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For most of our history, humans lived by hunting and gathering, and our population was probably not more than a few million. The invention of agriculture and the domestication of animals around 10,000 years ago allowed our numbers to grow. With a larger and more secure food supply, the population reached perhaps 50 million people by 5000 B.C.E. Still, for thousands of years, the number of humans increased slowly. Archaeological evidence and historical descriptions suggest that only about 300 million people were living at the time of Christ (table 7.1). It took all of human history to reach 1 billion people in 1804, but little more than 150 years to reach 3 billion in 1960. To go from 5 to 6 billion took only 12 years. i Demographers often describe this kind of growth in terms of doubling times (see table 7.1). Over time, the growth rate has accelerated, and the time needed to double the population size has decreased from several hundred years to just a few decades. Population growth was most rapid in the early 1960s, when the global population doubling time fell to 33 years or less. The doubling time is now lengthening again, as birth rates slow around the world. Demographers expect that by 2050 the global population will reach about 9.7 billion, with a doubling time of 155 years or more. However, most analysts hope that the population will not actually double again. While we use doubling time as a relative measure of growth rates, the population is expected to stabilize by about 2100 at around 11 billion.
st Until the Middle Ages, human populations were held in check by diseases and poor nutrition, which caused high child mortality and short life expectancy for those who reached adulthood. There is evidence that many early societies regulated their population size through cultural taboos and practices such as abstinence and infanticide. War and famine also caused episodes of population decline. Among the most destructive of natural population controls were bubonic plagues (or Black Death) that periodically swept across Europe between 1348 and 1650 (fig. 7.3). It has been estimated that during the worst plague years (1348—1350) at least one-third of the European population perished. Notice, however, that this didn't retard population growth for very long. In 1650, at the end of the last great plague, there were about 600 million people in the world.
As you can see in figure 7.3, human populations began to increase rapidly after 1600 C.E. Many factors contributed to this rapid growth.
Increased sailing and navigating skills stimulated commerce and w communication between nations. Trade increased access to resources, including more food. Agricultural developments, better sources of power, and better health care and hygiene also played a role.
We have had an exponential or J curve pattern of growth for centuries. Recently, however, the growth rate has begun flattening, and turning into an S-shaped curve (see section 7.3). If we do not shift to an S-shaped curve, will we overshoot the carrying capacity of our environment and experience a catastrophic dieback similar to those described in chapter 6? Or we will reach equilibrium soon enough and at a size that can be sustained over the long term? No one knows, of course, but in the sections that follow we analyze factors that influence growth rates.

Agricultural revolution

including more food. Agricultural developments, better sources of power, and better health care and hygiene also played a role.
We have had an exponential or J curve pattern of growth for centuries. Recently, however, the growth rate has begun flattening, and turning into an S-shaped curve (see section 7.3). If we do not shift to an S-shaped curve, will we overshoot the carrying capacity of our environment and experience a catastrophic dieback similar to those described in chapter 6? Or we will reach equilibrium soon enough and at a size that can be sustained over the long term? No one knows, of course, but in the sections that follow we analyze factors that influence growth rates.
Every second, on average, four children are born somewhere on the earth. In that same second, one person dies. This difference between births and deaths means a net gain of roughly three more humans per second in the world's population. In 2016, the total world population was at least 7.4 billion people and was growing at 1.08 percent per year. This means we are now adding nearly 80 million more people per year, and if this rate persists, our global population will double in about 66 years. Already humans are among the most numerous and widely distributed of vertebrate species on the earth. We also have a greater global environmental impact than any other species. For families, the birth of a child is a joyous event (fig. 7.2). But collectively, what is the effect of our growing population? The answers to this question depend on our estimates of the causes of change, rates of change, and ideas about resource consumption per person.
Many people worry that overpopulation is causing resource depletion and environmental degradation that threaten the ecological life-support systems on which we all depend. Recall from chapter 6 that carrying capacity is the maximum population size that can be supported for a particular species in a specific environment without depleting resources. Are there enough resources for 8 or 10 billion people to live a good and healthy life? Are we on track to overshoot the Earth's carrying capacity?
Alternatively, can human ingenuity, technology, and enterprise can extend the world carrying capacity and allow us to overcome environmental limits? A larger population means a larger workforce, more inventions, more ideas about better solutions. Along with every new mouth comes a pair of hands. Can continued economic and technological growth provide the stability to reduce population growth voluntarily?
Another question is whether we can address social justice concerns. Countries with the highest current growth rates are also some of the poorest in the world. But the richest countries use the most resources. Many argue that there are sufficient resources for everyone, and the root cause of environmental degradation is inequitable distribution of wealth and power, rather than population size. Fostering democracy, empowering women and minorities, and improving the standard of living of the world's poorest people are what are really needed, from this point of view. A narrow focus on population growth can foster racism and blame the poor for their own poverty, while ignoring the deeper social and economic forces at work.
Will human populations continue to grow at present rates? What would that growth imply for environmental quality and for human life? These are among the most central and pressing questions in environmental science. In this chapter, we examine causes of population growth, as well as the ways populations are measured and described. We also examine factors that slow growth rates and stabilize populations, such as family planning, and the many considerations that influence decisions about family size.
For most of our history, humans lived by hunting and gathering, and our population was probably not more than a few million. The invention of agriculture and the domestication of animals around 10,000 years ago allowed our numbers to grow. With a larger and more secure food supply, the population reached perhaps 50 million people by 5000 B.C.E. Still, for thousands of years, the number of humans increased slowly. Archaeological evidence and historical descriptions suggest that only about 300 million people were living at the time of Christ (table 7.1). It took all of human history to reach 1 billion people in 1804, but little more than 150 years to reach 3 billion in 1960. To go from 5 to 6 billion took only 12 years.
Demographers often describe this kind of growth in terms of doubling times (see table 7.1). Over time, the growth rate has accelerated, and the time needed to double the population size has decreased from several hundred years to just a few decades. Population growth was most rapid in the early 1960s, when the global population doubling time fell to 33 years or less. The doubling time is now lengthening again, as birth rates slow around the world. Demographers expect that by 2050 the global population vill reach about 9.7 billion, with a doubling time of 155 years or nore. However, most analysts hope that the population will not ctually double again. While we use doubling time as a relative leasure of growth rates, the population is expected to stabilize by )out 2100 at around 11 billion.
Until the Middle Ages, human populations were held in check diseases and poor nutrition, which caused high child mortaland short life expectancy for those who reached adulthood.There is evidence that many early societies regulated their population size through cultural taboos and practices such as abstinence and infanticide. War and famine also caused episodes of population decline. Among the most desü•uctive of natural population controls were bubonic plagues (or Black Death) that periodically swept across Europe between 1348 and 1650 (fig. 7.3). It has been estimated that during the worst plague years (1348—1350) at least one-third of the European population perished. Notice, however, that this didn't retard population growth for very long. In 1650, at the end of the last great plague, there were about 600 million people in the world.
As you can see in figure 7.3, human populations began to increase rapidly after 1600 C.E. Many factors contributed to this rapid growth. Increased sailing and navigating skills stimulated commerce and communication between nations. Trade increased access to resources, including more food. Agricultural developments, better sources of power, and better health care and hygiene also played a role.
We have had an exponential or J curve pattern of growth for centuries. Recently, however, the growth rate has begun flattening, and turning into an S-shaped curve (see section 7.3). If we do not shift to an S-shaped curve, will we overshoot the carrying capacity of our environment and experience a catastrophic dieback similar to those described in chapter 6? Or we will reach equilibrium soon enough and at a size that can be sustained over the long term? No one knows, of course, but in the sections that follow we analyze factors that influence growth rates.

