So interesting to read this ... I have had a similar view about the impact on temperature on culture and human behavior and productivity for decades and I have thought — at some point someone needs to explore this properly ... and now you have. I think there may be a book in here.
The approach -- talking about geography to understand human behavior -- reminds me Guns Germs and Steel by Jared Diamond which had a huge impact on me and others when it came out some twenty years ago.
Italy is a great example -- look at the culture difference between southern italy and northern italy. Radically different lifestyles and sensibilities.
And yes, air conditioning and the impact of air conditioning is a perfect way to test the thesis that temperature profoundly impacts human behavior and productivity.
I would argue that warmer climates have positive impacts as well -- there is a sense of connectedness and intimacy and shared delirium in warmer temperatures that may (?) cause people to feel more connected and reflective. I would argue that we are all different people at warm temperatures than we are at cool one. Note how large companies tend to turn the AC down to 68 and provide free coffee -- it results in a faster pace of activity. Meanwhile, warmer temperatures make humans more langorous and philosophical, perhaps. Think of southern literature in the US - Faulkner, Twain. Think of the magical realism of Gabriel Garcia Marquez. Then think of writers / thinkers associated with more northern US climates -- Ben Franklin (industrious), William James and all the scientists in northern regions.
The big take away for me is that we humans are animals who behave differently in different environments, and as you say we are inadequately aware of the degree to which context (including temperature) changes our behavior. We are quick to tell stories about ourselves that are self-congratulatory or defeatist without awareness of the subtle inputs to behavior change.
Love this and look forward to hearing about your further explorations of this idea. I will spend more time with it.
Ah, how geography impacts culture is one of my favorite topics, but so unexplored! The next topic I’ll tackle there is how they shape institutions and politics. Massive topic!
Hey Thomas, congratulations for a fascinating article! A couple of questions about the Nairobi/Lisbon comparison:
- Shouldn’t you compare temperature data from the 16th century, where Lisbon was indeed the capital of a global empire? Lisbon climate was likely colder back then, given the European Little Ice Age and discounting the impact of climate change in the recent years.
- Following that idea, do you think the increase of temperatures after the Little Ice Age could have contributed to the decline of Southern Europe in favor of the North?
- Even accepting the current comparison, couldn’t it be argued that Nairobi spends more time during the year above the optimal 22º temperature than Lisbon, making it potentially less productive? Lisbon does get warmer than Nairobi but only during summer, leaving the rest of the year to compensate. That'd also fit the popular observation in Southern Europe that everything slows down in summer!
1. The Little Ice Age probably didn't change that much. It was a fraction of a degree (like 0.25ºC) so I don't think it changes the argument
2. Northern Europe's growth precedes the Little Ice Age. In fact, it was during the Medieval Warm Period (eg Vikings). So that might have helped (but little). I think the biggest factor for Northern Europe's growth was technological, not climate. Specifically, the agricultural revolution (horse, horseshoe, horse collar, iron heavy plow) made northern populations explode where they could barely grow any grain before
3. Yeah but 15-26ºC all year long, without 100% humidity, is quite livable! This is not a bad temperature! Easy to work! Conversely, Lisbon's extremes make it harder.
1. Oh, I thought the Little Ice Age had a bigger effect, although if you add 0,5ºC from climate change the difference with the 16th century would be around 0,75ºC. But yes, I think the argument still holds.
2. I was thinking more of the warming making southern countries less productive, but 0,25ºC doesn't sound large enough to have such an impact.
Very cool and original. But, OK, that the pattern doesn't quite fit South and East Asia, i.e. 60% of the world population is a bit of an issue with this take.
Interesting article! I think Papua New Guinea might fit this theory - especially the balkanisation and conflict of people living in mountainous areas. I’m sceptical of the claim that ethnic diversity causes conflict, but note that Japan is famously homogeneous and seems to be quite wealthy and low on internal conflict. Obviously, there are plenty of examples where ethnic diversity does result in conflict.
Hi Thomas, thank you for the many insightful articles, that I have read this year already. I like this combination of economic history and geographic knowledge. Here I would like to add a little, but important note: As far as I have learned, the construct/idea of ‚race‘ was mostly promoted and used by politicians to support nationalism, based on weird ‚research’ done about 100 to 150 years ago, e.g. in my country, in Germany. As far as I know, modern scientists are saying today, that there is no evidence that supports the existence of ‚races‘. (E.g. real genetic differences are minimal, commonalities much bigger). I would thus remove this from the list of hypothesis, it has no foundation. ‚Culture‘ might work rather, that is an existing phenomenon, see system theory and sociological research.
Yeah I heard that debate. I haven't looked into it in detail, so take it with a grain of salt, but it appears that you can tell races apart phenotypically (observable) but also genetically.
