Spoilers ahead, I guess?
Thanos, the big purple Marvel villain, became a big hit in popular culture after appearing in MCU movies, with an encore performance of very successful internet memeing. His shtick is that growing populations lead to overcrowding in the universe, and the best policy tool we have at hand is to murder half of all sentient beings1.
I find it encouraging that MCU writers made the decision to cast Thanos as a bad guy who has to be stopped. I also condemn murdering half of all people! But while he’s definitely a villain, he’s sort of a sympathetic villain, someone who has identified a real problem but is just being too evil about it. And I take issue with that — killing half of all people to stop overcrowding isn’t just evil, it’s also plain stupid.
Thanos was probably reading Malthus
The intuition that having population growth outpace available resources has been around forever, but it was Thomas Malthus who first formalized it as economic theory. Malthus was born in England in 1766, at a time when huge swathes of the population were genuinely very poor, as in “having enough food most of the time but not all the time” poor. The critical bit of theory he introduced is the notion that increases in food production only produced temporary gains in welfare, because the abundance of food would cause people to reproduce more, getting everyone back to abject poverty. This is grounded in two key assumptions:
We can’t increase farming productivity very quickly
People who aren’t close to starvation will reproduce aggressively
Unfortunately for Malthus, these two things stopped being true, sort of unpredictably, after he died. To illustrate farming productivity, look at this chart of wheat yield per hectare in the UK:
Malthus said that increases to agricultural productivity are generally linear, which if you cover everything past 1830 with you hand, you can see how he got there. But starting in the early 1900s we experienced the Green Revoluion, a hugely underrated era in history when we started producing a ton of food.
Meanwhile, population trended in the other way. Malthus proposed that population growth, in the abundance of food, was exponential. But going forwards, it was actually linear!
And note that this is still overstating population growth since a lot of this is immigration, not births. For somewhat mysterious reasons that have as much to do with culture than with economics, once people reach a certain level of wealth people start having way fewer kids.
The formal measure of how many kids people have is the ‘fertility rate’, the average number of children born to each woman. Japan, famous for below-replacement-rate births, had a fertility rate of 1.3 in 2021. But this is old news it turns out — South Korea clocks in at a staggering 0.88, China at 1.16. The club of countries that have below replacement fertility includes the United States (1.66), Chile (1.54), Germany (1.53), and Iran (1.69), amongst many others. Declining fertility in the face of increased wealth seems to be a constant phenomenon across different continents and cultures.
We don’t need murder
I didn’t actually write this essay to dunk on Thanos — you don’t have to dig up 18th century philosophers to find inconsistencies the plot of a MCU movie. I think the reality here is that ‘Malthusian intuitions’, if you will, run pretty deep. The 1960s saw a huge revival of these ideas — The Population Bomb was published in 1968, kicking off another overpopulation panic. If you look at the above charts, we really already knew better by the sixties, but nonetheless the first editions of the book opened with:
The battle to feed all of humanity is over. In the 1970s hundreds of millions of people will starve to death in spite of any crash programs embarked upon now. At this late date nothing can prevent a substantial increase in the world death rate...
This did not happen! The book is full of apocalyptic predictions like this, nearly all of which proved to be comically incorrect.
I think this book’s lessons have become deeply embedded in the American psyche, even though most have never heard of it. It matters that more people realize how thoroughly discredited all of this is. If we knew better in 1968, we definitely know better by 2023. I haven’t seen anyone actually propose implementing Thanos’s population controls (thankfully), but discussions about population are now extra-relevant in light of declining fertility, and it would be a mistake to think of declining fertility as a good way to prevent people from starving.
But climate
I don’t want to make light of the burden that human activity places on our planet. It would be a hot take to claim that either a.) humans don’t adversely impact the environment or b.) more humans doesn’t make the impact worse, and I’m not here to argue for either.
If you’re concerned with the growing human population from this angle, I’d instead propose considering these facts:
As countries become richer, people tend to have fewer kids
A sizable portion of countries are rich enough that they’re below replacement rate at this point
There are still a bunch of poor countries out there with much higher fertility rates
Which is to say, human development matters! It matters of course because eradicating global poverty is a really good thing to do. But it also does seem to reduce birth rates.
If you’re one of these people living in a rich country with low fertility rates, consider taking some steps to reduce global wealth inequality. The easiest thing you can do is donate to some of the charities doing great work on this front. Two I’d highly recommend are:
GiveWell — these guys are obsessed with studying the effectiveness of their grants, which is awesome if you don’t have hundreds of hours to do your own research. They support a variety of programs, predominantly in Sub-Saharan Africa, such as medicine and bed nets to prevent malaria, vitamin supplements, and deworming — programs that are very cheap from a rich-world perspective but nonetheless make a huge impact on the lives of those affected.
GiveDirectly — leverages the fact that a relatively trivial sum of money in the rich world can be an absolutely life-changing amount in poorer countries. The program essentially consists of giving a lump-sum payment to everyone in a small village (again often in Sub-Saharan Africa) and then studying the effects afterwards. Very consistently, they’ve found that these payments allow people to invest in themselves and their children, improving their future economic and health outcomes considerably.
I’m sort of disappointed that Avengers: Endgame didn’t end with everyone, after defeating Thanos and undoing the snap, getting together to research and fund the eradication of global poverty. It seems we’re going to have to write that ending ourselves.
I actually learned while writing this that OG comics Thanos had nothing to do with population control — apparently he wanted to kill half of all people because he had a crush on, like the physical embodiment of death. So while I’m cross with MCU writers for lending some credibility to Malthusian ideas, I… can definitely understand why they decided to alter that plot point.