Since the time of the Industrial Revolution, when the population growth began accelerating rapidly, scholars have argued about the causes and consequences of population growth. One of the most influential explanations today was proposed in 1798 by Thomas Malthus (1766—1834), in An Essay on the Principle of Population. Malthus argued that populations tend to increase at exponential rates, with an accelerating increase over time. Food production, he proposed, either remains stable or increases only slowly. Eventually, human populations should therefore outstrip their food supply and collapse into starvation, crime, and misery. Population growth, Malthus said, slows only when disease or famine reduces population size, or when constraining social conditions—late marriage, insufficient resources, celibacy, and "moral restraint"—-compel a population to reduce birth rates.
In Malthusian terms, then, population growth causes resource depletion and poverty (fig. 7.4a). At that time, most economists believed that high fertility was good for the economy, increasing gross domestic output. Malthus converted them to believing
that population growth was an economic danger, because per capita output actually fell with rapidly increasing population, and because large populations deplete resources rapidly.
Several decades later, the economist Karl Marx (1818—1883) presented an opposing view. Marx argued that exploitation of workers—such as low wages and job insecurity—causes poverty, which in turn contributes to population growth and other social ills. Poverty can lead to high birth rates, for example, when people in insecure or desperate conditions lack either opportunities (employment or education) or social restraints that discourage early and frequent childbearing. In these conditions, large families can exacerbate insecurity. Others since Marx have argued that the wealthy consume more resources, and cause more resource depletion, than the poor do. Both population growth and exploitation, then, cause resource depletion (fig. 7.4b). Reversing poverty, population growth, and environmental degradation, according to this perspective, requires the elimination of exploitation and oppression of the poor. As Mohandas Gandhi stated, "There is enough for everyone's need, but not enough for anyone's greed."
Mn xand Malthus developed their theories about human eir theories about human popuon growth when views about the world, technology, and society e much different than they are today. But these different views tinue inform competing approaches to family planning and ulation growth. If high birth rates are the driving force, causing rty and extreme resource consumption, then increasing access rth control, or even coercive reduction in family size, is the important strategy to reduce both growth and poverty. If poverty contributes to population growth, on the other hand, then the most important task is to reduce poverty and improve opportunity. This is the path that has been followed in Brazil and many other countries. In most European countries, population growth has fallen to below replacement levels, as education and employment opportunities have improved and people have chosen to have smaller families (see section 7.4).
Both perspectives may be partly right. And while there are multiple interpretations of the best strategy for reducing populations, the question still remains whether, or how soon, we will exceed the earth's carrying capacity. The mathematical biologist Joel Cohen, of Rockefeller University, reviewed published estimates of the maximum human population size the planet can sustain. The estimates he found, spanning 300 years of thinking, converged on a median value of 10—12 billion. We are more than 7 billion strong today, and growing, an alarming prospect for some (fig. 7.5). Cornell University entomologist David Pimentel, for example, has said: "By 2100, if current trends continue, twelve billion miserable humans will suffer a difficult life on Earth."

FIGURE 7.4 (a) Thomas Malthus argued that excess population growth is the ultimate cause of many other social and environmental problems. (b) Karl Marx argued that oppression and exploitation are the real causes of poverty and environmental degradation. Population growth in this view is a symptom or result of other problems, not the source.

If poverty contributes to population growth, on the other hand, then the most important task is to reduce poverty and improve opportunity. This is the path that has been followed in Brazil and many other countries. In most European countries, population growth has fallen to below replacement levels, as education and employment opportunities have improved and people have chosen to have smaller families (see section 7.4).
Both perspectives may be partly right. And while there are multiple interpretations of the best strategy for reducing populations, the question still remains whether, or how soon, we will exceed the earth's carrying capacity. The mathematical biologist Joel Cohen, of Rockefeller University, reviewed published estimates of the maximum human population size the planet can sustain. The estimates he found, spanning 300 years of thinking, converged on a median value of 10—12 billion. We are more than 7 billion strong today, and growing, an alarming prospect for some (fig. 7.5). Cornell University entomologist David Pimentel, for example, has said: "By 2100, if current trends continue, twelve billion miserable humans will suffer a difficult life on Earth."

exacerbate insecurity. Others since Marx have argued that the ealthy consume more resources, and cause more resource deple- ti n, than the poor do. Both population growth and exploitation, en, cause resource depletion (fig. 7.4b). Reversing poverty, pop-

ation growth, and environmental degradation, according to this rspective, requires the elimination of exploitation and oppresn of the poor. As Mohandas Gandhi stated, "There is enough everyone's need, but not enough for anyone's greed."
that population growth was an economic danger, because per capita output actually fell with rapidly increasing population, and because large populations deplete resources rapidly.
Several decades later, the economist Karl Marx (1818—1883) presented an opposing view. Marx argued that exploitation of workers—such as low wages and job insecurity—causes poverty, which in turn contributes to population growth and other social ills. Poverty can lead to high birth rates, for example, when people in insecure or desperate conditions lack either opportunities (employment or education) or social restraints that discourage early and frequent childbearing. In these conditions, large families can exacerbate insecurity. Others since Marx have argued that the wealthy consume more resources, and cause more resource depletion, than the poor do. Both population growth and exploitation, then, cause resource depletion (fig. 7.4b). Reversing poverty, population growth, and environmental degradation, according to this perspective, requires the elimination of exploitation and oppression of the poor. As Mohandas Gandhi stated, "There is enough for everyone's need, but not enough for anyone's greed."
Mn xand Malthus developed their theories about human popu-

