Population collapse

This content was translated using artificial intelligence and may therefore contain errors.

The imperatives of biology

As I briefly mentioned in chapter 1, a very particular phenomenon is affecting numerous countries around the world at the same time. Humanity faces an unprecedented crisis: population collapses driven by population aging and falling birth rates. This has never happened anywhere before, so no one really understands what is going to happen, how to reverse it, or how far-reaching its consequences might be. With that in mind, a few questions are worth asking. How did we get here? What processes have guided human reproduction until now? And finally, what can we expect in the foreseeable future?

Let us take a very quick but necessary look back to illustrate the point: for the first few hundred thousand years of our existence, when the survival of our species depended on our skills as hunter-gatherers, the world's population grew at an extremely slow rate. But around 10,000 years ago, a discovery changed everything forever: agriculture. The species Homo sapiens discovered that it could produce food; food in abundance. And as it produced food, it could produce more people, which in turn forced it to produce more food, making it possible to produce more people and more food. And before we knew it, we had cities, walls, ships, armies, laws, trade, and all the other elements that define a human society as we understand it. Ten millennia may seem like a long time, but if we consider that modern Homo sapiens has inhabited Earth for 250,000 years, all of this happened in the blink of an eye.

Settled life brought a new set of challenges. More complex societies gave rise to a division of labor and increasingly specialized jobs. This, in turn, led to social stratification and an unequal distribution of resources. Agriculture provided larger populations with a more abundant food supply, but not necessarily a healthier one. The emergence of urban centers enabled qualitative leaps in cultural, scientific, religious, and organizational development, but these cities without modern sanitation systems posed a major threat to public health, while their higher population density made them particularly vulnerable to the scourge of epidemics.

If we add to this the vulnerabilities inherent in premodern agriculture, the absence of vaccines, antibiotics, or operating rooms, and a moral universe substantially more comfortable with violence than is customary in the 21st century, we end up, as recently as a hundred years ago, with a situation in which life expectancy hovered around 30. This does not mean that someone in their thirties was considered elderly, but rather that the chances of reaching old age were very low, above all because of one factor that dragged average life expectancy down considerably: high infant mortality.

To put this in perspective, in today's world the replacement fertility rate (that is, the number of children who must be born to keep the population at a constant level) is around 2.1 children per woman. Let us contrast this figure with the estimated replacement fertility rate for the Roman Empire: almost 6 children per woman.

In fact, infant mortality was so high in premodern times that people had as many babies as they could to ensure that some of those children actually reached adulthood. This, in turn, made economic sense in a predominantly rural, preindustrial world where the family unit was the main means of production. This concept was so self-evident that it has even survived encoded in the very word economy, derived from oikos, the Greek word for “house.”

And this is where the organizational models of every society around the world came up against the imperatives of biology. The species Homo sapiens produces few offspring, and each takes a long time to mature, particularly in terms of cognitive development. Although our intelligence is undoubtedly the trait that most distinguishes us in the animal kingdom, this virtue did not come without trade-offs: because our brains are large, our heads are large too. We walk upright on two legs, but our hips are narrow. And if we add to this the fact that a newborn baby is quite large relative to its mother's body, we arrive at a preindustrial picture in which complications during childbirth were many; medical solutions, few; and deaths among both offspring and mothers, frequent.

These dangers naturally do not affect men—at least not individually—for whom the biological risks of reproduction are much lower. At the same time, a man's reproductive capacity is immensely greater than a woman's. Generally speaking, it is highly unlikely that a woman could have much more than a dozen children in her lifetime, while a man is capable of producing hundreds. This brings us to the counterintuitive but scientifically established fact that people have more distinct female ancestors than male ancestors. This is because more women became mothers than men became fathers, but a few men had an extraordinary number of descendants. In other words, if a man had 100 sons and daughters with different women (and there are recorded cases that far exceed this number), and each of them gave him 10 grandchildren, and each of those grandchildren gave him 10 great-grandchildren, that first man would have produced 11,100 direct descendants in just three generations. And within that mass of people, it is statistically likely that some of his descendants' descendants will end up reproducing with one another. This creates a sort of “genetic bottlenecks.”

A striking example of this was illustrated in a study published in the journal Nature in 2003. Drawing on a substantial genetic sample from across a large region of Central Asia, the study concluded with a high degree of certainty that 8 % of the samples across 16 ethnic groups (including the Han Chinese, the world's largest ethnic group) shared a common ancestor from Mongolia, who was in all likelihood the great conqueror Genghis Khan. But despite exceptional cases like Genghis Khan's, the lives of the vast majority of humanity were marked by the tragic reality of reproducing as much as possible in the hope that a handful of all those children would reach adulthood.

