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Comment by danbruc | Hacker News Reader

Some of the most spectacularly wrong predictions in history have been made by those who claim that overpopulation is going to swamp the planet. Thomas Malthus, a British economist writing in the late 1700s, is the most famous of these. Extrapolating past trends into the future, he predicted that population growth would inevitably swamp available food resources, leading to mass starvation. That didn’t happen - we continued to develop new technologies that let us stay ahead of the reaper.

Why are people so eager to point out that Malthus was wrong all the time? As far as I can tell he was not. He said if population growth continued as in the past, then we would starve, not that we necessarily will. I also think it is wrong to say we engineered us out of starvation, at best it bought us some time to get the fertility rate down. As the article admits, exponential population growth can never be finally solved by technology.

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Because he believed that population would be limited only by resources, and that fertility rate was nearly invariant. These have both proved to be wrong. The popular imagination of the Mathusian prediction of inevitable mass starvation (which is not really that mis-characterized) was also wrong. So classifying him as wrong seems fair.

Well, he got wrong how the fertility rate would evolve, but that does not invalidate the model he developed. And he would probably have been pretty spot on with his predictions if the fertility rate had not drastically decreased.

> And he would probably have been pretty spot on with his predictions if the fertility rate had not drastically decreased.

If I went around saying, "well, I would have been right if that one part of my theory hadn't become invalidated by events on the ground" people would think me impossible to reason with.

Not if your theory became a meme that influenced people's behavior.

Consider if we were to somehow diffuse the climate change bomb thanks to policies put in place based on current models. Our collective behavior would influence the outcome, but it doesn't invalidate the predictions.

In fairness, it would have been very hard for him to predict the decrease in fertility; it relies on both technological (birth control) and social (womens’ rights, pensions systems, and various others) innovations that would not have been reasonably predictable at the time.

And yet, the specter of a possible Malthusian catastrophe may have helped motivate us to prevent it. I don't really call that being wrong.

The specter of a Malthusian catastrophe was what motivated Adolf Hitler.

The factors that ended up defusing the Malthusian catastrophe were not influenced by Malthus at all. We did not go about educating women because of Malthus.

Good Godwin.

Simply mentioning Hitler or the Nazis is not a reason to invoke Godwin's law.

Godwin's law simply states that Nazis will eventually be mentioned (with probability approaching 1).

Also, he's completely wrong. Hitler's reasoning was not to avoid a malthusian catastrophe. Pretty surprised people here bought that.

The goal of the Nazis was to conquer eastern Europe, remove most of the existing population, and resettle it with German colonists. The rationale was to feed and support a growing population, which is an idea at least reminiscent of Malthus.

The rationale was that their own ethnic group deserved to prosper at the expense of others. The idea that germany might be in danger of running out of food via population growth was not present. If by "reminiscent" you mean "has something to do with population" then sure, it's reminiscent.

Population remains limited by resources. How could it not be? We've been adept over the years at finding new resources or extending old ones (the expansion of ranching and farming in the Americas in the 19th century, which greatly increased the global food supply, or the invention of artificial fertilizer, for instance), but it is a bit of hubris to say that this is a solved problem for all time.

Population is not only limited by resources. There are many places where humans reproduce at a rate well below what resources can support.

It is a ceiling, but there are so many signals prior to hitting that ceiling that the simplification of the Malthusian growth model does not seem to have any utility.

Take for example US population density west of the Mississippi. No one needs to explicitly die of thirst. If water is the limiting factor, the cost of water is invisibly incorporated into nearly every cost people experience. If there were limitless water, the influence of other constraints would simply rearrange.

After reading the comments here it probably boils down on what you focus. If you see the entire work pointing out the unsustainability of exponential population growth that will come to an halt either by positive or preventive checks, then you will probably not call him wrong. If you focus on his view that people will probably not be able to get the fertility rate down to sustainable levels and that a Malthusian catastrophe is therefore probably inevitable, then you will most likely call him wrong. But as I said before, I didn't read much of his work and therefore I might have a misconception about what points he actually stressed the most.

Population remains limited by resources.

No, it's not, and that's what's so surprising. As nations become wealthier, the birth rate goes down, not up. And it goes down by a lot; more than 50%. All the way down below replacement rate.

The US passed "peak baby" in 2007. Outside of Africa, all the major world regions are past "peak baby".[1] Population seems likely to level off around 2050.

[1] https://ourworldindata.org/fertility-rate

> it goes down by a lot; more than 50%. All the way down below replacement rate.

Some quick systems-level analysis shows that this state of affairs cannot possibly be stable. Societies reproducing at below replacement rate are quickly replaced by societies reproducing above replacement rate. What will happen then?

