5.1: History and Global Distribution
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Introduction
A population is a group of individuals living together in a given area at a given time. Changes in populations are termed population dynamics. The current human population is made up of all of the people who currently share the earth. The first humans walked the planet millions of years ago. Since that time, the number of humans living on the planet and where they live has constantly changed over time. Every birth and death is a part of human population dynamics. Each time a person moves from one location to another, the spatial arrangement of the population is changed, and this, too, is an element of population dynamics. While humans are unique in many ways as a species, they are subject to many of the same limiting forces and unexpected events of all populations of organisms.
In 1999, the human population crossed the six billion mark. In 2010, the human population reached seven billion. In 2022, 8 billion people were declared. At current growth rates, the population will double within 50 years. However, the overall growth rate of humans has slowed. Long ago, when the human population was small, the doubling of the population had little impact on the human population or its environment. However, with the size of today's population, the effect of doubling the population is quite significant. Already, most of the people of the world do not have adequate clean water, food, housing, and medical care, and these deficiencies are at least partially the result of over population. As the population continues to grow, competition for resources will increase. Natural disasters and political conflicts will exacerbate the problems, especially in the more stressed regions of developing nations. The survivors of this competition will likely be determined by factors such as place of birth and educational opportunities.
In this 10-minute video, the following ideas are covered. Is the world overpopulated or underpopulated? While we worry about there being too many people for the planet to support, we can also worry about how fewer people in a given place may affect the economy, what may happen when there are more elderly people who need care than there are healthcare workers, or even be concerned about how many people are necessary to carry on other aspects of culture.
Question after watching: Which ideas follow from the previous unit and which are new to studying human populations?
Population Growth
Human populations are not stagnant. They naturally change in size, density and predominance of age groups in response to environmental factors such as resources availability and disease, as well as social and cultural factors. The increases and decreases in human population size make up what is known as human population dynamics. If resources are not limited, then populations experience exponential growth. A plot of exponential growth over time resembles a "J" curve. Absolute numbers are relatively small at first along the base of the J curve, but the population rapidly skyrockets when the critical time near the stem of the J curve is reached.
For most of the history of modern humans (Homo sapiens), people were hunter-gatherers. Food, especially meat from large mammals, was usually plentiful. However, populations were small because the nomadic life did not favor large family sizes. During those times, the human population was probably not more than a few million worldwide. It was still in the base of the J growth curve.
It's tough to know what happened on Earth thousands of years before anyone started writing anything down. But thanks to the amazing work of anthropologists and paleontologists like those working on National Geographic's Genographic Project, we can begin to piece together the story of our ancestors as this 2.5 minute video explains.
Question after watching: How did humans populate the globe from East Africa?
Watch the human population grow from 1 CE to the present and see projected growth in under six minutes. One dot = 1 million people.
From about 2 million years ago until 13,000 years ago there were several human species inhabiting the earth. In fact, 100,000 years ago there were at least 6 different human species! Today there’s only us: Homo sapiens. In this 5-minute video, we’re going to look at some of the key moments in our population growth, and what the future might look like.
With the end of the last Ice Age, roughly 10,000 years ago, the climates worldwide changed and many large mammals that had been the mainstay of human diet became extinct. This forced a change in diet and lifestyle, from one of the nomadic hunter-gatherer to that of a more stationary agricultural society.
Humans began cultivating food and started eating more plants and less meat. Having larger families was possible with the more stationary lifestyle. In fact, having a large family increasingly became an asset, as extra hands were needed for maintaining crops and homes. As agriculture became the mainstay of human life, the population increased.
As the population increased, people began living in villages, then in towns, and finally in cities. This led to problems associated with overcrowded conditions, such as the buildup of wastes, poverty, and disease. Large families were no longer advantageous. Infanticide was common during medieval times in Europe, and communicable diseases also limited the human population numbers. Easily spread in crowded, rat-infested urban areas, Black Death, the first major outbreak of the Bubonic Plague (1347-1351) drastically reduced the populations in Europe and Asia, possibly by as much as 50 percent.
Starting in the 17th Century, advances in science, medicine, agriculture, and industry allowed rapid growth of human population and infanticide again became a common practice.
The next big influence on the human population occurred with the start of the Industrial Revolution in the late 18th century. With the advent of factories, children became valuable labor resources, thereby contributing to survival, and family sizes increased. The resulting population boom was further aided by improvements in agricultural technology that led to increased food production. Medical advancements increased control over disease and lengthened the average lifespan. By the early 19th century, the human population worldwide reached one billion. It was now in the stem of the J-curve graph. As the world approached the 20th century, the human population was growing at an exponential rate.
U.N. forecasts suggest the world population could hit a peak of 10.1 billion by 2100 before beginning to decline. But exact numbers are hard to come by — just small variations in fertility rates could mean a population of 15 billion by the end of the century. In this 2.5-minute video, learn more.
Question after watching: What factors increased growth the most over the last 200 years?
In this 3-minute video, learn why India and China have so many people today.
Question after watching: What are the factors that have given India and China a head-start on population growth?