In short, the global picture was one of short and brutal lives, with extremely gradual population growth.

Monogamy, polygamy, hypergamy

Cultural parameters with some lasting effects were gradually added to this biological reality shared by the entire species. Although there is a broad spectrum of ways in which human societies have organized reproduction, three particular phenomena deserve attention: monogamy,  polygamy and hypergamy.

The last of these concepts, hypergamy, refers to a common practice observed in cultures around the world and throughout history in which individuals form partnerships with people of the same status or higher, generally according to socioeconomic criteria. This practice was commonly pursued by women and/or their families in response to the limited economic opportunities women faced in a preindustrial world.

As for polygamy, this arrangement has notably harmful effects on a society's internal stability. Since, generally speaking, the numbers of men and women tend to be roughly equal in most cases, polygamy, when it becomes common practice, quickly creates a shortage in the sexual marketplace. Under this arrangement, men with multiple women will be older men of higher status, while those disadvantaged by this policy will mostly be younger men of low status. This becomes particularly significant when we consider that low-status men between the ages of 18 and 25 are, statistically, the most violent demographic group. Throughout history, these men with nothing to lose (and everything to gain if they were willing to risk their lives) have been the raw material that filled the ranks of soldiers, mercenaries, sailors, pirates, guards, smugglers, police officers, gang members, and revolutionaries. Consequently, the presence of vast numbers of armed and frustrated young men has traditionally been a recipe for brutal social upheaval.

As for monogamy, some theories hold that it was a significant factor in the development of various cultures, notably European culture. Because, again, societies tend to have roughly equal numbers of men and women, monogamy leads to the vast majority of people ending up in a couple, which largely defuses the social pressures that hypergamous practices can generate. At the same time, in the premodern world, people married relatively young.²⁴It is important to note here that the concept of adolescence only developed in the late 19th century, and that the transition from childhood to adulthood was therefore more abrupt, with no intermediate stages. In this way, people paired up and reproduced early in life. And this helped create a degree of stability in a world in which, before the Industrial Revolution, around 85 % of people lived in extreme poverty but had children and, therefore, something to lose.

And suddenly, a hurricane swept across the world, changing it forever. That hurricane is called industrial modernity. Its transformations allowed societies to support far more people, and as a result, the global population soon exploded: in 1800, it stood at around 1 billion people. Within 127 years, it had doubled. Less than fifty years after that, it had doubled again. And fifty years later, it had doubled a third time. And that is how, thanks to the Industrial Revolution, we went from 1 billion to 8 billion people in just two centuries.

The decline

Yet the very same features that made this population explosion possible are now poised to trigger a population collapse. Falling fertility is an extremely complex phenomenon resulting from the convergence of numerous independent factors. According to the United Nations' World Population Prospects, between 1950 and 2023 the global fertility rate fell from around 5 children per woman to 2.3 children per woman, placing it just above the replacement fertility rate, and it is expected to keep falling. If we had to identify the main culprit, it would be industrial modernity: this new civilization we have developed over the past two centuries. But putting it that way is not enough, so in the following pages I will give a detailed account of all the ways in which today's society has led people to reproduce less and less.

Urbanization and individualism

With the Industrial Revolution, the center of the economy moved to the city, while most people began to do the same. The logic of manufacturing production accompanied the exponential growth of urban centers, where more and more people began living increasingly anonymous, individual, and lonely lives. In this way, the concept of individualism, understood as the moral and philosophical position that emphasizes the central value of the individual and personal fulfillment, became increasingly dominant in the common sense of the contemporary world.

Costs

Urban industrial advances also led to the introduction of technology into agricultural production, reducing its need for labor and accelerating migration from the countryside to the city.²⁵The year 2007 is remembered for a number of events, but it saw one generally overlooked development that represents one of the most consequential milestones in our history: it marked the first time the urban population outnumbered the rural population.

In this new urban environment, children went from being an economic asset to an expense and, in some cases, a luxury. At the same time, dramatic declines in infant mortality dismantled the earlier Darwinian imperative to have many children. The development of the idea of adolescence, along with greater access to formal education and its longer duration, extended individuals' already lengthy period of maturation and, with it, increased the cost of raising children. This lengthening of people's formative years also significantly delayed the average age at which they began having children and further contributed to fewer births.