Gist is: racial differences (~0.1% are just one order of magnitude different than the difference with our closest species (Chimps, 1-2% differences). If you get a DNA sample of a person, you can tell with 99%-99.9% accuracy what race they belong to. Of course, that doesn't mean we're complete strangers. In-group variability is higher than race-to-race average variability. Does that mean anything? I don't know yet. This might not matter for productivity, or for our topic at hand.
More importantly, it's such a toxic and delicate topic that I don't want to cover it without being fully informed on the topic, which I'm not. But I also think it would be dishonest to not mention this hypothesis.
Culture, of course, can be another factor, you're right. But then what causes that culture? Whereas genetics could be an ultimate cause (via evolutionary psychology), culture is more a proximate cause. An example of this is this article:
And one more thing, found it interesting how you prompted your question - so I tried it with a more open question in chat gpt (knowing that there is much that I don’t know). „Hi chat gpt, is the concept of ‚race‘ a scientifically founded concept?“ - „Great question — short answer: no, “race” is not a scientifically robust biological concept, but it has been and still is a powerful social concept. Let me unpack that a bit:
1. Biological perspective
• Genetics: Modern genetics has shown that human variation is continuous and does not fall into discrete “races.” The genetic differences within any so-called race are often greater than the differences between races.
• Population structure: There are clusters of genetic variation that reflect ancestry and migration patterns, but these don’t map neatly onto traditional racial categories (like “Black,” “White,” “Asian”).
• Consensus: The American Association of Physical Anthropologists and the Human Genome Project emphasize that “race” is not a valid way to classify humans biologically. Instead, scientists use terms like ancestry or population.
2. Historical & social perspective
• The idea of “race” emerged in the 17th–18th centuries in Europe, tied to colonialism and slavery. It was used to justify social hierarchies.
• Even though it’s not biologically valid, it has real effects because societies have structured privilege, discrimination, and identity around it.
3. Current use
• In medicine, researchers sometimes still use “race” as a proxy for risk factors, but this is increasingly criticized. Genetics, environment, and socioeconomic factors are more precise.
• In social sciences, “race” is studied as a social construct—something created and maintained by society rather than by nature.
👉 So: Race is not a scientific category in biology, but it is a powerful social reality with real consequences.“
The issue with prompting ChatGPT like this, and what it knows about you, is that it's very careful to be politically correct. I have systems prompts that try to eliminate all correctness as much as possible, and it's also why I use Grok, which is famously against PC. I'm pretty sure if you share that convo with me I can make ChatGPT bypass its PC-ness
Being open with critical thinking for wuestions in many directions is one strength in your reflections, thus I follow that alley - looking into such a hypothesis can even help to demystify wrong beliefs. Thus we agree it is a difficult terrain… looking at all factors/hypothesis will lead a way…
The way we frame a question already shapes the outcome.
By choosing indicators like per-capita income, crop yields, or mortality rates, the analysis locks itself into a particular worldview (that perhaps can be called modernist or reductionist) while sidelining other forms of richness (It's a bit like humans think humans are the most intelligent coz we define what intelligence is). Even leading economists (Stiglitz–Sen–Fitoussi, OECD) have shown that these indicators tell us little about actual human flourishing.
Temporality matters, let's don't flatten the history. We judge societies through today’s numbers, but modern urbanization (even the idea of nation-state) is only a few centuries old. Look instead at Egypt, Mesopotamia, or the Maya in their prime — all in hot or arid regions — and the neat story of geography falls apart.
And if we measured what has been lost — languages, ecological knowledge, indigenous ways of life — the conclusions would shift again. The same logic that celebrates “development, modernisation, or what need to be done to be wealthy ” also delivered mass extinction, cultural erasure, and looming planetary breakdown. That’s not a side effect; it’s baked into the categories we choose to explain why things are like that now.
Also, asking ChatGPT to validate the theory's uniqueness is a short circuit — LLMs tend to mirror assumptions in prompts rather than challenge them.
So the real problem isn’t the data points themselves, but the lack of reflection on the way we look at the world and explain things. Without that, any tidy theory risks reproducing the very mindset that got us here.
He's vastly better qualified to discuss this than me, but one thing I note is that your analysis is strongly focused on present GDP, and fails to mention the birthplace of civilisation in the hot areas of Egypt and Mesopotamia. Ancient Greece and Rome were also hot and without AC.
That doesn't mean your theory has no validity, but it's not the only factor.
The other issue is that GDP doesn't measure everything that matters. e.g. Siestas or relaxing in the shade with a drink with friends or family adds to the quality of life, and means you are then more refreshed and able to also enjoy the rest of the day more.
