The World Health Organization (WHO) has stated that the human population on Earth will exceed 8 billion by the end of November, 2022. As of this writing on November 1st, the population is estimated to be between 7,985,000,000 and 7,997,000,000. Every day there are some 368,000 births offset by about 148,000 deaths. The population increases each day by approximately 220,000 people. Thus, by the end of this month, we will add another 6.6 million people to the planet.
Let’s briefly look at how we got to this place and what are some of the implications for global health. Our ancient hominin (human-like) ancestors first evolved from the line of apes and chimpanzees in Africa about 8 million years ago. The oldest hominin fossil dates back 4.2 million years. Modern humans first appear in the fossil record about 300,000 years ago. During this period, there were several different hominin offshoots, some possibly living alongside each other in the same areas. The most famous being the Neanderthals and Cro-Magnon, the latter being modern humans. Modern humans began to migrate out of Africa as the current ice age began to recede around 120,000 years ago. They first appeared on the European continent 35,000 years ago. At that time, much of Europe and North American were still covered in ice. Humans survived totally on hunting and gathering. The number of humans living on the European continent during this time is estimated to not exceed about 10,000 at any one time.
The big change began about 13,000 years ago with the development of agriculture. The cultivation of grains soon led to domestication of animals. Humans began to stay in one place instead of migrating. This allowed for towns and then cities and then kingdoms to develop. The world population at that time was approximately 5 million people. The population slowly grew as humans spread out across the globe in increasing numbers. The overall growth rate was about 0.05%. Over the next 8,000 years, the population only grew to about 200 million.
The Age of Enlightenment, which started with a population of about 610 million, began in the early 17th century. This period saw the foundations of modern science, engineering, and medicine and brought on the subsequent Industrial Revolution. With better techniques of farming and the ability to move food and other resources for long distances, as well as improvements in sanitation and health, the population began to grow rapidly and reached 1 billion for the first time in 1804. The growth rate was now over 1% and this is the start of the exponential growth that we still are experiencing today.
It took 123 years to add another billion to reach 2 billion in 1927, but then only 33 years later it hit 3 billion in 1960. At this time, the growth rate reached a peak of 2%. From then the growth rate started to decline slightly, yet still we hit the fourth billion in just under 15 years in 1974. The growth rate has steadily declined and is now back to about 1% which yielded a world population of 7 billion in 2011. Now we are at 8 billion. At the current rate, the world population will reach 9 billion around 2037 and then 10 billion between 2056 and 2058. It is expected that the growth rate will continue to decline and eventually flatten out by 2100 at a population of about 10.8 billion. However, some estimates place the plateau at 11.2 billion.
There are several reasons for the slowing down of the population growth. The main reason will be an outstripping of the world’s resources available to support further growth. Availability of food and water is likely to get steadily worse as the climate continues to change. Famine and starvation may become a greater challenge. There is expected to be increasing competition for rare minerals and other vital resources. The competition for these resources, along with straining food and water supplies, is likely to increase global instability and conflict.
While the two most populated areas in the world, China and India, both currently have about 1.5 billion people each, they are already reaching maximum capacity. Most of the growth between now and 2050 is expected to occur on the African continent which is already challenged with famine and draught. The United States is the third most populated country with 332 million, but this number is expected to remain relatively stable. Europe, which has about 750 million currently, will see a decline of about 10-15% in its population in large part due to intentional limitation in family size.
Another factor that contributed to the population explosion was the significant improvement in medicine and surgery after World War II. This directly led to an increase in life expectancy in much of the developed world, meaning that more people lived into their 80’s and 90’s. However, the maximum age limit has not changed. Thus, this fueled much of the peak in the growth rate in the 1960s, but its effect is now receding (see the Miller Report of May 23, 2022, to learn more about human longevity).
Policy leaders from both the United Nations and the World Health Organization have met annually starting in 1958 and held an international conference every ten years around the challenges of increasing human population. Interestingly, almost all of that discussion has been around how to accommodate this increasing number of human mouths to feed. There has been little effort to examine strategies to curb the growth before we reach a point where massive famine and starvation place a limit on things. For example, the average number of child births per woman in the world is currently 2.4. If that were to decrease to just 2.1, then overall population growth would become zero. In other words, the number of births would equal the number of deaths and the population would stabilize. If that birth rate was reduced to just 1.5 births per woman, then the population would experience a negative growth which would be manageable and we could potentially avoid some of the global problems we are currently destined to face.
However, cultural, economic, and religious pressures still drive political decision-making away from even having that conversation. Case in point being China’s one-child policy enacted in 1980. There was such international pressure against China on this, particularly from the United States, that China eventually abandoned the policy in 2015, allowing two children per family. Then, in July 2021, this was further relaxed to three children per family. While the Chinese policy was criticized for abuses this led to, it seems that “enlightened” societies should be able to come up with strategies to effectively encourage limiting reproduction while not going to draconian levels.
Currently, we continue to focus our policies in the opposite direction, promoting reproduction. The US economy, for example, is based on population growth fueling new housing construction and automobile manufacturing.
It seems that we are overdue to have the uncomfortable but important discussion on what we want the future of the human race to look like.