Employment opportunities

The emergence of wage labor, accompanied by the expansion of manufacturing and the development of the service sector, created new employment opportunities for both men and women, with women entering the workforce outside the home in ever greater numbers. This increased the supply of labor and therefore lowered its cost. As a result, in many occupations a single income was no longer enough to support a family, and two wage incomes per family gradually became a necessity in large urban areas.

At the same time, women's entry into formal employment did not generally mean a significant reduction in their family caregiving responsibilities. Although there have been cultural and legislative changes in some cases (from a more equitable division of household tasks to maternity and paternity leave), human reproduction ultimately continues to depend on an undeniably unequal burden on women.

The crisis of institutions

The rapid development of science and technology brought about a crisis in long-standing religious beliefs and their traditional moral frameworks, firmly anchored in the pronatalist values of a predominantly rural world. In their place, different constellations of thought emerged, ranging from militant forms of atheism to respectfully indifferent forms of agnosticism, along with assorted grab bags that mix elements from different ethical codes without any clear organizing principle.   

The exponential increase in humanity's general prosperity, the codification of labor law, and the development of modern social security systems gave individuals a previously unthinkable degree of autonomy and diminished the once-crucial importance of the family structure. Likewise, the legalization of divorce and the gradual easing of access to it also transformed the very meaning of marriage, which went from being a lifelong commitment to an arrangement subject to individual choice.

Voluntary termination of pregnancy

Technological advances also improved methods of terminating pregnancy, which gained increasing legal recognition around the world. Although the history of abortion is long and complex,²⁶The earliest mention of abortion we have is found in the Ebers Papyrus, an Egyptian document from 1500 BC, while the earliest mention of the criminalization of abortion appears in the Assyrian legal code from 1075 BC. many techniques for terminating pregnancy in the preindustrial era were accepted practices, explicitly or implicitly, in numerous cultures. In many cases, the established criterion was that an abortion could only be performed before the fetus had begun moving inside the womb, which happens on average between weeks 18 and 20. This, in turn, was tied to the belief that this was the moment when the soul entered the fetus. 

There have been numerous advances and setbacks on this issue around the world over the years, but throughout the 20th century and this first quarter of the 21st century, a general trend toward broader legalization can be observed. On the one hand, scientific advances in improving both surgical abortion methods (such as vacuum aspiration or dilation and evacuation) and medication abortion methods (such as misoprostol and mifepristone) made abortion more accessible and reduced its risks. On the other hand, the growing influence of sociocultural movements such as second-wave feminism in the 1960s and 1970s, which counted reproductive rights among its main causes, brought this debate onto the public agenda on a larger scale.

According to the Center for Reproductive Rights, around 662 million women of reproductive age (34 %) currently live in the 77 countries that allow abortion on request. Added to this figure are the nearly 1.1 billion women of reproductive age who live in the 103 countries where abortion is legal on socioeconomic grounds, on health grounds, to save the woman's life, and in cases of pregnancies resulting from rape and/or incest. By contrast, around 111 million women of reproductive age live in the 21 countries that prohibit abortion entirely.

According to studies published by the Guttmacher Institute using available data from the United Nations Statistics Division and the United Nations Sustainable Development Goals, between 2015 and 2019 there were an average of 252 million pregnancies per year worldwide, half of which were unintended. Of all pregnancies, an estimated average of around 29 % ended in abortion, while that figure rises to 60 % for unintended pregnancies. This represents an average of 73 million abortions per year.

For a variety of reasons, unintended pregnancy rates tend to be higher in countries that restrict access to abortion and lower in countries where abortion is broadly legal. As a result, abortion rates end up being similar across both groups of countries. Although the global unintended pregnancy rate has declined since 1990, the global abortion rate has remained stable. This has led to an increase in the proportion of unintended pregnancies ending in abortion, from around 50 % in 1990 to around 60 % in 2019.

To assess these global figures, we must also consider the impact of various government policies implemented around the world with the explicit aim of reducing fertility, policies that vary greatly in scope, effectiveness, and degree of coercion: from sex education programs in secondary schools to reduce teenage pregnancy to national campaigns such as the one-child policy in the People's Republic of China, the forced sterilizations carried out by Prime Minister Indira Gandhi in India, or those carried out by President Alberto Fujimori in Peru.

Another factor is the increased effectiveness of and broader access to modern contraceptive methods, especially the birth control pill. This allowed humanity, as never before, to separate sexual activity from its potential consequence: reproduction.

