When a Species Begins to Ask Why It Reproduces

Why is it that the more humanity develops, the less willing we are to have children?

If we rely solely on personal experience, it is easy to attribute this question to things like "high pressure on young people," "soaring housing prices," or "the high cost of raising a child." But looking at the world at large, this is actually a profound demographic transition unfolding on a massive scale.

According to the UN's World Population Prospects 2024, the global total fertility rate has dropped from 3.31 in 1990 to approximately 2.25 in 2024. Although the global population is still growing, it is projected to peak at around 10.3 billion in the mid-2080s before taking a downward turn. This means humanity is undergoing a long and irreversible cycle: from a population explosion to slowing growth, and ultimately, into contraction.

Different countries currently find themselves at different points along this transition curve. In 2024, Nigeria's fertility rate remains as high as 4.4; India's has dropped to about 2.0, hovering near the replacement level; the US and Canada are at roughly 1.6 and 1.3 respectively; while China has dropped to about 1.0. These numbers do not simply correspond to "rich" and "poor"; rather, they are a reflection of the different developmental stages of these societies.

Due to the demographic momentum generated by massive young populations, population sizes won't immediately stagnate just because fertility rates fall. The populations of India and Nigeria will continue to climb for decades to come. Meanwhile, China's population has already entered a phase of negative growth, with the UN's medium-variant projection suggesting it could fall to roughly 630 million by the end of this century.

Throughout human history, survival has been the overarching theme—our primary challenge was always how to keep more children alive. Disease, famine, and war constantly harvested lives, until modern medicine, clean drinking water, and public health technologies drastically reduced mortality rates, triggering a population surge. Yet today, some societies are facing the exact opposite paradox: now that we finally have the capacity to ensure the vast majority of children grow up safely, why are more and more people choosing to say no?

Perhaps population decline is not merely an economic predicament, but a natural byproduct that inevitably emerges when civilization reaches a certain stage of development.

The Tension Between Intelligence and Reproduction

This cannot be boiled down to a simplistic "smart people don't have kids." In reality, declining fertility is the result of interwoven factors like urbanization, widespread education, gender equality movements, and soaring living costs.

Beneath these surface phenomena, however, lies a deeper fundamental shift: the intelligence humans possess has given us the capacity to transform "reproduction" from an irresistible biological instinct into a calculated life choice.

Animals do not hold family meetings to weigh whether the current economic climate is suitable for raising offspring, nor do they calculate the impact of reproduction on their career development. They simply follow a highly concise underlying code: survive, then reproduce. The complex human brain, however, has added a backdoor-like inquiry to this code: Why?

And once an organism starts asking "why," it is no longer entirely subjugated to its original biological programming.

The movie Idiocracy once explored this issue in a farcical, even vitriolic manner: the smart, educated people in the film become increasingly reluctant to procreate because they are too cautious, while those who don't consider the consequences multiply endlessly. Consequently, centuries later, human society is overrun by "idiots."

This is, of course, not a serious demographic theory, and the real-world relationship between intelligence, education, and fertility cannot be drawn as a simple causal line. But it amplifies a subtle contradiction: when a species possesses the intelligence to decide whether or not to reproduce, that intelligence itself becomes the shackles restraining the reproductive urge.

Attack on Titan pushes this detachment to the extreme. Zeke Yeager proposes the "Euthanization Plan," attempting to strip the Eldians of their reproductive abilities so the race dies out naturally, thereby eradicating all suffering and conflict. It's a terrifying thought: if a highly self-aware species determines that much of the suffering in this world stems from "continuous birth," then "ceasing to be born" suddenly looks like a once-and-for-all cure.

But this immediately gives rise to another philosophical paradox: does a generation have the right to decree to an unborn life that "you shouldn't exist"?

At this point, the discussion transcends demographics and cuts right to the heart of freedom, life, and existence itself. Technology and modern concepts have allowed modern humans to achieve an unprecedented "unbundling": sex is not necessarily tied to love, love doesn't always lead to marriage, and marriage does not inevitably result in reproduction. Contraceptive technology, modern medicine, social security, women's education, and economic independence have made it entirely possible for an independent individual to live completely detached from traditional family structures. This remarkable achievement means that humanity can now largely defy its own biological logic.