Counting on societies to hold their birth rate down that far is fundamentally at odds with the theory of evolution. It's not a good basis for predictions of the future.

Societies reproducing at below replacement rate are quickly replaced by societies reproducing above replacement rate. What will happen then?

By then, the robots will be ready to take over.

> Counting on societies to hold their birth rate down that far is fundamentally at odds with the theory of evolution.

Why?

Because anything reproducing at below replacement rate goes extinct. If you e.g. look around at any given point, and take a sample -- by any method -- of living things that come to your attention, none of those things will have gone extinct.

It's the same reason there are no societies which abstain entirely from giving birth. There have been a few, over the course of history, but they disappear for the incredibly obvious reason. At a steady state, such societies don't exist because they can't exist.

It sounds to me as if you are simply taking the Malthusian fallacy and reversing it to make another fallacy. Certainly, a population that continues indefinitely below replacement rate will go extinct. That's not terribly likely though.

What did I write that you're responding to? It looks like you're agreeing with everything I've said.

As countries develop both their birth rates and death rates decrease, but below replacement rate is a pretty strong statement. Population growth like this is modeled in the Demographic Transition Model and consists of 5 stages. Most developed nations fall in the fourth stage, with stable birth and death rates. The 5th stage is often debated, but a pretty good example would be Japan - a country with an aging population and low birth rates (learned about this in school several years ago though, not too sure how up to date)

In Germany there is not a single(!) district with above-replacement rate. Only certain demographics (migration background) have (much) higher rates.

> Societies reproducing at below replacement rate are quickly replaced by societies reproducing above replacement rate.

“Societies” are about memes, not genes, and humans are powerful imitators of things that visibly are associated with success.

You could model a "society" after early modern France, following these stylized facts:

- "Society" is divided into two cultural subgroups, Catholic and Protestant.

- Protestants reproduce below the replacement rate.

- Catholics reproduce well above the replacement rate.

- Protestants nevertheless persist in the population, because the children of Catholics are relabeled Protestant at very high rates.

However, for this to work, note that the reproduction rate of all France, including the Catholics and the Protestants, must be above replacement.

(I will note that I have no opinion on whether, in the real France, Protestants actually reproduced below replacement or just below the level of Catholics. The usual question you see accompanying these facts is "how could there be a significant number of Protestants in France?", not "how could there be people in France at all?")

Fine, but the future still belongs to those who show up. Evolution need not be about DNA. Memes (such as religion) will do the job just fine. Those who think "success" involves low reproduction are taking the evolutionary off-ramp to extinction. Those who do otherwise are selected for. They have the correct memes, or genes, or whatever -- the mechanism doesn't matter.

> "the mechanism doesn't matter"

Makes me think about this old article in ForeignPolicy I read. I could interpret his provocative statements about the success of patriarchy as a sort of "correct meme" to borrow your terminology. Interesting thought. http://foreignpolicy.com/2009/10/20/the-return-of-patriarchy...

Except of course that the meme that is "currently showing up" is that lower human population is not a bad thing".

It's basically a race: will infertile memes infect fertile cultures before fertile cultures outbreed infertile cultures?

It's too early to call a winner. If you want to see some early hints, you might want to focus on populations that have very high fertility but are otherwise well-integrated into the prosperous, developed cultures that are experiencing low fertility overall. Mormons, for instance.

> Societies reproducing at below replacement rate are quickly replaced by societies reproducing above replacement rate.

Yes, and it is already something that is setting of early warning signals around the world. Countries like Japan and Sweden are looking at major catastrophes in the coming decades if they can't get their populations to increase their birthrates. Its a large part of why Sweden has some of the best benefits for new parents on the planet.

Additionally, some see the collapse of stores like Toys R Us as the first wave of economic effects resulting from the declining birth rate in the US (note that Toys R Us also owns Babies R Us). Obviously, there are lots of factors at play, and retail in general is doomed, but a greatly reduced market for babies and children's products is indicative of a potentially greatly reduced market of everything else in the coming decades.

> Additionally, some see the collapse of stores like Toys R Us as the first wave of economic effects resulting from the declining birth rate in the US (note that Toys R Us also owns Babies R Us).

Toys R Us's collapse was mostly caused by a leveraged buyout in 2005.

http://www.latimes.com/business/la-fi-toys-r-us-leveraged-bu...

Exponential growth must always come to an end, but if your biggest resource is people than more people can overcome other resource limitations by invention and culture.

Because he was wrong.