exacerbate insecurity. Others since Marx have argued that the ealthy consume more resources, and cause more resource deple- ti n, than the poor do. Both population growth and exploitation, en, cause resource depletion (fig. 7.4b). Reversing poverty, pop-

ation growth, and environmental degradation, according to this rspective, requires the elimination of exploitation and oppresn of the poor. As Mohandas Gandhi stated, "There is enough everyone's need, but not enough for anyone's greed."
will
we:
allow us to overcome limits, argue that resources do not neces-
301
sarily constrain human populations as tightly as other species. As resources become scarce, we tend to invent alternative resources
str



or strategies. They note that Malthus was wrong 200 years ago in
al
his predictions of famine and disaster because he failed to account for scientific and technical progress.
For example, even though urban populations have grown dramatically since Malthus' time, we have invented systems of trade, transportation, sanitation, and building that make cities healthier and safer than in the 1790s. And despite having nearly ten times the global population of Malthus' time, we now have have more and better food resources per capita than ever before. According to the UN Food and Agriculture Organization (FAO), the aver-
al
from an average of 2,100 calories per day in 1970 to 2,700. In 2015. In that same period, the world population went from 3.7 to more than 7 billion people. It's important to recognize that food security is not evenly distributed. In 2015, the UN FAO estimated that there were at least 795 million undernourished people despite the abundance of food produced. However, hunger and famines are generally attributable to politics and economics, rather than underproduction as described by Malthus (see section 9.1).
The burst of world population growth that began 200 years agc was stimulated by scientific and industrial revolutions. Progres in agricultural productivity, engineering, information technology, commerce, medicine, sanitation, and other achievements of modern life have made it possible to support thousands of times as many people per unit area as was possible 10,000 years ago. Economist Stephen Moore of the Cato Institute in Washington, D.C., regards this achievement as "a real tribute to human ingenuity and our ability to innovate." There is no reason, he argues, to think that our ability to find technological solutions to our problems will diminish in the future.
Technology can increase our environmental impacts as well as improving our survival rate. Our environmental impacts result from a combination of population size and how much we consume per person. A summary for this explanation of impacts is I = PAT: Environmental impacts (I) equal the product of our population size (P) times affluence (A) and the technology (T) used to produce the goods and services we consume (fig. 7.6). While increased standards of living in Brazil, for example, have helped stabilize population, they also bring about higher technological impacts. A family living an affluent lifestyle that depends on high levels of energy and material consumption, and that produces excessive amounts of pollution, could cause greater environmental damage than a whole village of hunters and gatherers or subsistence farmers.
If the billions of people in Asia, Africa, and Latin America use conventional, resource-intensive technology to reach the standard of living now enjoyed by rich people in North America or Europe, the environmental effects will be disastrous. Already, growing wealth in China, whose middle class is now estimated at about 300 million, or nearly the entire population of the United States, is straining global resources and has made China the world's largest emitter of C02. There are now more millionaires in China than in all of Europe, and China has passed the United States in annual automobile production.
But China has also become a global leader in renewable energy, public transportation, and electric vehicles. Ideally, all of us will soon be using nonpolluting, renewable energy and material sources. If we can extend the benefits of environmentally friendly technology to the poorer people of the world, then everyone can enjoy the benefits of a better standard of living without the environmental costs historically associated with development and growth
esources, but they also represent gigantic economic engines and sources of innovation. More people mean larger markets, more workers, and efficiencies of scale in mass production
lik