Sexual revolution

These new material conditions soon made their way into the cultural sphere, which underwent a sexual revolution that weakened and redefined earlier taboos. One of the most notable transformations in this regard has been the growing visibility, legal recognition, and acceptance of the LBGT community over the past fifty years. As a result, millions of individuals in more and more countries around the world, who at another time would have been pressured and/or forced to form families with people of the opposite sex, have been able to openly embrace their sexual identity and lead lives that in previous centuries would have meant social condemnation, ostracism, or legal persecution.

The other major effect of the sexual revolution has been a change in how romantic relationships themselves are understood. The decline of monogamy's previously hegemonic status (which, for centuries, had been virtually unquestioned in the West) gave rise to a culture more open to different forms of relationships. This led to the growing popularity of sexual and romantic relationships that are generally more fleeting and less committed than the old marriage formula of “till death do us part,” and to a sustained rise in singlehood. This, in turn, has produced a phenomenon that could be described as a kind of “sexual free market,” in which the laws of supply and demand have progressively taken hold. In a context where fewer lifelong partnerships are formed and singlehood consequently increases, we can see how intense competition has been unleashed, with dynamics that ultimately produce unequal outcomes across society. This is where we must return to the subject of hypergamy.

Incels

As already mentioned, hypergamy is a practice more commonly pursued by women or their families, who tend to seek partnerships with men of the same or higher social status, a broad category that can be expressed through various indicators, such as educational attainment or income. According to several studies, this is accompanied by the fact that women generally have more complex selection criteria than men and tend to prioritize quality over quantity in their search for partners. 

In a context where commitment in relationships becomes less solid and competition to find a partner consequently expands, the main consequence of this dynamic is that the vast majority of women end up competing for the same small segment of men, who face more demand than they can handle. This level of competition makes it very difficult for many women to find a steady partner within the segment of the population they are targeting. Meanwhile, a vast majority of men face considerable difficulties in forming any kind of partnership. In fact, two of the groups that tend to face the greatest obstacles in finding a partner are low-status men and high-status women. 

Among the methods of textual criticism used by historians, there is a principle known as the criterion of multiple independent sources. In short, this criterion holds that when two or more dissimilar and independent sources reach the same conclusions, the likelihood that those conclusions are correct increases. A striking example of this principle clearly at work can be found in relation to the situation described above.

On the one hand, the concept of hypergamy features prominently in various internet subcultures with misogynistic tendencies, such as the “red pill” and incels. As for the “red pill,” this is an internet subculture whose name is inspired by the famous scene in the film The Matrix in which the protagonist, Neo, faces the choice of taking a blue pill and continuing to live in the artificial world imposed on him, or taking the red pill and beginning to live in the real world. Drawing on that analogy, this online community maintains that a man “takes the red pill” when he awakens to the reality that the contemporary world is designed to work against the interests and well-being of most men, particularly young men. This online community also overlaps considerably with the incel internet subculture, whose name is an abbreviation of the term involuntary celibate (“involuntarily celibate”). This identity, which has emerged through social media in recent years, is overwhelmingly composed of young men who routinely express frustration and resentment about their inability to have sex. Generally, the causes that incels themselves identify as underlying their predicament lie both in their own “undesirable” qualities and in structural social practices and women's sexual practices, usually described as Machiavellian, utilitarian, and calculating. Indeed, leading figures in these spaces, such as the influencer Andrew Tate or the psychoanalyst Jordan Peterson, repeatedly mention the term hypergamy in their analyses. Both Tate and Peterson use this concept in their critiques of postmodern society to justify their own far-right agendas.

In a qualitatively different part of the political and ideological spectrum, we find a very different source that, without using the same terms, describes precisely the problem of hypergamy, stripped of the misogynistic content of the “red pill”: the opening monologue of the first episode of the first season of the television series Sex and the City. The iconic late-1990s series follows the adventures of writer Carrie Bradshaw and her three friends, a group of attractive, sophisticated, professionally successful women navigating the vicissitudes of singlehood together in their thirties in New York City. The series begins with a monologue in which Carrie ponders the fate of Elizabeth, a beautiful English journalist who, after a passionate romance with a successful banker, is suddenly abandoned without explanation. Faced with this phenomenon, Carrie poses the following question: 

This question is followed by a montage in which various characters offer their own theories. Peter Mason, a man described as an advertising executive and a “toxic bachelor,” declares: “When you're a young guy of 20, women control relationships. When you're a desirable man of 30, you feel like women are devouring you. Suddenly, men hold all the cards. I call it ‘the thirtysomething power shift.’” He adds that “there isn't a single woman in New York who hasn't rejected ten wonderful guys because they were too short, too fat, or too poor.” For her part, Charlotte York, an art dealer and one of the show's main characters, states, on the one hand, that “most men feel threatened by successful women” and, on the other, that “as we get older, we're choosing from smaller and smaller pools [of men].”

