Human Population Has Shaped the World Far More than Anything You Learned in History Class

A review of The Human Tide, by Paul Morland

So far this blog has only been about genetics and genealogy. But now I’m going to do something slightly different. I suppose my interests haven’t been entirely unrelated to human population. I’ve read books like Humans, Who We Are and How We Got Here by David Reich, which is about ancestral human populations. I read a couple of paleo-anthropology books by Richard Leakey decades ago. However, I didn’t anticipate a few months ago that I would be reading a book purely about contemporary human population.

I found The Human Tide on the shelf at the library, read the summary on the inside of the dust jacket, and couldn’t resist diving in to the rest. I’m sure it could be very useful as reference material, but I was fascinated enough to read it straight through. While I thought I knew a little something about history, the main effect of this book was to show me that I was unaware of the most fundamental paradigm that has shaped the modern world. Human population has been far more important than I ever could have imagined, and I actually thought it was pretty important beforehand.

Morland does a great job of condemning atrocities and advocating for equal rights from the very beginning and throughout the book. But, primarily, The Human Tide is about human demographics, which, in theory, could be studied in the complete absence of politics, and would still be very interesting.

The human tide is something we missed — it’s almost done happening. (I’d say we’re about eight-elevenths of the way there.) It’s a scientific phenomenon — an emergent behavior — that doesn’t owe itself to any one culture or place, as Morland correctly points out. The book traces population explosions from where they first began (England) to where they have only just begun to occur (sub-Saharan Africa), covering the whole world in the process. There were many interesting tidbits along the way. At the beginning, for example, we’re told that life expectancy is shorter for males in Glasgow than it is in Gaza. And that the death rate is lower in Iraq than in the UK (because of the youthfulness of the former’s population).

Some phenomena that one might not anticipate become apparent from the study of demographics. For example, after a population explosion, a population will be quite young. Even if the birth rate goes down drastically, as is usually the case, the population can still increase for decades. The demographics are riding an initial wave because there are far more people of childbearing age. Conversely, in a greying population, nothing could cause a quick increase in population, save for a lot of immigration. There just aren’t enough people of childbearing age to cause a significant increase relative to the size of the existing population.

Other phenomena give insight into human behavior. For example, there’s a good indicator of unequal opportunity for women in the workplace, despite being in developed nations in which women are as educated or even more educated than men. In this type of country, such as Italy, Spain, or Japan, the fertility rate is often below replacement level. It comes down to the fact that women have aspirations, education, knowledge of a better life, but their governments have neglected their desire to have a good career, especially one that’s balanced with benefits such as childcare and parental leave. A woman who has unfulfilled career ambitions will tend to wait longer to have children, and often that will result in a woman having no children at all, or at least fewer.

Throughout the book, the theme remains constant: populations are initially caught in a Malthusian trap and then undergo what’s called the demographic transition, which begins as a rapid increase in population, caused primarily by decreased infant mortality, but also an increase in overall life expectancy. It isn’t caused by an increase in birth rates, as they would have been high before the increase in population. The birth rate eventually falls, but the population is so young that the birth rate remains high for an extended period of time. Along with this, the demographic transition will have caused an increase in the quality of life. In every case, the end result has been reduced fertility to replacement level or below, which, depending on the death rate in a population, is usually about 2.1 children per woman. Populations end up much higher than before a demographic transition, but falling or stable and sometimes buoyed up by immigration.

It started in England just before the year 1800. Nobody is sure exactly why England was first, but it’s known that there’s a positive feedback between industrial growth and population. It seems simple, then, that England was where industry first reached a threshold above which that feedback could start occurring. The economic development led to an increase in population, which provided more workers for industry. The biggest driver of population growth is falling infant mortality. This has a huge effect on the number of people who will be of childbearing age in the near future. Surely, the positive feedback with industry isn’t the only cause of the demographic transition. It was also necessary to have some minimum standard of sanitation and health care, which weren’t great at that time, but the efforts that were made were enough to cause a decrease in infant mortality and eventually an increase in overall life expectancy. England wasn’t the only place that met the minimum standard of health and sanitation, but it was the first place to meet all of the necessary conditions for a demographic transition.