of goods. If future economies are based largely on services, such
ap
as education, information, or data management, then larger popu-
th
lations mean larger markets for those services. Moreover, adding people boosts human ingenuity and intelligence that will create new
re
resources by finding new materials and discovering new ways of
is
Economist Julian Simon (1932—1998), a champion of this rosy view of human history, believed that people are the "ultimate resource" and that no evidence suggests that pollution, crime, unemployment, crowding, the loss of species, or any other resource limitations will worsen with population growth. In a famous bet in 1980, Simon challenged Paul Ehrlich, author of The Population Bomb, to pick five commodities that would become more expensive by the end of the decade. The resources Ehrlich chose, copper, chromium, nickel, tin and tungsten, actually declined in price, by an average of 50 percent. Simon, the technological optimist, won the bet. It has been argued that the 10 year span was too short, or that different resources might have performed differently, but it remains true that resource substitution has made many formerly critical resources cheap or obsolete. Leaders of developing countries insist that, instead of being obsessed with population growth, we should focus on the reducing consumption of the world's resources by people in richer countries (see fig. 7.18).
There were at least 7.4 billion people in the world in 2016, but that is only an educated guess. Even in this age of information technology and communication, counting the number of people in the world is like shooting at a moving target. People continue to be born and die every moment. Some countries have never even taken a census, or the censuses that have been done may not be accurate. Governments may overstate or understate their populations to make their countries appear larger and more important or smaller and more stable than they really are. Some individuals, especially if they are homeless, refugees, or illegal aliens, may not want to be counted or identified.
We really live in two very different demographic worlds. One is old, rich, and relatively stable. The other is young, poor, and growing rapidly. Most people in Asia, Africa, and Latin
America inhabit the latter demographic world (fig. 7.7). These countries represent 80 percent of the world population but more than 90 percent of all projected growth (fig. 7.8). The highest population growth rates occur in a few "hot spots," such as sub-Saharan Africa and the Middle East, where economics, politics, religion, and civil unrest keep birth rates high and contraceptive use low. In Niger, for example, annual population growth is currently 3.9 percent. Less than 10 percent of all couples use any form of birth control, women average 7.6 children each, and nearly half the population is less than 15 years old. Even faster growth is occurring in Qatar, where the population doubling time is only 7.3 years. Obviously, a small country with limited resources (except oil) and almost no fresh water can't sustain that high growth rate indefinitely.
Some countries in the developing world have experienced extremely rapid growth rates and are expected to increase dramati3a11y by the middle of the twenty-first century. Table 7.2 shows the en largest countries in the world, arranged by their estimated size
2013 and projected size in 2050. Note that, although China was e most populous country throughout the twentieth century, India expected to pass China in about 2022. Nigeria, 33 million residents in 1950, is forecast to have around 390 million
nual
in 2050. Ethiopia, with about 18 million people 50 years ago, is likely
t of
to grow nearly eightfold over a century. In many of these countries,
hil-rapid population growth is a serious problem. Bangladesh, about the size of Iowa, is already overcrowded at 162 million people. If rising ion sea levels flood one-third of the country by 2050, as some climatologists predict, adding even more people could be disastrous.The other demographic world is made up of the richer countries of North America, western Europe, Japan, Australia, and
•ed
New Zealand. This world is wealthy, old, and mostly shrinking.
ti-
Italy, Germany, Hungary, and Japan, for ​all Population density in persons per square kilot 127 million residents ​is expected to shrink to about 100 mil-low of 49 years in 2002; access to antiretroviral treatment has helped survival rates increase since then. The world's highest rate is in Swaziland, where 26.5 percent of adults are living with HIV/AIDS.
The net effect of these variations in growth include high population numbers and densities in China, South Asia, and Europe (figure 7.10). Many areas of high population density are in the fertile river valleys of the Nile, Ganges, Yellow, Yangtze, and Rhine Rivers, and the well-watered coastal plains of India, China, and Europe.
Lower populations occur where resources are limited, as in the high Arctic, or the deserts of Australia, North Africa, and Central Asia.
The most common demographic statistic of fertility is usually the crude birth rate, the number of births in a year per thousand persons. It is statistically "crude" in the sense that it is not adjusted fo population characteristics such as the number of women of reproductive age.
The total fertility rate is the number of children born to an average woman in a population during her entire reproductive life. Upper-class women in seventeenth- and eighteenth-century England, whose babies were given to wet nurses immediately after birth and who were expected to produce as many children as possible, sometimes had 25 or 30 pregnancies. The highest recorded total fertility rates for working-class people is among some Anabaptist agricultural groups in North America, who have averaged up to 12 children per woman. In most tribal or traditional societies, food shortages, health problems, and cultural practices limit total fertility to about six or seven children per woman even without modern methods of birth control.
Zero population growth (ZPG) occurs when births plus immigration in a population just equal deaths plus emigration. It takes several generations of replacement level fertility (where peos ple just replace themselves) to reach ZPG. Where infant mortality rates are high, the replacement level may be five or more children a per couple. In the more highly developed countries, however, this rate is usually about 2.1 children per couple, because some people are infertile, have children who do not survive, or choose not to have children.
As has been the case in Brazil, fertility rates have declined dramatically in every region of the world except Africa over the past 50 years (fig. 7.11). In the 1960s, total fertility rates above 6 were common in many countries. The average family in Mexico in 1975, for instance, had seven children. By 2010, however, the average Mexican woman had only 2.3 children. Similarly, in
Iran, total fertility fell from 6.5 in 1975 to 2.04 in 2010. According to the World Health Organization, 100 out of the world's 220 countries are now at or below a replacement rate of 2.1 children per couple, and by 2050 all but a few of the least-developed countries are expected to have reached that milestone. For many of these countries, population growth will continue for a generation because they have such a large number of young people Brazil, for example, now has a fertility rate of only 1.8 children
0.1
per woman. But 26 percent of its population is under 14 years.
han«
Those children will mature and start to have families before their parents and grandparents die, so the population will continue
of i'
to grow for a few decades. Demographers call this population momentum.
Some of the greatest fertility reduction has been in East Asia.
China's one-child-per-family policy, for example, decreased the fertility rate from 6.5 in 1970 to 1.3 in 2015 (see What Do You Think? later in this section). But as a result of selective abortions for girls (who are less valued in Chinese society), China now reports that 119 boys are being born for every 100 girls. Normal ratios would be about 105 boys to 100 girls. If this imbalance persists, there will be a shortage of brides in another generation. Inte
estingly, Macao, which is culturally similar to mainland China but hasn't shared its one-child policy, now has a total average fertility rate of only 0.9 and the lowest birth rate in the world.
Although the world as a whole still has an average fertility rate of 2.6, growth rates are now lower than at any time since World War Il. If fertility declines like those in Brazil and China were to )ccur everywhere in the world, global population could begin to lecline by 2050, and might be below 6 billion by 2150. Most of Europe now has fertility levels of 1.2 children per woman. Iterestingly, Spain and Italy, although predominantly Roman atholic like Brazil, have below replacement fertility rates.
Although the world as a whole still has an average fertility rate of 2.6, growth rates are now lower than at any time since World War Il. If fertility declines like those in Brazil and China were to )ccur everywhere in the world, global population could begin to lecline by 2050, and might be below 6 billion by 2150. Most of Europe now has fertility levels of 1.2 children per woman. Iterestingly, Spain and Italy, although predominantly Roman atholic like Brazil, have below replacement fertility rates.




dramatically in every region of the world except Africa over the past 50 years (fig. 7.11). In the 1960s, total fertility rates above 6 were common in many countries. The average family in Mexico in 1975, for instance, had seven children. By 2010, however, the average Mexican woman had only 2.3 children. Similarly, in
Iran, total fertility fell from 6.5 in 1975 to 2.04 in 2010. According to the World Health Organization, 100 out of the world's 220 countries are now at or below a replacement rate of 2.1 children per couple, and by 2050 all but a few of the least-developed countries are expected to have reached that milestone. For many of these countries, population growth will continue for a generation because they have such a large number of young people




per square kilometer.

population characteristics such as the number of women of reproductive age.
The total fertility rate is the number of children born to an average woman in a population during her entire reproductive life. Upper-class women in seventeenth- and eighteenth-century England, whose babies were given to wet nurses immediately after birth and who were expected to produce as many children as possible, sometimes had 25 or 30 pregnancies. The highest recorded total fertility rates for working-class people is among some Anabaptist agricultural groups in North America, who have averaged up to 12 children per woman. In most tribal or traditional societies, food shortages, health problems, and cultural practices limit total fertility to about six or seven children per woman even without modern methods of birth control.
Zero population growth (ZPG) occurs when births plus immigration in a population just equal deaths plus emigration. It takes several generations of replacement level fertility (where peos ple just replace themselves) to reach ZPG. Where infant mortality rates are high, the replacement level may be five or more children a per couple. In the more highly developed countries, however, this rate is usually about 2.1 children per couple, because some people are infertile, have children who do not survive, or choose not to have children.
As has been the case in Brazil, fertility rates have declined