 These examples, produced by people with radically different views of society, are symptomatic of a curious phenomenon that can be observed in many modern societies, particularly in the West. In a sense, the dynamics of today's dating market have ended up reproducing polygamy, creating a situation in which forming stable partnerships becomes progressively more difficult. 

According to a Pew Research Center study, in 2022, 30 % of American adults were neither married, living with a partner, nor in a committed relationship. This trend was even more pronounced among younger generations, with around half of young adults being single. However, this phenomenon was not evenly distributed between the sexes: while 34 % of young women were single, the figure reached 63 % for young men. 

Meanwhile, according to an investigation by the Washington Post, over the three decades from 1989 to 2018, the percentage of people between the ages of 18 and 30 in the U.S. who reported not having had sex in the previous twelve months rose from 14 % to 23 %. It is worth noting, however, that this figure doubled for men (from 15 % to 30 %), while women saw a less significant increase (from 12 % to 18 %). It should also be noted that, according to an Indiana University study, men with lower incomes, those working part-time, the unemployed, and students are the most likely to be sexually inactive.

This trend is compounded by another phenomenon we can observe throughout the industrialized world: a significant increase in lives lived alone. One interesting example is Japan, a country characterized by a notably collectivist culture, where single-person households have been steadily increasing for several decades. The impact of this change has been such that it has led to the emergence of ohitorisama culture. This term, which could be loosely translated as “for one person,” refers to a new movement led by generations of young adults seeking enjoyment and personal fulfillment through solo activities—a remarkable cultural transformation in a society that has always placed enormous emphasis on a sense of group belonging.

To this we must also add the negative impact of social media, particularly among younger generations. The so-called centennials or Generation Z are the generation born from the second half of the 1990s (the exact year varies depending on the criteria and the country) to approximately 2010, when the next generation, known as Alpha, begins. The historical experience that has defined this generation is having been subjected to two major historical changes simultaneously. On the one hand, they were, almost universally, the most overprotected generation in history. This significantly limited their exposure to key developmental experiences throughout childhood and adulthood, negatively affecting their maturation. On the other hand, from around 2010 onward, centennials have been the first generation raised with smartphones and social media, exposing them, without any protection whatsoever, to significantly harmful, highly addictive, and poorly understood new technologies. The result has been a mental health crisis that has affected centennials almost simultaneously around the world.

This combination of factors has led to various cultural responses marked by a clear spirit of resignation, such as China's “lying flat” movement, in which young people reject the hypercompetitive demands of the professional labor market and, as a method of resistance, urge members not to marry, have children, or consume. A more extreme case can be found in a phenomenon originating in Japan but increasingly present worldwide: the hikikomori, a kind of urban hermit who shuts themselves away in their home or bedroom, thereby limiting contact with the rest of humanity, including their closest family members.

This tendency toward withdrawal among young people is facilitated by a growing supply of substitutes for human intimacy made possible by technological development. On the one hand, compulsive pornography use, particularly among young men, has been shown to correlate both with greater subsequent dissatisfaction with interpersonal experiences and with greater reluctance to seek a partner. On the other hand, artificial substitutes for partners are becoming increasingly popular, from progressively more realistic and sophisticated sex dolls, to the meteoric rise of sexual and romantic relationships formed with artificial intelligence programs. This phenomenon is not a substitute practice solely for single and/or lonely people; cases can also be found among people in stable relationships with other human beings, as illustrated by an article in People magazine recounting the case of a woman who, after falling in love with a customized version of ChatGPT, ended up divorcing her husband.

Progressive women, conservative men

These transformations in individuals' lifestyles are also accompanied by correlations in the political sphere. In recent years, a growing ideological divergence between men and women of the same generations has been observed around the world. Broadly speaking, the trend shows increasing numbers of women adopting increasingly progressive positions and increasing numbers of men adopting increasingly conservative positions. 

Moreover, this growing ideological divergence between men and women is occurring within the same generations, especially younger ones. A Gallup survey indicates that between 2018 and 2024, a split emerged in the U.S. between men and women aged 18 to 30, leaving women 30 percentage points more progressive than their male peers. In Germany, too, there is a 30-point gap between increasingly conservative young men and increasingly progressive young women, while in the United Kingdom the gap is 25 points. In many places, this situation has also translated into clear party allegiances, as in Poland, where, in 2023, almost half of men aged 18 to 21 supported the far-right Confederation party, while support among women of the same age was just 17 %. In South Korea's 2022 presidential election, young men strongly supported the right-wing People Power Party, while young women backed the liberal Democratic Party in almost equal numbers. This is particularly interesting because, in that same election, there was no difference in how older men and women voted.