With just the right conditions met, the people of the British Isles were about to change the world. Not only did their population explode in a way that the world had never seen, they managed to populate the U.S., Canada, South Africa, Australia, and New Zealand with numbers that dwarfed those of the natives who lived in each of those places. Reactionaries would be quick to say that that shifts the blame to population rather than atrocities carried out by colonizers. But it only means that the demographics allowed Britain to colonize several parts of the globe, not that it had to. An increase in population may have put pressure on Britons to emigrate, but it by no means dictates what they do after they leave home.

While Britain’s population was rapidly rising, nations like Spain, France, and Italy that had colonial aspirations of their own were not able to populate continents to any great extent. Whether the reason was more knowledge about birth control or an insufficient economic engine to be used as a positive feedback, the populations of Spain, France, and Italy remained relatively constant compared to Britain’s. When England fought the Spanish Armada, Spain had twice the population of Britain. After Britain’s demographic transition, it had twice the population of Spain.

Morland points out that each nation that underwent a demographic transition did so more quickly than those before it. The increase in population was quicker and higher in magnitude, and the subsequent crash in fertility rates occurred faster. After Britain, the next place with a population explosion was Germany. Its population has always been larger than the UK’s, but the balance of power had shifted much more to the favor of England in the 19th century, especially as Germany had not yet unified at that time. Germany’s population explosion was so large that it allowed it to try taking over the world on two occasions. And it likely would have succeeded if it wasn’t for the demographic transition of the next countries in line.

It isn’t exactly clear to me from reading the book where the U.S. fits into this timeline. One thing Morland notes is that Germany’s population was three-quarters of that of the U.S. at the turn of the twentieth century and was less than half by World War II. Using other sources, it looks to me like the rise in population in the U.S. occurred roughly along the same timeline as that in Germany. The striking difference between the two is that, while Germany’s population began to level off around 1910, and while the U.S. population growth rate started declining in the 1920s, total population in the U.S. continued to increase well into the 2000s, probably because of immigration and the size of the U.S. It might not always be easy for the U.S. to attract working-age immigrants, however. Although one might not guess based on media coverage or the way in which Donald Trump kicked off his 2016 presidential campaign, it’s worth noting that, since about 2012, more Mexicans have been returning to Mexico than have been coming to the U.S.

Russia’s population explosion occurred faster and with greater magnitude than Germany’s, just like Germany’s in comparison to England’s. The population of Russia more than quadrupled during the 19th century. In 1905, Russia surprisingly lost its war against Japan, which was far smaller, but it was an indication that Japan was on the rise. Despite that loss, Russia’s demographic transition would serve it well for a considerable amount of time. Germany’s losses in the World Wars surely were due in part to its fighting on two fronts, and in part because of the weather in Russia. But in large part they were also due to the fact that Germany was fighting two demographic giants: the U.S. and Russia (the Soviet Union on the second occasion). Morland relates that while the Germans captured and killed millions from the Red Army in World War II (26 million died by the end of the war), the Russian soldiers just kept coming. Russia’s population explosion allowed it to be one of only two “superpowers” to have ever existed. Today, Russia has a notoriously low life expectancy, and would be among the top countries in the world for population loss if not for immigration.

When England was in the midst of their demographic transition and no other nations had yet joined them, some prominent Britons thought that there was something very special about their race. Later, they feared that it was Germans who had an inherent rigor of fertility in their genes. Eventually, they started calling Russians “Europeans,” albeit very reluctantly, in order to keep making the claim that Europeans had a fundamental advantage over other races. Many cringe-worthy quotes are given in The Human Tide, cementing certain historical figures’ unenviable places for the foreseeable future. It’s funny that it took so long to figure it out — a nation of any race can have a population explosion if the same few conditions are met.

Japan was the next country to drastically change the world with the assistance of its population. The increase was the fastest and most intense yet. One thing that surprised me was that the post-war baby boom that occurred in the U.S. also occurred in every other part of the developed world. It was even higher in Canada than in the U.S. But, like all things demographic, Japan’s baby boom was even more dramatic. Following that, its decrease in population was so precipitous that Japan passed up all other countries in its stage of demographic transition, including those that began long before it. Japan now has the oldest population of any large nation that’s ever existed, with a median age of over 48. Total population peaked around 128 million in 2010, but may fall to two-thirds of that by 2050. Many seniors, many who don’t have children, don’t interact with other humans on a regular basis, as proven by the fact that bodies are sometimes found weeks after a person has died. Robots are now being used to care for the elderly. Japan has eight million empty homes and some suburbs are almost completely abandoned. There are several countries that should be watching Japan very closely, as they will be experiencing the same demographic problems in the future.