dramatically in every region of the world except Africa over the past 50 years (fig. 7.11). In the 1960s, total fertility rates above 6 were common in many countries. The average family in Mexico in 1975, for instance, had seven children. By 2010, however, the average Mexican woman had only 2.3 children. Similarly, in
Iran, total fertility fell from 6.5 in 1975 to 2.04 in 2010. According to the World Health Organization, 100 out of the world's 220 countries are now at or below a replacement rate of 2.1 children per couple, and by 2050 all but a few of the least-developed countries are expected to have reached that milestone. For many of these countries, population growth will continue for a generation because they have such a large number of young people
traveler to a foreign country once asked a local resident, "What's the death rate around here?" "Oh, the same as anywhere," was the eply, "about one per person."In demographics, however, crude death rates (or crude mortality rates) are expressed in terms of the number of deaths per thousand persons in any given year. Countries in Africa where health care and sanitation are limited may have mortality rates of 20 or more per 1,000 people. Wealthier countries generally have mortality rates around 10 per 1,000. The number of deaths in a population is sensitive to the age structure of the population. Rapidly growing, developing countries such as Brazil have lower crude death rates (4 per 1,000) than do the more-developed, slowly growing countries, such as Denmark (12 per 1,000). This is because there are proportionately more children and fewer elderly people in a rapidly growing country than in a more slowly growing one.
Crude death rate subtracted from crude birth rate gives the natural increase of a population. We distinguish natural increase 2050 from the total growth rate, which includes immigration and emigration, as well as births and deaths. Both of these growth rates are usually expressed as a percentage (number per hundred people) rather than per thousand. A useful rule of thumb is that if has you divide 70 by the annual percentage growth, you will get the a, approximate doubling time in years. Niger, for example, which is growing 3.4 percent per year, is doubling its population every 20 years. The United States, which has a natural increase rate of 0.6 percent per year, would double, without immigration, in ten 116.7 years. Belgium and Sweden, with natural increase rates of
0.1 percent, are doubling in about 700 years. Ukraine, on the other
rs.
3ir hand, with a growth rate of -0.2 percent, will lose about 20 percent of its population in the next 50 years. The world growth rate is now 1.08 percent, which means that the population will double in about 66 years if this rate persists.


death rates (or crude mortality rates) are expressed in terms of the number of deaths per thousand persons in any given year. Countries in Africa where health care and sanitation are limited may have mortality rates of 20 or more per 1,000 people. Wealthier countries generally have mortality rates around 10 per 1,000. The number of deaths in a population is sensitive to the age structure of the population. Rapidly growing, developing countries such as Brazil have lower crude death rates (4 per 1,000) than do the more-developed, slowly growing countries, such as Denmark (12 per 1,000). This is because there are proportionately more children and fewer elderly people in a rapidly growing country than in a more slowly growing one.
Crude death rate subtracted from crude birth rate gives the natural increase of a population. We distinguish natural increase 2050 from the total growth rate, which includes immigration and emigration, as well as births and deaths. Both of these growth rates are usually expressed as a percentage (number per hundred people) rather than per thousand. A useful rule of thumb is that if has you divide 70 by the annual percentage growth, you will get the a, approximate doubling time in years. Niger, for example, which is growing 3.4 percent per year, is doubling its population every 20 years. The United States, which has a natural increase rate of 0.6 percent per year, would double, without immigration, in ten 116.7 years. Belgium and Sweden, with natural increase rates of
0.1 percent, are doubling in about 700 years. Ukraine, on the other
rs.
3ir hand, with a growth rate of -0.2 percent, will lose about 20 percent of its population in the next 50 years. The world growth rate is now 1.08 percent, which means that the population will double in about 66 years if this rate persists.
40​Environmental Science​

death rates (or crude mortality rates) are expressed in terms of the number of deaths per thousand persons in any given year. Countries in Africa where health care and sanitation are limited may have mortality rates of 20 or more per 1,000 people. Wealthier countries generally have mortality rates around 10 per 1,000. The number of deaths in a population is sensitive to the age structure of the population. Rapidly growing, developing countries such as Brazil have lower crude death rates (4 per 1,000) than do the more-developed, slowly growing countries, such as Denmark (12 per 1,000). This is because there are proportionately more children and fewer elderly people in a rapidly growing country than in a more slowly growing one.
Crude death rate subtracted from crude birth rate gives the natural increase of a population. We distinguish natural increase 2050 from the total growth rate, which includes immigration and emigration, as well as births and deaths. Both of these growth rates are usually expressed as a percentage (number per hundred people) rather than per thousand. A useful rule of thumb is that if has you divide 70 by the annual percentage growth, you will get the a, approximate doubling time in years. Niger, for example, which is growing 3.4 percent per year, is doubling its population every 20 years. The United States, which has a natural increase rate of 0.6 percent per year, would double, without immigration, in ten 116.7 years. Belgium and Sweden, with natural increase rates of
0.1 percent, are doubling in about 700 years. Ukraine, on the other
rs.
3ir hand, with a growth rate of -0.2 percent, will lose about 20 percent of its population in the next 50 years. The world growth rate is now 1.08 percent, which means that the population will double in about 66 years if this rate persists.

death rates (or crude mortality rates) are expressed in terms of the number of deaths per thousand persons in any given year. Countries in Africa where health care and sanitation are limited may have mortality rates of 20 or more per 1,000 people. Wealthier countries generally have mortality rates around 10 per 1,000. The number of deaths in a population is sensitive to the age structure of the population. Rapidly growing, developing countries such as Brazil have lower crude death rates (4 per 1,000) than do the more-developed, slowly growing countries, such as Denmark (12 per 1,000). This is because there are proportionately more children and fewer elderly people in a rapidly growing country than in a more slowly growing one.
Crude death rate subtracted from crude birth rate gives the natural increase of a population. We distinguish natural increase 2050 from the total growth rate, which includes immigration and emigration, as well as births and deaths. Both of these growth rates are usually expressed as a percentage (number per hundred people) rather than per thousand. A useful rule of thumb is that if has you divide 70 by the annual percentage growth, you will get the a, approximate doubling time in years. Niger, for example, which is growing 3.4 percent per year, is doubling its population every 20 years. The United States, which has a natural increase rate of 0.6 percent per year, would double, without immigration, in ten 116.7 years. Belgium and Sweden, with natural increase rates of
0.1 percent, are doubling in about 700 years. Ukraine, on the other
rs.
3ir hand, with a growth rate of -0.2 percent, will lose about 20 percent of its population in the next 50 years. The world growth rate is now 1.08 percent, which means that the population will double in about 66 years if this rate persists.
Among humans, the oldest living person whose birth was documented was Jeanne Louise Calment of Arles, France, who was
122 years old at her death in 1997. The aging process is still a medical mystery, but it appears that cells in our bodies have a limited ability to repair damage and produce new components. At some point, they simply wear out, and we fall victim to disease, degeneration, accidents, or senility.
Obviously, most people don't reach the maximum age, so usually we examine life expectancy, the average age that a newborn infant can expect to attain.Most of human history life expectancy was 30.Declining morality rise of population in past 300 years death rates started falling in the 1700s in Europe because of better food and sanitation.Life expands has gone up especially in developing countries.India 1900 a man would live for 23 years.Century later India has low per capital income 3,500 U.S. but average life expectancy has tripled almost as much as countries 10 times its income level.Longer life's in Europe because better nutrient,improve sanitation, clean water and education. Large discrepancies exist within countries. In the United
States, for example, while the nationwide average life expectancy
fin