In South Korea, this political trend has also manifested itself in social life and gender relations. The most emblematic case is the 4B Movement, a radical current within the South Korean feminist movement. Its name originates in a play on words, since “bi” is a negative prefix and refers to the “four noes” that the movement upholds as its fundamental pillars: no marriage to men, no having children with men, no romantic relationships with men, and no sexual relationships with men. The movement also gained significant worldwide visibility after going viral on American social media following Donald Trump's second presidential victory in November 2024, an election in which the rhetoric of political debate was also shaped by gender relations.

Fecundity and fertility

Alongside this multiplicity of converging sociocultural factors, a growing biological problem has also been observed: increasing deficiencies in human beings' biological capacity to reproduce. 

Here we must pause to address a confusing but important terminological issue: the difference between fertility and fecundity. Within the discipline of demography, fecundity refers to the biological capacity of human beings to reproduce sexually, while fertility refers to the actual number of children ultimately produced. However, the distinction between these terms is not always consistent across different disciplines or in their application, which often creates some degree of confusion. In light of this, I will consistently use the definitions given earlier in this paragraph.

As for male fecundity, a series of recent studies indicate an increase across the entire spectrum of male reproductive problems, including declining sperm counts, declining testosterone levels, and rising rates of erectile dysfunction and testicular cancer. A global study published in 2022 also indicated that sperm counts fell by an average of 1.2 % per year between 1973 and 2018: from 104 to 49 million/ml. Far from slowing or leveling off, the study indicated that this trend accelerated to more than 2.6 % per year from 2000 onward, while infecundity already affects around 7 % of the male population. Added to this is the fact that, simultaneously, the incidence of testicular cancer has increased exponentially. These problems are not only statistically significant but also remarkably widespread across the planet, with cases recorded in places as disparate as South America, China, Africa, northern Europe, North America, and Australasia.

While certain individual habits can negatively affect fertility (such as a poor diet, a sedentary lifestyle, stress, and alcohol and drug use), other research has shown the harm to fecundity caused by chemicals found in plastics, medicines, food, and the air. These environmental toxins also have some specific effects on women, as they can trigger problems such as polycystic ovary syndrome, primary ovarian insufficiency, and meiotic defects, such as aneuploidies. However, beyond the concrete problems affecting individuals today, there is also concern about the heritability of these conditions. It has been confirmed that some substances can cause oxidative damage to male and female DNA and are recognized mutagens capable of inducing multigenerational infertility in animals. This strongly suggests that such substances could leave lasting, multigenerational consequences through a combination of genetic and epigenetic effects.

We must also consider the unexpected impact of introducing technology specifically designed to address problems with procreation, such as assisted reproductive techniques. While these technologies can, in the short term, help people who could not otherwise reproduce to have children, in the long term this could pose a problem, since those children could inherit the same difficulties. One notable example is mutations associated with azoospermia that are inherited directly from father to son. A particularly clear case involves certain Y-chromosome microdeletions: when a man carrying one manages to have a child through assisted reproduction, his sons inherit the same genetic alteration and may, in turn, experience fertility problems. In some countries, such as Australia and Denmark, 1 in every 16 children is already conceived through assisted reproductive techniques, and the growth of this trend appears inexorable. The great irony of the assisted reproduction industry is that it may be helping to propagate the very pathology it seeks to treat, since the more assisted reproduction is used in one generation, the more necessary its use will become in the next.

Old age, immigration, and politics

Although we have so far detailed the multiplicity of causes that have led to declining fertility around the world, we must mention another equally relevant and intimately related correlate: population aging.

In recent decades, advances in medicine have significantly extended people's life expectancy, leading to a notable increase in the number of older people in most countries around the world. This phenomenon compounds all the other converging factors detailed above and has resulted in a situation in which, broadly speaking, the longer people live, the further the birth rate falls.

Consider that young people (say, those aged 18 to 65, just to put a number on it) support, directly and indirectly through their work, those who do not work, essentially children and the elderly. This means that the more elderly people there are, the less money young people will have to have children. This leads to a situation in which there will be more elderly people, fewer young people, and fewer children. Which, in turn, results in more elderly people, fewer young people, and fewer children. At the same time, growing pressure on the economically active population creates greater incentives to emigrate to countries with better wages, accelerating the problem and leading to an increasingly inverted population pyramid.

