Misunderstanding Malthus’ mistake | Hacker News Reader

Misunderstanding Malthus’ mistake

andrewbatson.com

43 pointsbesmirch30 comments

> Something clearly operated to keep human population in check before its explosion over the last couple of centuries. But it was generally not starvation. The real problem is that population growth begets population density, and population density, in the absence of sanitation, antiobiotics, and other checks on infection, begets disease and death

That's an interesting opinion, but how does that model explains why eastern Asian countries (where rice was available) where able to achieve and sustain far higher population density than areas fed by wheat?

Also, pre-modern cities like Rome or Baghdad where much more densely populated than the average and have seen such population level for centuries, which means than population density in the rural world was far lower than some hypothetical limit level.

The article does say that Rome required some level of constant migration into the city to maintain it's population.

I can't speak to how true that is but it might explain the population numbers.

I think that's perhaps rather generically true for premodern times. I've seen estimates of mortality rates for medieval England that have cities consistently higher than rural areas, so you'd have to have migration to the cities.

And let's not forget that malnutrition causes disease.

> Asian countries (where rice was available) where able to achieve and sustain far higher population density than areas fed by wheat

Do you have any sources/data for that point? I’m curious why rice would impact population density differently than wheat.

Sure: https://acoup.blog/2020/09/04/collections-bread-how-did-they...

As usual with Bret Devereaux, this is quite a long read.

When people are chronically malnourished and undernourished, they succumb to one of the many diseases swirling around. Infectious diseases or deficiency diseases or parasites.

Periods labelled "famines" were not all that common, but much of the population was living in a sub-acute famine much the time, primarily for political reasons (power imbalances, unelightened decision-makers).

> how does that model explains why eastern Asian [rice-growing areas] ... where able to achieve and sustain far higher population density [than the Eurocentric examples in OP].

The average densities were higher, but until the 20th century, with Beijing* as the primary exception, big cities were in Western Asia, North Africa, and Europe.[1] Many infectious diseases probably need "point" (small area) population sizes greater than those of the villages prevalent in rice-growing areas to take hold.

Rice rulers could afford to burn a village to the ground if there were reports of spreading sickness in it. They'd only lose a small fraction of their tax base, which would soon be replaced. Rulers of large cities, not so much.

Why did rice-growing areas have villages while wheat areas developed cities? I don't know. Possibly something to do with wheat being being grown in drier areas so it could be stored for years without rotting, making large centralised granaries possible.

* And a few other North China cities. I know very little about Beijing, but I don't think the climate there is suitable for rice.

1. https://en.wikipedia.org/wiki/List_of_largest_cities_through...

> until the 20th century, with Beijing* as the primary exception, big cities were in Western Asia, North Africa, and Europe > Why did rice-growing areas have villages while wheat areas developed cities?

I'm sorry but that's simply untrue. There were lots of cities in premodern China. Urbanization probably got started earlier in the Near East, which is why you get early large cities there, but even in the list you link to, from ca. 1000 BC on there are basically always one or more Chinese cities in the list: Haojing, Luoyan, Xiadu, Chang'an/Xian, Nanjing, Kaifeng, Hangzou, .... (And this is ignoring other large cities that were never the largest like Guangzhou.)

(Beijing doesn't become really significant until the Mongol Yuan dynasty makes it their capital in the 13th Century.)

Sanitation practices may have been more developed in the denser regions of Asia than they were in post-Roman Europe.

Anecdotally it feels that way (bathing, certain food handling and disease rituals) from reading historical accounts. I have a parent from each and when they talked about their childhoods (1930s and 1940s), even through war, the differences are stark. But I’m hardly a scholar so this is anecdotal.

Here I was hoping that this would be about Verhulst's improvements to Malthus' work. Verhulst's logistic equation still gets used today.

If you were to state what Verhulst’s insights were, you might start a conversation about this.

Apparently they are these:

https://en.wikipedia.org/wiki/Logistic_function#In_ecology:_...

The original conversation happened almost 2 centuries ago I think (1830's). But sure!

I think we throw away the baby with the bathwater when we say "Malthus was wrong". I think it's better to say "Malthus inspired the beginning of an awesome idea".

Malthus' original idea was where he plotted population growth and food production in the same graph. When the 2 lines crossed, that's bad.

That's obviously not very realistic, but actually he had the gist of it; it just needed a bit of refinement.

Not much later, another Belgian by the name of Verhulst did indeed improve on Malthus' model. He came up with a formula where at first the population grows exponentially; and then later it slows down before it reaches the limit (carrying-capacity). In Verhulst's model, you don't have a catastrophic line-crossing.