Tomas,
So interesting to read this ... I have had a similar view about the impact on temperature on culture and human behavior and productivity for decades and I have thought — at some point someone needs to explore this properly ... and now you have. I think there may be a book in here.
The approach -- talking about geography to understand human behavior -- reminds me Guns Germs and Steel by Jared Diamond which had a huge impact on me and others when it came out some twenty years ago.
Italy is a great example -- look at the culture difference between southern italy and northern italy. Radically different lifestyles and sensibilities.
And yes, air conditioning and the impact of air conditioning is a perfect way to test the thesis that temperature profoundly impacts human behavior and productivity.
I would argue that warmer climates have positive impacts as well -- there is a sense of connectedness and intimacy and shared delirium in warmer temperatures that may (?) cause people to feel more connected and reflective. I would argue that we are all different people at warm temperatures than we are at cool one. Note how large companies tend to turn the AC down to 68 and provide free coffee -- it results in a faster pace of activity. Meanwhile, warmer temperatures make humans more langorous and philosophical, perhaps. Think of southern literature in the US - Faulkner, Twain. Think of the magical realism of Gabriel Garcia Marquez. Then think of writers / thinkers associated with more northern US climates -- Ben Franklin (industrious), William James and all the scientists in northern regions.
The big take away for me is that we humans are animals who behave differently in different environments, and as you say we are inadequately aware of the degree to which context (including temperature) changes our behavior. We are quick to tell stories about ourselves that are self-congratulatory or defeatist without awareness of the subtle inputs to behavior change.
Love this and look forward to hearing about your further explorations of this idea. I will spend more time with it.
Ah, how geography impacts culture is one of my favorite topics, but so unexplored! The next topic I’ll tackle there is how they shape institutions and politics. Massive topic!
Hey Thomas, congratulations for a fascinating article! A couple of questions about the Nairobi/Lisbon comparison:
- Shouldn’t you compare temperature data from the 16th century, where Lisbon was indeed the capital of a global empire? Lisbon climate was likely colder back then, given the European Little Ice Age and discounting the impact of climate change in the recent years.
- Following that idea, do you think the increase of temperatures after the Little Ice Age could have contributed to the decline of Southern Europe in favor of the North?
- Even accepting the current comparison, couldn’t it be argued that Nairobi spends more time during the year above the optimal 22º temperature than Lisbon, making it potentially less productive? Lisbon does get warmer than Nairobi but only during summer, leaving the rest of the year to compensate. That'd also fit the popular observation in Southern Europe that everything slows down in summer!
Interesting points! Let me ponder:
1. The Little Ice Age probably didn't change that much. It was a fraction of a degree (like 0.25ºC) so I don't think it changes the argument
2. Northern Europe's growth precedes the Little Ice Age. In fact, it was during the Medieval Warm Period (eg Vikings). So that might have helped (but little). I think the biggest factor for Northern Europe's growth was technological, not climate. Specifically, the agricultural revolution (horse, horseshoe, horse collar, iron heavy plow) made northern populations explode where they could barely grow any grain before
3. Yeah but 15-26ºC all year long, without 100% humidity, is quite livable! This is not a bad temperature! Easy to work! Conversely, Lisbon's extremes make it harder.
1. Oh, I thought the Little Ice Age had a bigger effect, although if you add 0,5ºC from climate change the difference with the 16th century would be around 0,75ºC. But yes, I think the argument still holds.
2. I was thinking more of the warming making southern countries less productive, but 0,25ºC doesn't sound large enough to have such an impact.
Very cool and original. But, OK, that the pattern doesn't quite fit South and East Asia, i.e. 60% of the world population is a bit of an issue with this take.
Yes and no. The pattern that doesn’t work is that people don’t live on mountains, not that people aren’t poor. The area is super poor.
As per mountains, there aren’t that many livable mountain ranges.
Southern China does have them, and does have ppl living in them. Farther south they are too jungly.
I think the question is rather why not in the Himalayas and Tibet, and I think the answer to that is pretty obvious.
So I haven’t touched on it too much because the *mountain* aspect isn’t as present.
Impactful as usual. Great 👏👏👏👏
Interesting article! I think Papua New Guinea might fit this theory - especially the balkanisation and conflict of people living in mountainous areas. I’m sceptical of the claim that ethnic diversity causes conflict, but note that Japan is famously homogeneous and seems to be quite wealthy and low on internal conflict. Obviously, there are plenty of examples where ethnic diversity does result in conflict.
Ah good point!
What makes you hesitant to believe that ethnic diversity causes conflict?
It's bad, but what evidence suggests it is false?
Insane work as always man
Taiwan was also a colony of Portugal, albeit briefly – hence the still in-use name “Formosa”.
https://en.wikipedia.org/wiki/Spanish_Formosa
Keep up the good work!