So, having shattered the old logic, what kind of new logic have we constructed?

From Animal Society to Modern Society

Sometimes I think that thinking is simply the original sin. Without these heavy thoughts, wouldn't there be a lot less trouble?

But if we actually thrust humanity back into the animal kingdom, how would things play out?

Under those laws, there is no absolute equality in the right to reproduce. Resources and mating opportunities are highly concentrated among a few strong individuals, and the competition is extraordinarily brutal. If modern civilization were to collapse, plunging us back into a jungle society where physical strength, appearance, and pack status dictated everything, many modern humans would actually find themselves heavily disadvantaged.

Take myself as an example. If mate selection relied purely on physical traits, my flaws of being of average height, nearsighted, and having ordinary looks would only be infinitely magnified. It is precisely the modern civilization built upon thinking that has broadened survival competition from pure physical combat into the cultural dimension. An ordinary person can win social status through knowledge, programming, photography, music, or a sense of humor.

You don't necessarily have to be a physically flawless animal to be a valuable human being.

In this sense, civilization has bestowed upon humanity an abundance of "secondary traits" that never originally existed. However, civilization did not eliminate mating competition; it merely made the competition based on these "secondary traits" vastly more complex and diverse. Mating in traditional societies might have revolved around health, resources, family, and social standing, whereas modern society has layered on education, income, values, and even lifestyle.

Ironically, the internet has quantified all of this into the most efficient user interface. In the past, you relied on years of interaction to discover that someone was interesting; today, a few polished photos, a brief career description, and a handful of tags are enough for people to thoughtlessly swipe left or right on dating apps. We created civilization to escape the absolute determinism of biology, only to build a massive marketplace that puts every human trait back on the shelf for comparison.

Modern society appears civilized, but it may just be wrapping our animalistic nature in a more decent facade.

Postmodernity as a Refined Premodernity

The internet era has sent a segment of the population sprinting into postmodernity, but if you look closely, its underlying logic remains highly akin to the premodern.

Primitive humans fought over food, territory, and mates; modern humans fight over real estate, Big Tech job titles, and partners. In the past, we proved our worth in the tribe; now, we perform our identities on WeChat Moments, LinkedIn, and Instagram. The premodern era judged status by muscle, while the postmodern era has invented countless digital metrics: follower counts, annual salaries, height, academic degrees—even what movies we watch, what clothes we wear, and what music we listen to have become part of our personal brand premium.

From this perspective, the so-called postmodern is more like a highly refined premodern.

We have never shaken off our craving for status, resources, and reproduction; we have simply made the competition more abstract and efficient. Imagine a pack of wolves browsing for mates as if strolling through an exhibition, with precise stat panels and pros-and-cons analyses hovering above each wolf's head. Under such a mechanism, animalistic competition has actually been intensified to an unprecedented degree. Contemporary society's consumption and worship of the fresh, beautiful physical body push this contest to its absolute zenith.

But what makes humanity truly extraordinary is that we have started treating this competition itself as an object of reflection and critique. That is to say, we are not only slaughtering each other in the game, but we also possess the God's-eye view to scrutinize the game itself.

We critique consumerism, debate appearance anxiety, and reflect on how algorithms manipulate our desires. And it is exactly this capacity that pushes my deduction to the next stage. When a civilization is capable of reflecting on its own desires, it will ultimately gaze upon its most foundational code: reproduction.

The Fermi Paradox and Silent Civilizations

This leads to a grander, more desolate proposition: if human civilization is ultimately destined to gradually shed its biological instincts, what about other civilizations in the universe?

The universe is so vast, and there are so many stars, that the existence of extraterrestrial life, and even technological civilizations, is not an entirely unimaginable hypothesis. But if technological civilizations truly could have arisen multiple times, and if some of them eventually developed interstellar travel, automated probes, or even trans-stellar colonization, then according to the most basic deductions, the Milky Way should already be littered with their traces.