China had some early fits and starts to population growth, constrained by famines, epidemics, and wars. It began to increase at least by the mid-nineteenth century, already reaching 430 million by that time. China is infamous for its attempts to manipulate birth rates.

There’s new evidence that Chinese individuals had been managing their population for a long time, minimizing suffering by keeping the population below the Malthusian maximum. Unfortunately, since there was likely no birth control, this was done through infanticide. Today, in all places where the demographic transition has run its course, there are people who choose birth control as a far more preferable option to avoid resource constraints and pursue the lifestyles they envision.

Few of the programs put into place by governments to change population have ever caused the intended effect, but most have had disastrous consequences. The policies of Indira Ghandi and her son led to the sterilization of over six million men and five million women in India. Both China and the Soviet Union had conflicts or changes over time in government policies regarding population. In The Human Tide I learned that Karl Marx believed it was actually impossible for a human population to ever outgrow its resources. No matter how large a population and no matter how small the resources, socialism would be able to provide untold bounty to whatever human population exists. Initially, policies in China were relics of this idea. Lenin, however, believed that a lower birth rate would alleviate suffering and allow more equality for women. The Soviet Union was the first country in the world to legalize abortion. Stalin was worried about too low of a population and abortion was made illegal again. The policy reversal seems to have caused no effect, however. Fertility rates continued to fall despite all government efforts. Eventually, the leaders of both nations realized that the untold bounties had not come. While the Soviet Union had falling fertility rates, the leaders in China realized that they couldn’t provide for the population if it continued to grow at the rate they were seeing.

The Chinese government really began to worry about population growth in 1952. In 1947, population was estimated to be 470 million. Five years later, the census showed a population of 600 million, which probably wasn’t accurate, but real growth was likely huge. It wasn’t until 1980 that the One Child Policy was instituted. The government used methods such as forced abortions and firing offenders from jobs. But fertility rates had been plummeting since 1970 and would have continued doing so without intervention. Similarly, ending the policy in 2015 seems to have caused no change in birth rates. If the One Child Policy did work at all, then it contributed to China’s future problem of a rapidly graying population. And it has definitely resulted in the fact that about 120 Chinese boys are born for every 100 Chinese girls. Besides the fact that government coercion to change fertility rates aren’t effective, the next most instructive lesson from China is that, by the time the government of China reacted to rapidly growing population, the opposite problem was already in effect.

In the near future, India will surpass China as the country with the largest population. Many have fretted about the rise of China on the global stage. They were mostly wrong, as China’s population will soon begin to decline and that will intensify over time. Similarly, India’s population, though still growing, will be set to decline after China’s. Neither will see growth in the near future like what will be experienced in sub-Saharan Africa, the most rapidly growing area in the world.

Growth and subsequent leveling-off of population in southeast Asia has been astonishing. There are now about 800 million people in the countries known as the Asian Six (Indonesia, South Korea, Vietnam, Myanmar, the Philippines, and Thailand) where there had been fewer than 200 million in 1950. According to Morland, Thailand is one of many countries that will likely complete their demographic transition without ever enjoying the economic spoils that once went along with it. Save for South Korea, the Asian Six have been historically very poor, but may be showing signs of economic potential.

The Middle East and North Africa were the next regions to experience high population growth. Yemen illustrates the extent of the population explosion more than any other country in this part of the world, increasing from 7.5 million in 1978 to 25.5 million in 2012. From The Human Tide:

In some years during the 1990s, the population of Yemen was growing at a mind-boggling 5% per annum, a rate at which a population will grow more than one hundredfold in the space of a century. (If Germany were to grow at this rate for a century, for example, then there would be more Germans than there are people in the world today.)