is 77.5 years, Asian American women in Bergen County, New
YOI
Jersey, can expect to live 91 years, while Native American men
the
on the Pine Ridge Reservation in South Dakota are reported to
in j
typically live only to 48. Two-thirds of African countries have life
per
expectancies greater than that on Pine Ridge.
cati
Women almost always have higher life expectancies than
abr
men. Worldwide, the average difference between sexes is three
cor
years, but in Russia the difference between men and women is
14 years. Is this because women are biologically superior to men,
rep
and thus live longer? Or is it simply that men are generally employed
has
in more hazardous occupations and often engage in more danger-
has
ous behaviors, such as drinking, smoking, or reckless driving?
por
As figure 7.12 shows, life expectancy tends to increase with
ger
annual income up to about (U.S.) $10,000 per person. Beyond that
old
level—which is generally enough for adequate food, shelter, and sanitation for most people—life expectancies level out at about
bet
75 years for men and 85 for women.
tha
Some demographers believe that life expectancy is approach-
wh
ing a plateau, while others predict that advances in biology and medicine might make it possible to live 150 years or more. If our
grc tod
average age at death approaches 100 years, as some expect, soci-
of
ety will be profoundly affected. In 1970, the median age in the
In
United States was 30. By 2100, the median age could be over 60.
If workers keep retiring at 65 half the population could be unemployed and retirees could face 35 to 40 years of retirement.


10
Annual per capita Gross National Product (thousands of U.S.

FIGURE 7.12 As incomes rise, so does life expectancy—up to about
(U.S.) $10,000. Above that amount, the curve levels off. Some countries such as South Africa and Russia, have far lower life expectancies than th GDP would suggest. Jordan, on the other hand, which has only one-fifth t per capita GDP of the United States, has a the same life expectancy.
Source: C/A Factbook, 2009
population that is growing rapidly by natural increase has more
New
young people than does a stationary population. One way to show
tn men
these differences is to graph age classes in a histogram, as shown
rted to
in figure 7.13. In Niger, which is growing at a rate of 3.4 percent
ve life
per year, 49 percent of the population is in the prereproductive category (below age 15). Even if total fertility rates were to fall
than
abruptly, the total number of births, and population size, would
three
continue to grow for some years as these young people enter
en is
reproductive age.
men,
By contrast, a country with a stable population, like Sweden,
oyed
has nearly the same number in each age cohort. A population that
tger-
has recently entered a lower growth rate pattern, such as Singapore, has a bulge in the age classes for the last high-birth-rate
vith
generation. Notice that there are more females than males in the
hat
older age group in Sweden because of differences in longevity
Ind
between the sexes.
)tlt
The greatest challenge to slowing population growth may be
that policymakers are not sure how to keep economies growing
​when populations shrink. Contrary to Malthus' prediction that
rd​growing populations deplete resources (section 7.2), economists worry about dependency ratios the number of non working compared to working in population. In the United States, by contrast, a declining working population is now supporting an ever larger number of retired persons and there are debates about how well the social security system will hold up. This changing age structure and shifting dependency ratio are occurring worldwide (fig. 7.14). The UN predicts that by 2050 there will be two older persons for every child in the world. Many countries are rethinking their population policies and beginning to offer incentives for marriage and child-bearing.
Humans are highly mobile, so emigration and immigration play a larger role in human population dynamics than they do in those of many species. Currently, about 800,000 people immigrate legally to the United States each year, and many more enter
Western Europe is particularly stressed by millions of refugees from economic chaos and wars in the Middle East and former socialist states. The United Nations High Commission on Refugees reported in 2016 that 60 million people had been forced from their homes by religious, political, or economic forces. About half had crossed international borders, while the rest were displaced in their own countries. This crisis may become immeasurably worse in coming decades as climate change makes conditions unbearable for billions of people.Developed nations are expected to get 2 million new residents per year for 50 years.
population of the wealthiest countries would already be declining and would be more than 126 million less than the current 1.2 billion by 2050. In 2008, nearly 45.5 million U.S. residents (15.2 percent of the total population) classified themselves as Hispanic or Latino. They now constitute the largest U.S. minority
Immigration is a controversial issue in many countries. "Guest workers" often perform heavy, dangerous, or disagreeable work that citizens are unwilling to do. Many migrants and alien workers are of a different racial or ethnic background than the majority in their new home. They generally are paid low wages and given substandard housing, poor working conditions, and few rights. Local residents often complain, however, that immigrants take away jobs, overload social services, and ignore established rules of behavior or social values. Anti-immigrant groups are springing up in many rich countries.
Some nations encourage, or even force, internal mass migrations as part of a geopolitical demographic policy. In the 1970s, Indonesia embarked on an ambitious "transmigration" plan to move 65 million people from the overcrowded islands of Java and
Bali to relatively unpopulated regions of Sumatra, Borneo, and New Guinea. Attempts to turn rainforest into farmland had disastrous environmental and social effects, however, and this plan was greatly scaled back. China has announced a plan to move up to 100 million people to a sparsely populated region along the Amul River in Heilongjang. By some estimates, more than 250 milli0i internal migrants in China have moved from rural areas to the cil ies to look for work, and another quarter of a billion are expecte to do so in the next few decades.
Improving education for women and personal freedom.When have choice women only wants 2 to 3 babies.Decline in childbearing and later marriages when women have other opportunities.Women salary important to family.Poor countries rising income results in more children briefly. Birthrates in the U.S. have responded to a sariety of historical events, but in general they fell between 1910 and 2010 (fig. 7.16). The period between 191() and 1930 was a time of industrialization and urbanization. Women were getting more education than ever before and entering the workforce. As was the case in Brazil half a century later, birth rates fell. Births increased at the beginning of World War Il (as is often the case in wartime). For reasons that are unclear, a higher percentage of boys are usually born during war years.
At the end of the war, there was a "baby boom" as couples were reunited and women were encouraged to leave work outside the home. This high birth rate persisted through the times of prosperity and optimism of the 1950s, but began to fall in the 1960s. Part of this decline was caused by the small number of babies born in the 1930s. This meant fewer young adults to give birth in the 1960s. As in Brazil more recently, part of this was due to change )erceptions of the ideal family size. Whereas in the 1950s wome ypically wanted four children or more, in the 1970s the nor ropped to one or two (or no) children. A small "echo boo ccurred in the 1980s as people born in the 1960s began to ha abies, but changing economics and attitudes seem to have per altered our view of ideal family size in the United States
Most European countries now have birth rates of 1.5 or fewer children per woman, well below the replacement level of 2.1. Italy,
Russia, Austria, Germany, Greece, and Spain are experiencing negative rates of natural population change. Families in Japan,
Singapore, and Taiwan have fewer than 1.3 children and are also facing a "child shock" as fertility rates have fallen. There are concerns in these countries that declining populations will be unable to maintain military strength (lack of soldiers), economic power (lack of workers and of consumers), and social systems (not enough workers and taxpayers) if low birth rates persist or are not balanced by immigration. Some analysts now emphasize that the United States and Northern Europe are fortunate to have an influx of immigrants, who bring youth, energy, and consumers to shore up the economy.
Economist Ben Wattenberg warns that this "birth dearth" might seriously erode the powers of Western democracies in world affairs. He points out that Europe and North America accounted for 22 percent of the world's population in 1950. By the 1980s, this number had fallen to 15 percent, and by the year 2030, Europe and North America probably will make up only 9 percent of the world's population. Germany, Hungary, Denmark, and Russia now offer incentives to encourage women to bear children. Japan offers financial support to new parents, and Singapore provides a dating service to encourage marriages among the upper classes as a way of increasing population.
On the other hand, because Europeans and North Americans consume so many more resources per capita than most other people in the world, a reduction in the population of these countries will do more to spare the environment.
Stage I in figure 7.17 represents the conditions in a premodern society. Food shortages, nvalnutrition, lack of sanitation and medicine, accidents. and other hazards generally keep death rates in such a society around 35 per I people. Birth rates arc correspondingly high to keep population densities relatively constant. As economic development brings better jobs, medical care, sanitation, and a gencrally improved standard of living in Stage Il, death rates often fall very rapidly. Birth rates may actually rise at first as more money and better nutrition allow people to have the children they always wanted. Eventually, in a mature industrial economy (Stage Ill), birth rates fall as people see that all their children are more likely to survive and that the whole family benefits from concentrating more resources on fewer children. Note that population continues to grow rapidly during this stage because of population momentum (baby boomers reaching reproductive age). Depending on how long it takes to complete the transition, the population may go through one or more rounds of doubling before coming into balance again.
Stage IV in figure 7.17 represents conditions in developed countries, where the transition is complete and both birth rates and death rates arc low, often a third or less than those in the predevelopment cra. The population comes into a new equilibrium in this phase, but at a much larger size than before. Most of the countries of northern and western Europe went through a demographic transition in the nineteenth or early twentieth century similar to the curves shown in this figure.
Many of the most rapidly growing countries in the world, such as Kenya, Yemen, Libya, and Jordan, now arc in Stage I of this demographic transition. Their death rates have fallen close to the rates of the fully developed countries, but birth rates have not fallen correspondingly. In fact, both their birth rates and total population are higher than those in most European countries when industrialization began 3()0 years ago. The large disparity between birth and death rates means that many developing countries now are growing at 3 to 4 percent per year. Such high growth rates in developing countries could boost the total world population to 9 billion or more before the end of the twenty-first century. This raises what may be the two most important questions in this entire chapter: Why are birth rates not yet falling in these countries, and what can be done about it?
Four conditions are necessary for a demographic transition to occur: (l) improved standard of living, (2) increased confidence that children will survive to maturity, (3) improved social status of women, and (4) increased availability and use of birth control. As the example of Brazil in the opening case study for this chapter shows, these conditions can be met, even in relatively poor countries.
Some demographers claim that a demographic transition already is in progress in most developing nations. Problems in taking censuses and a normal lag between falling death and birth rates may hide this for a time, but the world population should stabilize sometime in the next century. Some evidence supports this view. As we mentioned earlier in this chapter, fertility rates have fallen dramatically nearly everywhere in the world over the past half century. The U.N. Population Division now reports that half the world's countries are at or below the replacement rate of 2.1 children per couple.
Some countries have had remarkable success in population control. In Thailand, Indonesia, Colombia, and Iran, for instance, total fertility dropped by more than half in 20 years. Morocco, the Dominican Republic, Jamaica, Peru, and Mexico all have seen fertility rates fall betsseen 30 percent and 40 percent in a single generation. In all these countries. the following factors contribute to stabilizing populations: 1

