Demography and Destiny

In this essay, I will make the case that demographic transition theory is wrong.

Demographic transition theory (DTT) proposes that people go through a transition from high fertility to low fertility as their societies modernize. Supposedly this will lead to a stable or declining world population at some point in the future. This assumption is built into UN population projections. This theory fits the evidence of recent history. Over the last 100 years, fertility rates have fallen dramatically as modern civilization spread around the world. Today, most parts of the world have low or declining fertility.

What caused this change in human behavior? The generally accepted view is that wealth causes lower fertility, either because poor people have extra children to make up for those that they expect to die young, or because people want children to work on the farm and to care for them in old age. According to this view, people will choose to have fewer children if childhood mortality goes down or if they don’t need children to work on the farm or to support them in old age.

This explanation does not make sense biologically, psychologically or economically. It also doesn’t fit the evidence of history.

It isn’t biologically plausible because life forms are shaped by evolution to reproduce. Thus, abundant food should cause population growth, not population stability or decline. And, that is what we observe in nature. An expansion of the food supply causes population growth for every other species. There is no reason why human beings should be exempt from this general principle.

It isn’t psychologically plausible that people rationally choose to have more children to make up for those that they expect to die. Would you bring more children into the world if you thought they were likely to die young from war, disease or famine? It is also psychologically implausible that parents have children to use as slaves: to work on the farm or to support them in old age. There is a psychological mechanism that causes parents to transfer energy to their children: love. Parents work for their children because they love them.

Also, it does not make biological sense for children to transfer energy to their parents, because that behavior pattern would not improve reproductive fitness, and thus it could not evolve. Biologically, it is a waste of energy to transfer of energy from children to parents instead of vice versa.

Energetically and economically, children are a net cost to their parents, not a net benefit.

Some cultures might have a myth that children are economically beneficial to their parents, but that is only a myth. Such myths exist because they promote reproduction. Beliefs that make people reproduce, even if they are misleading, can be selected for culturally because they propagate from parents to children. Parents who believe that children are a blessing have more children and pass on that belief to them.

Finally, the idea that wealth causes decreased fertility is not consistent with the evidence of history. There are many historical examples of improved living standards causing an increase in human fertility, not a decrease. For example, the Irish population grew rapidly after the introduction of potatoes. French and English settlers in the Americas adapted to conditions of abundance by increasing their fertility. Women married younger and had more children, and the population of Europeans in the Americas expanded rapidly. Until fairly recently, families with 10 or more children were common in Quebec. Even though there was a general decline in fertility across the developed world in the 20th century, fertility rates fell faster and went lower in communist Russia than they did in in the much wealthier United States.

So, there is no reason to believe that increased wealth causes decreased fertility in human beings, although in recent times there has been a correlation between them. The recent correlation between increased wealth and decreased fertility must be due to something else. A more plausible explanation is that low fertility increases wealth. Having fewer children per family means that more energy can be invested in creating capital.

Low fertility might have played a role in the Industrial Revolution in Europe. Western Europeans had lower fertility than most other people around the world, due to the Western European marriage pattern. In Western Europe, women would often delay marriage and children until their mid twenties. The result was lower fertility, and more energy to invest in the creation of capital. Capital increases the efficiency of labor, which allows for more investment in capital, but only if the population does not expand to consume the additional production. The Industrial Revolution was one of the few times in human history when economic growth outpaced population growth, leading to prosperity.

(You can think of the IR as having two phases. The first phase was characterized by increased production, the second phase is characterized by decreased reproduction.)

The recent Chinese economic boom might also be partly due to lower fertility. There was a large decline in the Chinese fertility rate after the communist revolution. Roughly a generation later, the Chinese had a huge economic boom due to industrialization. This boom is usually explained solely in terms of a shift to a more open market economy. I believe that the shift to an open market is only part of the explanation for China’s rapid industrialization and economic growth. I think it was also partly due to low fertility, which shifted energy and labor from the creation of human beings to the creation of capital.

Thus, the generally accepted explanation for the observed modern decline in fertility is incorrect. It is based on a flawed conception of human nature.

What is the true explanation for the modern decline in fertility? The answer is birth control. Birth control decouples sex from reproduction. Our emotions evolved in a world without birth control, a world in which lust caused us to have sex, and having sex caused us to reproduce. Birth control, by allowing people to have sex without making babies, is the major cause of the modern decline in fertility. Cultural and social changes also play a role, especially the breakdown of traditions, including traditional religion, traditional ways of life, and traditional sex roles. Birth control technology, combined with cultural and social changes, caused the sexual revolution: the recent change in human reproductive behavior that followed the industrial revolution.

Why do people believe in DTT? One reason is that it plays an important role in the humanist worldview. To humanists, DTT is part of a “don’t worry, be happy” view of human nature and reality. They believe that low fertility is a sign of progress and enlightenment. They believe that people will naturally choose to have fewer children if they are liberated from economic, cultural and social constraints. In the humanist worldview, low fertility has two benefits. One is that it frees the individual to “self-actualize” (whatever that means). Somewhat ironically, humanists view parenthood as a burden to be liberated from. The other benefit of low fertility, in the humanist worldview, is that it eliminates the problem of population growth, and the resulting conflict over scarce resources. This is important for humanists, because they want to believe that human nature is essentially good and rational, and thus human nature should produce good and rational outcomes if it is liberated from constraints.