Egypt, with over 100 million people, has the highest population in this part of the world. Once a country with a proclivity for agriculture, it has become reliant on aid from the U.S. This has allowed the population to increase much more than the current economy and agriculture can sustain. As Morland points out, if the U.S. cut off aid to Egypt, tens of millions of Egyptians would likely starve to death or try migrating to places like southern Europe. And, as we’ve seen before, the countries there are often hostile to such immigrants. Similar tragedies would unfold in nearby countries if, for example, oil prices plummeted.

The youthfulness of these regions in the midst of their demographic transitions made them ripe for revolution. The people in these countries certainly had a lot of valid reasons to be upset, but demographics played a huge part in causing the Arab Spring.

The countries within Central and South America have completed their demographic transitions. Mostly, they haven’t seen great economic success while doing so. However, great improvements have been made in life expectancy and literacy. These countries, such as Brazil, will grapple with the effects of a greying population in the same way that Japan and southern Europe have already begun to do.

The last region in this story is sub-Saharan Africa. Nigeria, with over 200 million people, has the largest population in Africa — nearly twice that of Ethiopia, which is second. With mortality rates on the decline, the population of Nigeria will more than quadruple by the end of the century.

You may have noticed that this hasn’t been a story of tragedy. I haven’t mentioned until now that 12 million died due to famine and corruption in the Soviet Union. When tragedies were mentioned, it still wasn’t the main story. This has been a story about the human tide — something beautiful that has lifted up the quality of life for billions of people. Human suffering is terrible and worth volumes of analysis, but that isn’t what The Human Tide is about. Amazingly, all along the way, a lesson from the book is that the demographic transition far outstrips the numbers that can be lost from wars and other atrocities. However, there was an exception to this. I was heartbroken to learn that the number of Jews in the world is still lower than what it was before the Holocaust.

I have a newfound appreciation for the world we live in. In a way, it’s impossible for people to have a grasp of its size, the number of people, the diversity of its people, the way they live out their lives. But I still find it embarrassing how little I knew and how little I still know. One city mentioned in The Human Tide is Lagos, Nigeria. What percentage of people in the U.S. have heard of it? It has more than five times as many people as Los Angeles. The number could easily double or quadruple in the next 50 years. Split evenly between India and China are twelve cities that each have greater populations than Chicago. Who could name all of them? Japan has two cities with higher populations than New York City and a third city with more than Chicago. One can never learn too much about the people with whom we share our planet.

One thing that wasn’t surprising in this book is that societies are becoming more liberal in their attitudes towards sex. Presently, most births in England are to unmarried partners. This, along with more immigration than most western nations, is allowing England to keep its population on a slight increase. When the population problem facing most of the world is how to deal with the economic hardships of a declining population, there are lessons to learn here.

The main story is that the West has had its moment of demographic transition and that sub-Saharan Africa will make up a large part of the discourse in the future. The West enjoyed the splendors and violated a lot of human rights along the way. It would be unfair to say that China or India shouldn’t have had a transition of their own. It would likewise be unfair to say that sub-Saharan Africa shouldn’t enjoy their own demographic transition. Arguments that populations or population growth rates in Africa are too high often come off sounding like nothing more than racism.

All along people have spoken out about their worries that their own race will decline. It is true — the number of white people will decline on every continent for a long time to come. There’s no reasonable way to think about this other than the fact that it’s totally fine. In fact, the population that will someday make up the vast majority of Earth’s ancestors — sub-Saharan Africans — are already the ancestors of all humans living today. They are the most diverse human population on the planet. Each of us is more related to them than to any other race. And there is more diversity between two sub-Saharan Africans than there is between a German and a Korean. There is hardly a human gene outside of Africa that isn’t also found in Africa. For those who have a tendency to generalize people, Africans are the least generalizable. For those who want to preserve any particular race, sub-Saharan Africans are the ones who have the diversity of genes that humans need in order to keep surviving. And that’s a lucky thing because they’re going to enjoy a demographic transition just like the rest of the world has.