At that point, you basically have an actual Minimal Viable Product that you can use to predict and think about real-world population dynamics, and a whole lot more besides.

Over the last two centuries people have built a lot of discoveries on top of that.

This Veritasium video is about one small (but awesome) bit of that: https://www.youtube.com/watch?v=ovJcsL7vyrk

It's a good thing not everyone thought Malthus was (completely) wrong!

Hmmmmmmm! I didn't know about Feigenbaum's constant.

That is interesting and mysterious...

That’s all you have to say? ;)

It might take a lot of processing before my brain can integrate this information well enough to formulate the next question!

What strikes me at first is that if this pattern is universal... then... well, it means that the THINGS that we think about - the exceptions, the problems that people encounter in their work and in their personal lives, come from fundamental aspects of numbers.

e.g. the power engineer who has to deal with spikes and outages; the pcb designer who has to deal with interference and cross talk, the plumber who has to diagnose a shaky pipe in an old building; the network engineer who can't fully explain latency; the spouse who can't synch with their partners mood; the athlete who surprises every now and then; the baseball team that should be winning but isn't...

And more specific to the topic, I wonder how world and country population forecasts are made. Do the models take account of Verhulst's dynamics?

What do weather forecasters know about this?

> Ronald Barrett and colleagues from the Department of Anthropology at Emory University in Atlanta have gone as far as to suggest that the emergence and re-emergence of disease threats owing to globalization and antibiotic resistance is a sign that we’re entering a “third epidemiologic transition” comparable to the rise of infection at the dawn of civilization and its fall in the last century and a half.

That is an ominous prediction. This coupled with climate change makes the future look pretty bleak. No wonder Bill Gates works so hard on these problems.

London was pretty dense when the black death reduced the population. Disease had not prevented it from reaching that density.

A problem of more land under cultivation is food transport.

Another mechanism of population control is warfare. A predisposition for war, and conquest of land, avoided food shortages in the first place - for the victors. In short: the Four Horsemen of the Apocalypse maintained carrying capacity. Another, rarely practiced, was infanticide.

This is increasingly being solved with contraceptives. Note that TV, internet, video games, wealth and education have contraceptive effect.

> Another, rarely practiced, was infanticide.

Rarely practiced? Infanticide was extremely common in all premodern societies.

As a complete layman, with no study in this area, his description of a reservoir made be think of oil. Our current technological progress is heavily dependant on oil - not just for cars, but more importantly cargo ships, trains and aircraft. At some point hundreds of years perhaps from now, it will run out. And that may change the equation somewhat.

We are currently running out of atmosphere to dump the CO2 from burning the oil into.

That's an interesting way to phrase it. If the atmosphere were going to saturate in a way that would prevent combustion from even happening that would be a very interesting scenario.

if you are thinking along the lines of atmosphere saturation to a point of not being able to support combustion, then i guess "living" organisms who depend on oxygen would be long gone by then

The CO2 content of the athmosphere is actually not that high, nor will it be at the end of the century even if we don't reduce global emissions. The problem is that it is quite enough already to cause climate change. Which would also not be such a big deal if not coupled with large-scale destruction of ecosystems and our dependence on non-renewable resources.

I didn't literally mean the atmosphere had a limited capacity to hold this much CO2 and no more.

Please add "without existential-level consequences", which was the implied meaning.

Considering that our predatory rampage of resource extraction has brought our ecosystem to the edge of collapse, I'm not convinced that Malthus was wrong.

Let's revisit this again in 50 years when we've stabilized our population and don't push earth day forward with every year.

This isn't a refutation of Malthus at all.

He didn't say that food production couldn't increase to keep up with population, he said that it couldn't do so *forever*--and nothing has changed about that.

What avoids a Malthusian doom is birth control.

Calling Malthus wrong may be slightly better than Fukuyama's "The End of History and the Last Man" https://en.m.wikipedia.org/wiki/The_End_of_History_and_the_L... I mean people love to extrapolate from the recent trend. Genes compete not on a time scale that individuals likely appreciate. Yes for us mere mortals we will all be dead in the long term so the outcome may be immaterial. But I wouldn't bet against math in the long term even if no one now alive will be around to collect the winnings.

That very first sentence is very misleading. Malthus was not wrong - he was right given the set of assumptions made at the time. There is a difference.

The article goes on in some detail to make the case that even by your belabored definition of wrong, Malthus was wrong. It was never—or rarely—food that limited human population, but disease.

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