• Growing prosperity and social reforms that accompany development reduce the need and desire for laree families in most countries.
• Technology is available to bring advances to the developing world much more rapidly than was the case a century a20, and the rate of technology transfer is much faster than it was when Europe and North America were developing. Less-developed countries have historic patterns to follow. They i can benefit from our mistakes and chart a course to stability more quickly than they might otherwise do.
Slodern communications (especially television) have caused a revolution of rising expectations that act as a stimulus to spur change and development.
fertility dropped by more than half in 20 years. Morocco, the Dominican Republic, Jamaica, Peru, and Mexico all have seen fertility rates fall betsseen 30 percent and 40 percent in a single generation. In all these countries. the following factors contribute to stabilizing populations: 1

• Growing prosperity and social reforms that accompany development reduce the need and desire for laree families in most countries.
• Technology is available to bring advances to the developing world much more rapidly than was the case a century a20, and the rate of technology transfer is much faster than it was when Europe and North America were developing.

fertility dropped by more than half in 20 years. Morocco, the Dominican Republic, Jamaica, Peru, and Mexico all have seen fertility rates fall betsseen 30 percent and 40 percent in a single generation. In all these countries. the following factors contribute to stabilizing populations: 1

• Growing prosperity and social reforms that accompany development reduce the need and desire for laree families in most countries.
• Technology is available to bring advances to the developing world much more rapidly than was the case a century a20, and the rate of technology transfer is much faster than it was when Europe and North America were developing.


fertility dropped by more than half in 20 years. Morocco, the Dominican Republic, Jamaica, Peru, and Mexico all have seen fertility rates fall betsseen 30 percent and 40 percent in a single generation. In all these countries. the following factors contribute to stabilizing populations: 1