Advances in medicine have generally not been accompanied by changes to pension legislation. Pension systems in most countries that have them are based on models developed after the Second World War, during the emergence of the welfare state. The average retirement age generally ranges from 60 to 65. The logic behind this was based on life expectancy being around 70, meaning that people would typically have about a decade of retirement before dying. Today, life expectancy in the most advanced countries is approaching 85, and it has become relatively common for individuals to reach the age of 95.

Although there is growing debate about raising the retirement age, such proposals tend to face strong opposition and do not offer structural solutions. First, raising the retirement age makes young people's already difficult entry into the labor market even harder, creating other sources of instability. Second, this is unlikely to be enough to make the pension system sustainable. Finally, raising the retirement age does not change the composition of the population pyramid, which is the main source of the problem.

In turn, if we bear in mind that pension systems are based on the calculation that approximately three workers are needed for every retiree, this means that 9 workers will then be needed for those 3 retirees; 27 for those 9; 81 for those 27; 243 for those 81; 729 for those 243; and 2187 for those 729. To put it more bluntly, the pension system is a pyramid scheme based on the assumption of constant, uninterrupted population growth. Added to this is the fact that in many countries around the world, baby boomers (those born between 1945 and 1960, depending on the calculation used) represent the largest generation in human history, especially in the most advanced economies. By the end of the 2020s, almost all baby boomers will have retired, and each successive generation is already smaller.

In these scenarios, immigration is often cited as the logical and obvious solution to population aging and declining birth rates. While it is true that, in the short term, immigration can mitigate some of the effects of this phenomenon, several additional factors must be taken into account. First, nothing guarantees that immigrants arriving in a country will arrive at the times, in the numbers, and with the specific training that the particular conditions of a national economy require at any given moment. Second, there is a clear and recurring correlation between population aging, declining birth rates, and rising anti-immigrant sentiment among the native population. An example of this can be seen in the growth of xenophobic rhetoric and far-right parties across Europe and North America in recent years. Third, mass migration also brings a set of social problems and cultural transformations that are particularly challenging for the modern nation-state model. In this regard, cases such as Argentina offer notable and exceptionally successful examples of building multicultural societies.

Finally, demographic problems are particularly difficult to resolve through national policy because incentives are misaligned. The problem is that the 2020s are probably not the time to make drastic decisions to tackle this issue; that time may well have been the 2000s. Now, who would be willing to make political decisions likely to be unpopular that require them to pay a significant and immediate price in an attempt to prevent a scenario that could become a serious problem in thirty to forty years? The answer is virtually no one.

In turn, as birth rates fall and the population ages, older people make up an increasingly large share of the population and the electorate. In countries where voting is optional (most democracies), they tend to exercise this civic right more often than younger people. This means that, in many places, older people are already a decisive factor in every election, making it progressively more difficult to implement public policies that would significantly alter pension systems or immigration policies.

Faced with such a critical situation, wouldn't people be able to set aside their reservations and welcome with open arms all the people who want to come to their shores seeking to build a better future? That is certainly possible. The question would be what kinds of people, and how many of them, would be willing to move to a country whose economy was undergoing a sustained collapse.

The death of the baby boomers

While much hope is being placed in advances in automation and artificial intelligence, nothing guarantees that these developments will happen quickly enough or represent qualitative leaps large enough to maintain a functioning economy amid population collapse. Added to this is the fact that using technology to replace tens of millions of workers and increase the productivity of the remaining workers would involve a colossal investment.

On the other hand, there is the argument that productivity increases driven by technological advances could create a significantly more prosperous society even with fewer inhabitants. The problem with this reasoning is that, in current economic models, an essential driver of GDP is consumption, and consumption is largely determined by population size. In fact, the more an individual earns, the smaller the share of their income that tends to go toward spending, while the share that goes toward savings tends to increase.

In turn, baby boomers are also the wealthiest generation in human history. This is particularly relevant because, generally speaking, as people retire, they tend to make fewer investments, especially risky ones, and increasingly live off what they have already accumulated. This means that the availability of capital worldwide could shrink over the next ten years.

There is also much speculation about what the end of the baby boomers will look like and what impact it will have on their children's generation, the millennials (those born roughly between 1985 and 1995). On the one hand, the death of the baby boomers could trigger the largest transfer of resources ever seen in history, transforming the economic reality of millennials through inheritance and resolving many of the challenges and constraints this generation has faced (such as a lack of access to homeownership and high personal debt). However, increasing longevity could lead baby boomers to spend the vast majority of their savings over decades of retirement, leaving little or nothing for their descendants. In this scenario, rather than triggering economic redistribution, current inequality could deepen as large corporate conglomerates controlling sectors such as private health care, pharmaceuticals, and nursing homes enjoy extraordinary profits.