It's true that if human population on Earth grew to the point where there was no room for one more human on Earth, then we'd have huge problems. But this is a) very bloody obvious, b) exceedingly simplified, and c) misses the whole point of what actually happened and what others predicted would happen: that population would stabilize (and even fall, perhaps dramatically) long before we might starve from lack of room to make food in.

First of all, there have been huge advancements in food production technology in all the years since Malthus. Second of all, there are huge advancements in the pipeline (basically indoors vegetables growing with minimal food waste and extreme space-efficiency, and lab printing of meat). Third, we clearly want fewer children when infant mortality is low and life expectancy high. Malthus could not have foreseen all of this, but he certainly lacked imagination, and worse: malthusians in the last 100+ years really didn't need that imagination, just normal powers of observation, and STILL they have all missed how wrong malthusianism was.

"But still, he was right!" No, he wasn't. We could grow and grow and grow if we get off the Earth -- hard to imagine that at this time, but maybe not in a few hundred years. "But we could run out of habitable planets in the Milky Way!" Well, yes, we sure could, but I think that's just not something we should worry about today and for thousands of years yet.

Q: Why are there any malthusians? A1: Because humans appear to be wired to be pessimistic and alarmist. A2: Because humans appear to be wired to be pessimistic and alarmist, which means that cynical people / psychopaths can take advantage of the rest of us. Doesn't make Malthus right.

> First of all, there have been huge advancements in food production technology in all the years since Malthus. Second of all, there are huge advancements in the pipeline (basically indoors vegetables growing with minimal food waste and extreme space-efficiency, and lab printing of meat).

These are not good counter-Malthusian points. There were huge advancements in food production technology all throughout history (ploughs / iron ploughs / crop rotation / plants from the new world... the list really is endless), but things were in a much more Malthusian state.

The non-Malthusian state of affairs we enjoy today is entirely a function of people choosing not to have children, not a function of better technology. People who were so inclined could easily wipe out (per capita) the gains from productivity, by increasing the number of capita.

Most of the tech improvements came well before population growth curve flattening. It's quite clear that we develop realistic technology that we need. It's also true that if we didn't naturally (i.e., without force) reduce population growth by now that we'd be in trouble (there would be no getting off the planet fast enough to prevent collapse), but the tech came first, not the other way around.

> There were huge advancements in food production technology all throughout history

The current world population could not be fed without Nitrogen fixation and synthetic fertilizers. The Haber-Bosch process is a huge counter-Malthusian point by itself.

No, it isn't, because it's a productivity technology and those are not relevant to the Malthus dynamic. You know what had a massively larger impact than the Haber-Bosch process? Agriculture.

But the development of agriculture made the world more Malthusian, not less.

In contrast, the Black Plague made Europe much less Malthusian by the simple expedient of killing maybe one person in three. This made everyone more productive without any accompanying technology gains. But the point isn't the productivity gain - it's the population drop.

>It's true that if human population on Earth grew to the point where there was no room for one more human on Earth, then we'd have huge problems. But this is a) very bloody obvious

And also a strawman. We can have huge starvation crises, and struggles for power, migration etc with much much less population, even 2x the current number can yield catastrophic power struggles.

>Q: Why are there any malthusians? A1: Because humans appear to be wired to be pessimistic and alarmist. A2: Because humans appear to be wired to be pessimistic and alarmist, which means that cynical people / psychopaths can take advantage of the rest of us. Doesn't make Malthus right

Actually you've got it backwards. We're wired to be pessimistic and alarmist so that fewer cynical people / psychopaths can take advantage of the rest of us.

If we were optimistic / eager to believe we'd be far worse.

>If we were optimistic / eager to believe we'd be far worse.

That is an awesome thought, I always like how there's almost a bias in things we consider which always center around, I'm not sure how to articulate it, but center around things that have been demonstrated.

Consider something like gun deaths, a very tangible concrete easy to measure indisputable thing. Yet the possible outcomes from alternatives that have not yet been demonstrated is always a complex hypothetical thing. In the gun example how many folks have been saved because of guns, etc. That's not an easy metric to measure by any means because where do you draw the line and what examples to include, etc.

Exciting stuff to consider what a system would be like out of tune from the current backdrop of being tuned a certain way that we take for granted and maybe never even notice. Definitely welcome anyone to comment and develop these thoughts or share some formal concepts in this space.

I feel you just described a core reason that many people are conservative. Even if they don't know it. The risks of the hypotheticals outweigh the potential benefits.

No, being pessimistic means being vulnerable to those who preach that the sky is falling. Not always, obviously. For example, Churchill spent the 30s isolated and ostracized for doing just that, but he was right. Appeasement in the 30s is a bit of a special case though: to believe the sky was falling was to believe that war was needed, and no one in Allied countries wanted war after the Great War -- there was a greater pessimism about war than there was about Hitler and Nazi Germany.

