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Comment by arcticbull | Hacker News Reader

> In a world that you have both developed and developing countries, the stable equilibrium seems to be world suffering.

I think that's the wrong read.

All sorts of animal population follow a sigmoidal growth pattern where there's exponential growth, some degree of overshoot and then a return to a steady level somewhat below that peak.

I think it's more likely, drawing from biology, that we end up at a stable global population level without having to worry about moving backwards along the metrics of education, income or contraceptive access.

Remember it was just a few years ago everyone was absolutely terrified that we would grow to the point where the world simply couldn't hold us all and we'd die off -- and now we're terrified the population will zero out. In reality, neither is very likely. We're probably just going to chill around 8 billion or so until/if we go multi-planetary.

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It's very dangerous to try and compare human behavior to any pattern seen in nature— particularly human behavior in aggregate. While humans are animals like any other, we are also very much not simple beasts beholden to environmental conditions.

To wit: the current human population is beyond the natural carrying capacity of the places we live. The only reason we can sustain 7bn people today is because we've artificially increased local carrying capacity through artificial fertilizer. If we lost that technology today, a majorty of humans alive now would starve to death.

There's really no reason to assume any environmental factors that don't physically preclude human occupation will have any effect on overall population numbers. We can artificially extend our ecosystem to support essentially unlimited people. The only real hard limit is space to physically put bodies and the amount of energy our society can use without boiling the oceans with waste heat.

If population growth levels out, it won't be for any natural reason because we are already well beyond any natural limit.

But we are beholden to environmental conditions! All of our technology, including the base materials for artificial fertilizer come the environment. The unique thing about humans is the inter-dependence. We need people specialized in tasks to keep everything running. This requires the use of 'money' in whatever form to do the bookkeeping on distributing resources. I think what we are seeing is that the 'money' aspect our human interactions seems to be key constraint on people having more babies.

I think the real problem is the age structure of the population is increasingly skewing older and this problem becomes worse the lower the birth rate. I don't know how we're going to keep supporting more and more people getting past the retirement age and collecting benefits on a shrinking working age population being squeezed harder by taxes. Either retirement spending goes down maybe with higher retirment age or increased healthspan, or we become much more efficient at taking care of the elderly with fewer resources, or the working class gets squeezed harder & harder.

There’s also the option of raising corporate and high-net-worth-individual tax rates!

> I think it's more likely, drawing from biology, that we end up at a stable global population level without having to worry about moving backwards along the metrics of education, income or contraceptive access.

There's absolutely no inherent equilibrating force that will stabilize global fertility rates at replacement. Many countries have blown by replacement (the USA included) and continue on a downward trend year over year.

And if even cultural norms were reversed to pro-birth, it wouldn't be enough to reverse the trends, as the decline is compounding, and the increase of average age produces other complications (hard economic issues for starters, making people even more hesitant).

Yea my crackpot theory is it’s genuinely something that’s inherent which is causing these declines. That’s why no attempts to reverse them have been successful. I think like you’re saying we’ll end up at some equilibrium.

Actually growth patterns of animals vary wildly. There's a whole set of animals that get "unstable" growth - Cats are famous for this, for example. That means that cat numbers in specific areas actually grow to the point that cats die out in the next generation, destabilizing the entire food chain in the process (happened in Australia, for example)

The problem with this instability is that the numbers bounce around wildly. Up and down, by a lot, in as little as 2 or 3 generations. But there's a process that stops the bouncing: hitting zero.

Cats are kind of crazy as an invasive predator: they can be sexually mature after 6 months and have litters of up to 6 kittens every 3 months.

Obviously that's more at the upper end, but for an obligate carnivore that is an amazing multiplier.

They are small carnivores, I imagine their wild ancestors were kept partly in check by even larger carnivores eating them?

>All sorts of animal population follow a sigmoidal growth pattern where there's exponential growth, some degree of overshoot and then a return to a steady level somewhat below that peak.

Animal populations usually decline because they lack food or have predators and other external factors. Not usually because of a lack of will to reproduce due to social or economic reasons.

I don’t think we’re going to find a number and stay there. Too many factors impacting population size are changing. Healthcare, climate, food science, etc. It’s likely to always fluctuate, and it’s likely to continue to be something people worry about.

The economy depends on some level of growth, so if we can't accomplish that with a stable or shrinking population then it's gonna be a bad time for a while.

EDIT: I did not think I'd have to state this explicitly, but:

yes, I am in fact talking about the capitalist economy the western world currently operates under

growth = economic growth

The economy does not depend on population growth. It depends on productivity growth.

Why does the economy require growth? Biological systems can find equilibria, why can't an economy do the same?

Because bigger number, obviously.

All economies do not inherently rely on growth. It's just that capitalists have brainwashed themselves into believing capitalism is the only type of economy possible and that growth can go on without bound literally forever.

It's exactly as stupid as it sounds.

Capitalism requires growth. If your sales aren't growing your stock price goes down.

Economy in general doesnt require growth.

The economy we were born into, the level of material production, business, amenities etc and how we run things, does.

It can find an equilibrium at some point, but it will be blood and people who think they should have robot servants and food delivery wont like it. As for the time it will be achieving that equilibrium, it will be painful.

By "economy", I presume you mean things like real estate speculation.

Japan is a good example of a country where the population has been in steady decline for a long time now. The economy has stagnated, but it has not collapsed.

The more worrisome part of what we're seeing in Japan is the total hollowing out of the countryside as the young systematically pack into the three large cities that increasingly dominate all economic activity, namely Tokyo, Osaka and Fukuoka.

Why is rural depopulation worrisome? Young people, as one would expect, want to be located near other young people and jobs.

Because that's where the food comes from.

Are they producing less food? Migration from the country to the city has been going on for a long time. You just don't need as many people to produce food as you used to.

Increasing the high-density urban population leads to even lower fertility.

"We find a robust association between density and fertility over time, both within- and between-countries. That is, increases in population density are associated with declines in fertility rates, controlling for a variety of socioeconomic, socioecological, geographic, population-based, and female empowerment variables."

https://pubmed.ncbi.nlm.nih.gov/34914431/

This is inevitable.

The Steep Curve to Peak Urban - https://news.ycombinator.com/item?id=45265342 - September 2025

> Cities are engines of productivity, trade, innovation and prosperity. We’ve built, re-built and expanded in cities because they bring us closer, offer us greater access to jobs, services, ideas, opportunities and experiences. They make us overall wealthier and healthier, as long as we invest in addressing the side effects and unintended consequences of urbanization.

https://population.un.org/wpp/

These young people will be middle aged people located near old people, with a huge average age - and the flee to the cities will increase that.

>Japan is a good example of a country where the population has been in steady decline for a long time now. The economy has stagnated, but it has not collapsed.

Give it time. Japan only crossed the point of deaths > births about 20 years ago, which was also the time it reached peak population (as recorded by a census around that time).

Give it 20 years for the peak kids to grow above 40 and it will be a dystopia.

The economic paradigm that evolved during the exponential portion of population growth depends on it. It's not the only model that can possibly exist, and it looks like we'll be meeting new ones.

"bad time" is relative. Perhaps the lifestyles of the West are simply fundamentally unsustainable.

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