The combination of these factors presents us with a scenario in which nothing guarantees that technology can keep these economies afloat, that there will be enough capital available for the titanic investments required for this grand socioeconomic experiment, or that people will be willing to attempt it as these national economies begin to buckle.

An unprecedented challenge

In light of this, the most likely scenario at present is that, over the coming decades, we will see sustained population collapses in many of the world's most advanced countries. Young people will continue to have fewer and fewer children, many will continue to leave their countries in search of better opportunities, and older people, sooner or later, will die. This will result in a sustained decline in both their populations and their economies.

It is important to stress that, for these countries, these population collapses do not constitute a solution (a painful one, but a solution nonetheless) to the problem, since they would not alter the structure of their population pyramids. After a population collapses to half its size, that same population will continue to face the same problems that triggered the phenomenon: many older people, few young people, and few children, resulting in more older people, fewer young people, and fewer children, while the total population continues in free fall.

It should also be noted that while declining birth rates are a virtually universal phenomenon (the most notable exception being sub-Saharan Africa), the most severe cases are found in North America, Europe, and East Asia, which also happen to be the world's most advanced and important economies. If advances in AI and automation are not developed and deployed quickly enough (an entirely plausible scenario), these economies will essentially have two divergent options.

On the one hand, they can compete with one another to see who can attract the largest number of people to their economy in a global zero-sum migration game. While this might keep their economies afloat, the process would in all likelihood entail an irreversible transformation of these nations' ethnic, cultural, religious, and sociopolitical composition, with inevitable consequences for their levels of internal cohesion. In turn, this could drain the Global South of increasingly scarce human capital, sabotaging its prospects for development in the foreseeable future. On the other hand, the most advanced economies could continue their already visible anti-immigration trends and accept whatever fate has in store for them.

Two particularly notable cases of population aging, declining birth rates, and limited openness to immigration are South Korea and Japan. South Korea has the world's lowest birth rate: 0.7 children per woman. This is particularly delicate because its geopolitical antagonist, the nuclear power North Korea, despite having a smaller population (some 27 million people), does not face a population-aging problem: in a few decades, it will have far more young people and, consequently, far more soldiers. As for Japan, between 2024 and 2025 this archipelagic nation witnessed one million more deaths than births, a trend that will only continue in the years ahead, against the backdrop of the world's most indebted economy and a crisis of political representation that saw the rise of the anti-immigrant far right with Prime Minister Sanae Takaichi's accession to power.

The most likely scenario, however, will be a middle course between closing borders and promoting immigration. Far from remedying the situation, this moderate and/or inconsistent stance could lead to a perfect storm in which countries fail to avert demographic collapse (and the ensuing socioeconomic crisis) but also fail to avoid the challenge of reconciling the contradictions of a suddenly more multicultural and impoverished society under markedly adverse circumstances.

How far will this process go? The clear and frank answer is that no one knows, because this phenomenon is entirely unprecedented in human history, and there is therefore no past experience to use as a reference. The only certainty is that humanity will have to learn to deal with this challenge in real time and on an ongoing basis to confront what could become one of the most consequential crises of the 21st century.

Argentine women and men

As for our Argentine Republic, this outlook presents a complex long-term challenge. On the one hand, Argentina's sustained decline in fertility has become increasingly visible in recent years and, considered in isolation, may be cause for alarm about the country's future. However, when this fact is considered in the global context, a historic opportunity around mid-century comes into view.

First, slower population growth allows economic growth to have a greater impact for a time. If the economy grows faster than the population over the coming decades, this makes it easier for the fruits of that greater future wealth to benefit society as a whole. This is no small matter in a country that has seen rising economic inequality in recent years. Second, while Argentina will inevitably age in the medium term, our country is still in the early stages of this process. According to a 2024 CIA study, Argentina's median age is 33.3 years, placing it slightly above the global average (31.0) and 112th in an oldest-to-youngest ranking of 230 countries and autonomous territories around the world.

Thanks to these trends, we can envision an Argentina that by 2050 is going through a period of population stability and greater prosperity, while many of the world's most advanced economies are in the midst of demographic collapse. In this scenario, our country's comparatively better situation could once again make it a destination that attracts vast numbers of immigrants from around the world, allowing us to stabilize our population in the second half of the 21st century. At this point, the resilience and adaptability demonstrated by Argentine civic nationalism could prove an invaluable resource in a world undergoing profound changes.