Malthusianism has been wrong for centuries, and people still buy that garbage. This is because people are born every day and want to believe the sky is falling. Most eventually grow up.

Only people in first world countries who have not experienced difficulties due to overpopulation , poverty etc. claim that Malthus is wrong, everything would improve etc.

Having been brought up in an average Indian family and looking at the future where we have a population which is sky high and even though the fertility rate is significantly lower today, you can see the problems first hand. There are no easy solutions now, that time is gone. Only crazy future looking practical things like what the Chinese did with 1 child policy when it was needed long time back would've had helped.

People should get out of their Western bubble, live in overpopulated cities in Bangladesh/India, travel in their public transit, try to find a job as a local without connections and then report back whether overpopulation is not an issue.

European cities in the 1600s were massively over-populated for much of the same reasons non-Western cities are massively over-populated now: The rise of industrialization, a lack of available housing, poor infrastructure, and massive population growth coupled with rapid urbanization of a traditionally agricultural workforce.

London, as just one example, was an ugly, disgusting, miserable place until the mid 20th century, so it takes time to sort these things out. Cities in India might be a mess today but once their population growth simmers down and the cities can get better organized they'll be much less crowded.

As filthy and disgusting as the slums of some cities in India are, London was worse. The Thames was so polluted with sewage that paddle boats would churn it into this vile froth, like bath bubbles from hell. People who fell overboard from boats would drown because they couldn't be seen through all the foam. Even though the Parliament buildings are right on the river, and the smell in the summer was absolutely unbearable, it took decades for a proper sanitation system to be built because of a lack of political will.

Better infrastructure means you can even out the population density better. India, like many other industrializing countries, is way behind the curve. China is one of the few that's been building infrastructure like its going out of style. It's not the one child policy, but aggressive city engineering that's keeping a lid on the problem.

I think the problem is, no one predicted that educated women, the accessibility of family planning aids, and economies developing [1] would be so effective at reducing fertility rates (with that said, it would've been convenient if this occurred earlier in the 20th century; we're going to hit 11 billion people before the population decline is in full swing, and that's going to challenge the carrying capacity of the planet).

Were these unintended consequences? In most countries, yes. Humanity keeps turning up lucky in this regard (the above mentioned outcome, solar and wind becoming cheap enough we might be able to go carbon neutral for energy consumption, etc).

[1] PDF: http://www.earth-policy.org/images/uploads/book_files/ecoch1...

I admittedly did not read »An Essay on the Principle of Population« in its entirety, but that may actually be the point where he was the most wrong. He could not imagine the fertility rate to fall as much as it eventually did and therefore did not really expect that disaster could be avoided. But I still think it is rather misleading to turn this lack of imagination on his side for the evolution of this - of course extremely important - one factor into calling his work wrong and disproven.

I don't believe his work was wrong. He made the best prediction possible with the data available at the time.

I did not want to imply that you called him wrong, this was still aimed at the often repeated narrative that history has proven him wrong.

But his conclusions turn out to be flat-out wrong.

Forecasting is not always accurate.

Economies can also undevelop, leading to inceased fertility rates.

There’s less evidence for this; once fertility rates drop, they mostly seem to stay dropped. A notable example is the former Soviet Union.

~9 generations hence it's hardly safe to say those predictions are bunk. We may have found some short-term patches, but conventional food production today is deleterious to soil stocks. We're hardly secure from the possibility of famine this century.

I think he was simply bad at functional analysis compared to current understandings. The output of growth functions with multiple inputs tends to look like a logistic function when inputs change and the output shifts to a new equilibrium. The front part of a logistic function looks like an exponential function.

World population is probably ten times what it was at the time his growth model was proposed 220 years ago. That is so far below the rate that humans could multiply their numbers, that it doesn't make any sense that people have argued that we were saved by technological advances. Technology seems to change carrying capacity, then human population approaches that carrying capacity rather than catastrophically hitting a barrier and suffering famines.

Nature abhors a true exponential nearly as much as it abhors a vacuum.

All the world's a sigmoid.

People are uncomfortable with Malthusian conclusions when applying his model to other systems. Malthus highlighted a tension between the relative sizes of populations in certain resource-allocation games wherein a population both wants more members but also wants more resources per member.

> As the article admits, exponential population growth can never be finally solved by technology.

Only in the sense that maintaining a population in the first place can never be finally solved by technology. Otherwise, I'm pretty sure the universe has more than enough energy and matter to support as many meatbags as we could ever want.

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