In the 19th century, the French thought that they were going to colonize Algeria much in the way that England had done with its colonies, almost completely replacing native populations with those of its own. (Unfortunately, my third great-grandfather was one who was stationed in Algeria in the 1830s, although he tried and probably succeeded in removing himself from there before scheduled.) The French were in for a big surprise. They never had anywhere near the population increase that Britain enjoyed and were thusly thwarted early on in their colonial attempts. They made no impact to speak of on the demographics of Algeria. And, ironically, the people of Algeria and nearby countries will have someday made an enormous impact on the demographics of France. Such is the nature of the demographic transition. As Morland notes, those who go last will be the most plentiful.

Think about all of the scholars who have spent their lives analyzing the reasons that wars happened? How many have dedicated their studies to the Russian Revolution alone? What would their reaction be if they found out that there was a far more important factor than anything they considered? Human population has been more responsible for revolutions than any political factor. In a silly way, this is true by definition, but it’s also true any way you slice it. The truth is that revolutions are far more likely to happen in a population that’s young. It was true in France, the population center of Europe at the time, when life expectancy was under 30. It was true in Russia, that had just come off of the largest population explosion the world had ever seen. And it was true during the Arab Spring.

In Japan, who is supposed to take care of the elderly? Could it be other elderly people, or should all young people be available to take care of them? In the U.S. senior care might not just come down to re-allocating funds to prop up social security funds. Regardless of how much money the government has to pay senior care workers, who will do it? Would you be willing to switch careers? What if it was compulsory? We’d better hope that politicians’ stance on immigration changes, that immigrants are still interested in coming here, and that some are willing to do this kind of work. In the future, the amount of hardship endured from population contraction will depend on the amount of growth that’s occurring now.

I think a very important idea that’s missed (or not hit very hard) in the book is that the Malthusian trap is there for a reason. It really is a resource constraint. And, while Malthus would appear to be wrong for the next 200 years after he came up with his ideas (if one only pays attention to developed nations), the idea that any population is constrained by its resources is not only true, but obvious. That means that whatever the advantage humans have found that allowed them to break out of the Malthusian trap, there’s still a ceiling somewhere. You can claim that space exploration will save us, but we don’t know that. Populations have only broken out of the constraints, historically, when they’ve been able to outsource their agriculture — usually by colonization. At the very end of The Human Tide it’s acknowledged that there has been a significant environmental cost to the demographic transition, that not only is it a function of the quality of life enjoyed by our planet’s inhabitants, but also the sheer number of people. When you’re dealing with numbers like 8–11 billion, that should be obvious. What’s also implied is that a large number of people, each with a high quality of life, will be even worse for the environment. Morland is confident that we can solve these problems with technology. As a person who used to run ocean climate models, I’m not sure I agree, but I do hope that’s true. Really, it’s just a matter of how much destruction we will have done to our environment, not if we will have done damage. And, just maybe, we will eventually learn to live in a non-destructive way. One thing is for certain — for as long as humans exist, human population will be important.

I know that a lot of people don’t think that human population is important, and that it could never be important. That’s ironic, considering that it’s the most important thing to happen to our planet since the atmosphere turned oxygenic. Probably even more people have never seriously considered ideas about human population. I hope that people reading this review will choose to read The Human Tide for themselves. It contains way more information than I could ever report here. If not, I hope that I’ve done it justice by conveying how important human population has been in shaping the world for the past few centuries and how important it will be in the future.

The way birth statistics have been tracked for a long time now has been by compiling statistics for mothers. One could get the same statistics by tracking only fathers, but that would create scores of needless complications, which I probably don’t need to explain. But, for good measure, here are some: It’s much harder to prove paternity, men often haven’t stuck around for child rearing in the past, the statistical spread of ‘children per man’ has historically been much higher than for ‘children per woman,’ and the window of time over which men can have children is far wider, therefore causing much more uncertainty in calculations. With a likely increase in LGBTQ+ rights, conversations, and perhaps individuals themselves, demographic statistics may be reported differently in the future. I welcome changes that will be more inclusive. The sooner the better.

Feel free to ask me about modeling & simulation, genetic genealogy, or genealogical research. And make sure to check out these ranges of shared DNA percentages or shared centiMorgans, which are the only published values that match peer-reviewed standard deviations. That model was also used to make a very accurate relationship prediction tool. Or, try a calculator that lets you find the amount of an ancestor’s DNA you have when combining multiple kits.

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