developed country is in population decline or on the verge of it (The United Nations definition of more and less developed countries is used here. The UN classifies the countries of Africa, Asia, Latin America, and Oceania as less developed. All other regions are more developed. Exceptions are made for Australia, Japan, and New Zealand, which are classified as more developed despite being in less developed regions.). Only the United States retains a prospect for continued robust population growth, with two-thirds of its growth attributed to fertility and one-third to immigration. But fertility decline was well underway in 1900 throughout Europe and North America. Widespread birth rate decline took place in the developed countries during the Great Depression years of the 1930s and two world wars, along with war mortality itself further reducing the pace of population growth during the century. In the 1980s what may be described as a total collapse in fertility took place in Western Europe, a collapse that quickly spread to the East because of the economic disruptions that followed the breakup of the Soviet Union and its satellites. Fertility is now so low that women in many European countries, at the birth rates of recent years, will average only about 1.1 to 1.3 children during their life-time—unprecedentedly low levels that were not foreseen.

Throughout the twentieth century, the developed countries continued the process that became known as the demographic transition. This general pattern of demographic change theorizes that, as countries develop and become more urban, the high birth and death rates that characterized the preindustrial period will both begin a gradual decline. Fertility will fall as populations shift to towns and cities, where children become less of an economic asset. Rudimentary forms of family

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