Yet, we have currently found no definitive proof of extraterrestrial technological civilizations.

Thus, we can't help but ask: if they exist, where are they?

This is the classic Fermi Paradox.

The Fermi Paradox naturally has countless possible explanations. Civilizations might be exceedingly rare; technological civilizations might easily destroy themselves; we might not have searched nearly enough; alien civilizations might use technologies we cannot recognize; or perhaps there is some "Great Filter" that makes the leap from the emergence of life to an interstellar civilization incredibly difficult to cross.

For a long time, we have perhaps been trapped in severe anthropocentrism: assuming by default that the more advanced a civilization is, the stronger its desire for expansion. We directly project Earth's logic of survival—survival requires resources, resources trigger competition, and competition forces expansion and reproduction—into the sea of stars. Consequently, our minds are filled with Dyson spheres, interstellar colonies, and galactic empires.

But what if a civilization is truly advanced enough?

When they have completely eradicated disease, aging, and energy crises, when they possess omniscient artificial intelligence and immersive virtual worlds that far surpass reality, why would they still want to colonize? Why must they relentlessly replicate themselves?

A primitive civilization must expand to survive; a modern state, bound by the laws of economics, also requires growth. But a civilization that has truly reached its zenith might finally ask the question we are only just beginning to realize: Why must I continue to reproduce?

If an exponential growth in technological capability is accompanied by a sheer drop in the desire to expand, then the more advanced a civilization becomes, the less it might resemble an empire, and the more it might look like a hermit devoid of worldly desires, or even a solitary ancient tree. They don't colonize the galaxy not because they can't, but because they have absolutely no interest in doing so.

This leads to an utterly absurd possibility: perhaps countless glorious civilizations have been born in the universe, yet after acquiring the power to conquer the stars, they simply stopped competing, reproduced less, and sank into the utopias of their own creation.

This is, of course, merely a thought experiment and cannot be considered a scientific answer to the Fermi Paradox. The paradox itself has no universally accepted solution, and "a civilization unwilling to expand" is just one of many possible explanations.

But when viewed alongside our previous reflections on population, it does evoke a fascinating connection. Humanity has only just reached the stage where we have the capacity to decide whether to reproduce, though we haven't yet completely freed ourselves from reproduction itself. What happens, then, if civilization continues to develop for another ten thousand, a hundred thousand, or a million years?

Perhaps the ultimate Great Filter is not nuclear war, nor AI annihilating humanity, nor some cosmic catastrophe, but intelligence itself. When a civilization becomes smart enough to no longer take "replicating itself" for granted, expansion grinds to a halt.

The reason the universe is so quiet may be because the pioneers who walked ahead of us eventually all chose silence.

We have been searching for civilizations that have conquered the universe, never expecting that a truly highly advanced civilization might simply no longer want to conquer anything.

Children of Men

Returning to ourselves. Humanity is not heading toward immediate extinction, because time is not evenly distributed on Earth. Some regions are still in the past, reproducing vigorously; some are stalled in the present; while the parts that have touched the future are already walking toward silence.

Our world may not spiral into the apocalyptic panic of total human infertility depicted in the movie Children of Men. But writing these words, I am ultimately harboring a trace of underlying worry. Reproduction is so special because it is not just biological continuation, but the anchor of meaning. No one wants to live in a world devoid of hope, a world where you can only listen to a countdown ticking away.

I have always believed that bearing and raising the next generation is a crucial puzzle piece in the completion of the human mind. Without experiencing this shift in identity, a person's life experience might lack that overwhelmingly profound sense of responsibility, attachment, fear, and courage.

As Cliff Unger said in the game Death Stranding when recalling becoming a father for the first time: "I was always scared of making a mistake, scared of falling... but your arrival made me brave."

Though not yet a father myself, I can truly see this invincibility born out of vulnerability in my own parents, relatives, and friends.

Another line from Death Stranding perfectly interprets the meaning of reproduction: "Children are our bridge to the future."

I hope that humanity can ultimately be like the ending of Children of Men—passing through the fog and despair, to a place called Tomorrow, where the joyous laughter of children can still be heard.