During the 20th century, another important event in human population dynamics occurred. The birth rates in highly developed countries decreased dramatically. Factors contributing to this decrease included: a rise in the standard of living, the availability of practical birth control methods, and the establishment of child education and labor laws. These factors made large families economically impractical. In Japan, the birth rate has been so low in recent years that the government and corporations are worried about future labor shortages. Therefore, they are actively encouraging population growth. In contrast, the populations in less well-developed countries continue to soar. Worldwide, the human population currently exceeds eight billion and continues to grow exponentially. How much more the world population will grow is a topic of intense speculation. One thing is certain: exponential growth cannot continue forever, as Earth's resources are limited.
If the population of the world was only 100 people, what would society look like? Find the answers in this short 2.5-minute animation.
Question after watching: What new information did you learn that you did not know about the global population before?
What does the population of the US look like? It might help to shrink it down a bit. This 2.5-minute animation illustrates how the US would break down if it were a village of just 100 people.
Question after watching: Contrast this with the previous video. What are similarities and differences in the US versus global population?
Population Demographics
Human demography (population change) is usually described in terms of the births and deaths per 1000 people. When births of an area exceed deaths, population increases. When the births of an area are fewer than deaths, the population decreases. The annual rate at which the size of a population changes is:
\[\text { Natural Population Change Rate }\% =\dfrac{\text { (Births - Deaths) }}{1000} \times 100\]
During the year 2000, the birth rate for the world was 22 and the death rate was 9. Thus, the world's population grew at a rate of 1.3 percent. The annual rate of population change for a particular city or region is also affected by immigration (movement of people into a region) and emigration (movement out of a region).
\[\text{Population Change Rate}=\left(\begin{array}{c}\text { Birth } \\ \text { rate }\end{array}+\begin{array}{c}\text { Immigration } \\ \text { Change Rate }\end{array}\right)-\left(\begin{array}{c}\text { Death } \\ \text { rate }\end{array}+\begin{array}{c}\text { Emigration } \\ \text { rate }\end{array}\right)\]
Highly industrialized nations, like the United States, Canada, Japan and Germany, generally have low birth and death rates. Annual rates of natural population change vary from -0.1% to 0.5%. In some industrial nations (e.g. Germany and Russia) death rates exceed birth rates so the net population decreases over time. Newly industrialized countries (e.g. South Korea, Mexico and China) have moderate birth rates and low death rates. The low death rates result from better sanitation, better heath care and stable food production that accompany industrialization. The annual rates of natural population change are about 1 percent to 2 percent in these countries. Countries with limited industrial development (e.g. Pakistan and Ethiopia) tend to have high birth rates and moderate to low death rates. These nations are growing rapidly with annual rates of natural population change exceeding 2 percent.
Learn how to calculate growth rate, interpret growth diagrams, survivorship curves, population pyramids (age structures), exponential and logistic growth in this 4.5-minute video!
Several factors influence human fertility. Important factors influencing birth and fertility rates in human populations are: affluence, average marriage age, availability of birth control, family labor needs, cultural beliefs, religious beliefs and the cost of raising and educating children.
The rapid growth of the world's population over the past 100 years mainly results from a decline in death rates. Reasons for the drop in death rates include better nutrition, fewer infant deaths, increased average life span, and improvements in medical technology.
As countries become developed and industrialized, they experience a movement from high population growth to low population growth. Both death and birth rates decline.
These countries usually move from rapid population growth, to slow growth, to zero growth, and finally to a reduction in population. This shift in growth rate with development is called the "demographic transition." Four distinct stages occur during the transition: pre-industrial, transitional, industrial, and post-industrial.
- During the pre-industrial stage, harsh living conditions result in a high birth rate and a high death rate. The population grows very slowly, if at all.
- The transitional stage begins shortly after industrialization. During this phase, the death rate drops because of increased food production and better sanitation and health conditions, but, the birth rate remains high. Therefore, the population grows rapidly.
- During the industrial stage, industrialization is well established in the country. The birth rate drops and eventually approaches the death rate. Couples in cities realize that children are expensive to raise and that having large families restrict their job opportunities.
- The post-industrial stage occurs when the birth rate declines even further to equal the death rate, thus population growth reaches zero. The birth rate may eventually fall below the death rate, resulting in negative population growth.
The United States and most European countries have experienced this gradual transition over the past 150 years. The transition moves much faster for today's developing countries. This is because improvements in preventive health and medical care in recent decades have dramatically reduced mortality -- especially infant mortality -- and increased life expectancy. In a growing number of countries, couples are having fewer children than the two they need to "replace" themselves. However, even if the level of "replacement fertility" were reached today, populations would continue to grow for several decades because of the large numbers of people now entering their reproductive years.
As a result of reduced fertility and mortality, there will be a gradual demographic shift in all countries over the next few decades toward an older population. In developed countries, the proportion of people over age 65 has increased from 8% to 14% since 1950 and is expected to reach 25% by 2050. Within the next 35 years, those over age 65 will represent 30% or more of the population in Japan and Germany. In some countries, the number of residents over age 85 will more than double.