• Growing prosperity and social reforms that accompany development reduce the need and desire for laree families in most countries.
• Technology is available to bring advances to the developing world much more rapidly than was the case a century a20, and the rate of technology transfer is much faster than it was when Europe and North America were developing.
that many of the poorer countries of the world appear to be caught in a ''demographic trap" that prevents them fmmt escaping from the middle phase of the demographic transition. Their populations are

now growing so rapidl​sustainable yield of local forests, y that grasslands, human crodemands exceed the
High resource demands threaten to destroy the resource base, causIng environmental deterioration, economic decline, and political instability. Can these countries escape from this trap and modernize?
Many people argue that the only way to break out of the demographic trap is to immediately and drastically reduce population growth by whatever means are necessary. They argue strongly for birth control education and bold national policies to encourage lower birth rates. Some agree with Malthus that helping the poor will simply increase their reproductive success and further threaten the resources on which we all depend. Author Garret Hardin described this view as lifeboat ethics. "Each rich nation," he wrote, "amounts to a lifeboat full of comparatively rich people.
Phe poor of the world are in other much more crowded lifeboats. I)ntinuously, so to speak, the poor fall out of their lifeboats and wim for a while, hoping to be admitted to a rich lifeboat, or Wein ome other way to benefit from the goodies on board annot risk the safety of all the passengers by helping others in 3ed. What happens if you share space in a lifeboat? The boat is vamped and everyone drowns. Complete justice, complete catas)Phe." How would you respond to Professor Hardin?
A third view is that social justice (a fair share of social benefits for everyone) is the key to successful demographic transitions.
The world has enough resources for everyone, but inequitable social, political, and economic systems cause uneven distributions
of those resources. As a consequence, hunger, poverty, violence, environmental degradation, and rapid population growth continue. In this view, it is justice and access, not resources, that are limited. Although overpopulation exacerbates other problems, a narrow focus on this factor alone encourages racism and hatred of the poor. A solution for all these problems is to reduce poverty and inequity, not to blame the victims. Small nations and minorities often regard calls for population control as a form of genocide. Figure 7.18 expresses the opinion of many people in less-developed countries about the relationship between resources and population.
An important part of this view is that many of the rich countries are, or were, colonial powers, while the poor, rapidly growinc countries were colonies. The wealth that paid for and security for developed countries was often extracted from colonies, which now suffer from exhausted resources, exploding populations. and chaotic political systems. Some of the world's poorest countries, such as India, Ethiopia, Mozambique, and Haiti, had rich resources and adequate food supplies before they were impoverished by colonialism. Those of us who now enjoy abundance may need to help the poorer countries not only as a matter of justice but because we all share the same environment.
In addition to considering the rights of fellow humans, we should also consider those of other species. Rather than ask what is the maximum number of humans that the world can possibly support, perhaps we should think about the needs of other creatures. As we convert natural landscapes into agricultural or industrial areas, species are crowded out that may have just as much right to exist as we do. What do you think would be the optimum number of people to provide a fair and decent life for all humans while causing the minimum impact on nonhuman neighbors?


had rich resources and adequate food supplies before they were impoverished by colonialism. Those of us who now enjoy abundance may need to help the poorer countries not only as a matter of justice but because we all share the same environment.
pportunities for education and paying jobs are critical factors in​the
fertility rates (fig. 7.19). Child survival also is crucial in stabilizing population. When infant and child mortality rates are high, as they are in much of the developing world, parents tend to have high numbers of children to ensure that some will survive to adulthood.
cas

far th
There has never been a sustained drop in birth rates that was not first preceded by a sustained drop in infant and child mortality. One of the most important distinctions in our demographically divided world is the high infant mortality rates in the less-developed countries. Better nutrition, improved health care, simple oral rehydration therapy, and immunization against infectious diseases (see chapter 8) have brought about dramatic reductions in child mortality rates, which have been accompanied in most regions by falling birth rates. It has been estimated that saving 5 million children each year from easily preventable communicable diseases would avoid 20 or 30 million extra births.
Increasing family income does not always translate into better welfare for children, because in many cultures men control most financial assets. Often, the best way to improve child survival is to ensure the rights of mothers. Land reform, political rights, opportunities to earn an independent income, and the improved health status of women often are better indicators of total fertility and fanlily welfare than rising GNP.

status of women often are better indicators of total fertility and fanlily welfare than rising GNP.
Family planning allows couple number and spacing of their children. It doesn't necessarily mean fewer children—people may use family planning to have the maximum number of children possible—but it does imply that the parents will control their reproductive lives and make rational, conscious decisions about how many children they will have and when those children will be born, rather than leaving it to chance. As the desire for smaller families becomes more common, birth control becomes an essential part of family planning in most cases. In this context, birth control usually means any method used to reduce births, including abstinence, delayed marriage, contraception, methods that prevent the implantation of embryos, and induced abortions. As the opening case study in this chapter shows, there are many ways to encourage family planning.
Humans have always regulated fertility. Evidence suggests that people in every culture and every historic period have used a variety of techniques to control population size. Studies of hunting and gathering people, such as the !Kung or San of the Kalahari Desert in southwest Africa, indicate that our early ancestors had stable population densities, not because they killed each other or starved to death regularly, but because they controlled fertility.
For instance, San women breast-feed children for three or four years. When calories are limited, lactation depletes body fat stores and suppresses ovulation. Coupled with taboos against intercourse while breast-feeding, this is an effective way of spacing children. Other ancient techniques to control population size include abstinence, folk medicines, abortion, and infanticide. We may find some or all of these techniques unpleasant or morally unacceptable, but we shouldn't assume that other people are too ignorant or too primitive to make decisions about fertility.
Modern medicine gives us many more options for controlling fertility than were available to our ancestors. More than 100 new
approved five new birth control products.o 10 Four of these use various methods to administer female hormones that prevent pregnancy.
Other methods are years away from use, but take a new direction entirely. Vaccines for women are being developed that will prepare the immune system to reject the hormone chorionic gonadotropin, which maintains lining and allows egg implant, or that will cause an immune reaction against sperm. Injections for men are focused on reducing sperm production, and have proven effective in mice. Without a doubt, the contemporary couple has access to many more birth control options than their grandparents


tion approved five new birth control products.o 10 Four of these use various methods to administer female hormones that prevent pregnancy.
Other methods are years away from use, but take a new direction entirely. Vaccines for women are being developed that will prepare the immune system to reject the hormone chorionic gonadotropin, which maintains the uter-

contraceptive methods are now being studied, and some appear to have great promise. Nearly
13
all are biologically based (e.g., hormonal)
12
rather than mechanical (e.g., condom, IUD). Recently, the U.S. Food and Drug Administra-
11
ine lining and allows egg implant, or that will cause an immune reaction against sperm. Injections for men are focused on reducing sperm production, and have proven effective in mice. Without a doubt, the contemporary couple has access to many more birth control options than their grandparents had.