Humanists also believe that their worldview and the modern western way of life are the “end of history”. They believe that we are naturally progressing toward that end, and that conservatives are just standing in the way, blocking progress toward a humanist Utopia. They assume that everyone will eventually adopt their worldview because it is good and rational, and because human nature is essentially good and rational. Humanists are wrong about this. Human beings are not good and rational, and humanism is not the end of history. It is a historical dead end.

Now that I have described DTT and its importance to the humanist worldview, I will explain why it is wrong. I have already explained some of the problems with it. Now I will explain why the predicted demographic transition will not happen. To put it simply, DTT is wrong because it ignores evolution.

Human beings are not magic. We are life forms, and evolution applies to us as it applies to all living beings. Modern civilization does not transcend evolution.

Generally speaking, the birth rate that maximizes surviving offspring is selected for. In an environment of abundant energy, in which most children live to adulthood, high fertility is selected for, and low fertility is selected against. Thus, even if many people adopt a low fertility way of life in the modern world, by doing so they select against their genes and their memes.  Conversely, those who adopt a high fertility way of life in the modern environment are selecting for their genes and memes. (Or at least the memes that pass from parents to children as traditions.) Any trait, biological or cultural, that is passed from parents to children and leads to high fertility will increase in the population.

Traits that cause low fertility, on the other hand, do not propagate very well from parents to children. Traits that cause low fertility can propagate laterally by persuasion, as fashions. Right now, fertility rates are still declining in most parts of the world. Low fertility is propagating as part of a cultural package. Most people find the modern, low fertility lifestyle compelling. Low fertility seems to be replacing high fertility. However, this is a temporary effect, not a transition to a new, stable way of life.

A meme that causes low fertility acts like a disease. It selects for traits that make people resistant to it. In the long run, it cannot compete with high fertility. The people who adopt this new way of life leave behind few descendants. On the other hand, those who do not adopt the modern, low fertility lifestyle leave behind more descendants. In the modern environment any genetic or cultural trait that causes high fertility is selected for. That may include traits that we think of as dysgenic, such as low IQ or psychopathy. They will be selected for if they cause higher fertility.

In the long run, the human population will evolve resistance to the meme of low fertility, just as we evolved resistance to other diseases. This will occur by biological or cultural evolution, or both. Low fertility is not evolutionarily stable, and thus it will not persist. Even if we go through a demographic transition, it will not be a permanent condition, but rather a temporary effect of modernity. Like any new disease, it will sweep through the population, infect susceptible individuals, and leave behind a population that is resistant to it. Higher fertility will evolve, either culturally or biologically. More fertile people will replace less fertile people. More fertile traits will replace less fertile ones.

For example, Islam is expanding rapidly due to population growth. That is because Muslims, and especially fundamentalist Muslims, have higher average fertility. They keep women in the home making babies. The Muslim world has grown more fundamentalist in the last 50 years, mainly because fundamentalists had more children than secularists and moderates in Muslim societies. Islam is now spreading to the West, due to population pressure. Muslims are replacing the declining native population of Europe, which has very low fertility.

There are other examples of religions that promote fertility. Take the Amish for example. Their current rate of population growth corresponds to doubling every 20 years. That is almost entirely due to reproduction — there is very little conversion into the Amish community. At their current rate of growth, the Amish population would exceed the current world population in less than 300 years, starting from its current size of 250,000. If everyone else went through the demographic transition except the Amish, then after 300 years the global population would be almost entirely Amish.

In spite of being anti-modern, the Muslims and the Amish are adapted to modernity. They reproduce their genes and their memes. As time goes on, other adaptations will emerge. One thing is certain: humanity will not settle into a stable pattern of low fertility unless we impose it on ourselves.

Demographic transition theory is wrong because it ignores evolution. It assumes that there is a single, fixed human nature, that human nature is universal and constant. That assumption is false. There are variations within human nature, not a single, universal human nature. Human nature is not fixed. It evolves. Human nature was shaped by evolution to make people reproduce. Human nature will continue to be selected for reproductive fitness. We cannot transcend evolution.

There is only one way to have persistent low fertility, and that is for society to impose it on individuals. In the long run, population growth is a tragedy of the commons. Social regulation of individual behavior, imposed by coercion, is the only way to solve a tragedy of the commons. If we want to maintain the modern condition of prosperity in which most children live to adulthood, then we have to socially regulate reproduction. By imposing eugenic reproduction control, we could maintain a stable population and a stable or improving genome. Otherwise, population growth and dysgenics are guaranteed to bring about the collapse of modern civilization. If that happens, we will return to the Malthusian condition in which the human population is limited by premature death.

Those are the only possible destinies for humanity. We can still collectively choose one or the other, but time is running out.


Demographic Transition Theory

Global Fertility Statistics

Western European Marriage Pattern

Muslim Population Growth

Amish Fertility

Amish Population Growth


  1. 1. Historically high wealth was indeed positively correlated with fertility, but without capitalism/female emancipation, wealth plays a very different role. The Marxist view here is probably the right approach.

    2. Children investing in parents: definitely plausible from a selfish perspective. In pre-literate societies, technological/cultural/geographic/etc knowledge is concentrated in old people. Knowledge takes a long time to transmit. Tons of case studies in the anthropology literature. Nestor in the Iliad!

    3. Birth control: mormons have access to it, orthodox jews have access to it, etc. Its existence is important, but you have to have a population willing to use it. Can't be the cause; the will not to have kids comes first.

    That said, obviously you're right about the long run...this is unsustainable. There's still differential fertility, so selection is doing its thing and we're eventually gonna start hitting Malthusian limits again. But the AIs will have eaten us by then, so who cares.


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