I had forgotten about it! Of course, the OG. Thanks!
What causes culture? An important contribution to this discussion is the book by Henrich https://en.wikipedia.org/wiki/The_WEIRDest_People_in_the_World
I bought it. I need to read it! Thx for the reminder
Love this article! Soooo multidimensional! 🤩
Guyana is an interesting and recent outlier here. Whether it's sustainable is another question entirely.
I mean it has a shitty climate but OIL!
As does Houston, but AC.
Thought-provoking article. Thank you.
Fantastic article!!!
Hi Thomas, thank you for the many insightful articles, that I have read this year already. I like this combination of economic history and geographic knowledge. Here I would like to add a little, but important note: As far as I have learned, the construct/idea of ‚race‘ was mostly promoted and used by politicians to support nationalism, based on weird ‚research’ done about 100 to 150 years ago, e.g. in my country, in Germany. As far as I know, modern scientists are saying today, that there is no evidence that supports the existence of ‚races‘. (E.g. real genetic differences are minimal, commonalities much bigger). I would thus remove this from the list of hypothesis, it has no foundation. ‚Culture‘ might work rather, that is an existing phenomenon, see system theory and sociological research.
Yeah I heard that debate. I haven't looked into it in detail, so take it with a grain of salt, but it appears that you can tell races apart phenotypically (observable) but also genetically.
Here's what Grok has to say about this
https://x.com/i/grok/share/8H8UzVXLG7ZKKzgmGbvkxx9u7
And ChatGPT
https://chatgpt.com/share/68d51b2d-3cd0-8008-80c4-512c860568ad
Gist is: racial differences (~0.1% are just one order of magnitude different than the difference with our closest species (Chimps, 1-2% differences). If you get a DNA sample of a person, you can tell with 99%-99.9% accuracy what race they belong to. Of course, that doesn't mean we're complete strangers. In-group variability is higher than race-to-race average variability. Does that mean anything? I don't know yet. This might not matter for productivity, or for our topic at hand.
More importantly, it's such a toxic and delicate topic that I don't want to cover it without being fully informed on the topic, which I'm not. But I also think it would be dishonest to not mention this hypothesis.
Culture, of course, can be another factor, you're right. But then what causes that culture? Whereas genetics could be an ultimate cause (via evolutionary psychology), culture is more a proximate cause. An example of this is this article:
https://unchartedterritories.tomaspueyo.com/p/the-logic-of-myths
And one more thing, found it interesting how you prompted your question - so I tried it with a more open question in chat gpt (knowing that there is much that I don’t know). „Hi chat gpt, is the concept of ‚race‘ a scientifically founded concept?“ - „Great question — short answer: no, “race” is not a scientifically robust biological concept, but it has been and still is a powerful social concept. Let me unpack that a bit:
1. Biological perspective
• Genetics: Modern genetics has shown that human variation is continuous and does not fall into discrete “races.” The genetic differences within any so-called race are often greater than the differences between races.
• Population structure: There are clusters of genetic variation that reflect ancestry and migration patterns, but these don’t map neatly onto traditional racial categories (like “Black,” “White,” “Asian”).
• Consensus: The American Association of Physical Anthropologists and the Human Genome Project emphasize that “race” is not a valid way to classify humans biologically. Instead, scientists use terms like ancestry or population.
2. Historical & social perspective
• The idea of “race” emerged in the 17th–18th centuries in Europe, tied to colonialism and slavery. It was used to justify social hierarchies.
• Even though it’s not biologically valid, it has real effects because societies have structured privilege, discrimination, and identity around it.
3. Current use
• In medicine, researchers sometimes still use “race” as a proxy for risk factors, but this is increasingly criticized. Genetics, environment, and socioeconomic factors are more precise.
• In social sciences, “race” is studied as a social construct—something created and maintained by society rather than by nature.
👉 So: Race is not a scientific category in biology, but it is a powerful social reality with real consequences.“
The issue with prompting ChatGPT like this, and what it knows about you, is that it's very careful to be politically correct. I have systems prompts that try to eliminate all correctness as much as possible, and it's also why I use Grok, which is famously against PC. I'm pretty sure if you share that convo with me I can make ChatGPT bypass its PC-ness
Being open with critical thinking for wuestions in many directions is one strength in your reflections, thus I follow that alley - looking into such a hypothesis can even help to demystify wrong beliefs. Thus we agree it is a difficult terrain… looking at all factors/hypothesis will lead a way…
The way we frame a question already shapes the outcome.
By choosing indicators like per-capita income, crop yields, or mortality rates, the analysis locks itself into a particular worldview (that perhaps can be called modernist or reductionist) while sidelining other forms of richness (It's a bit like humans think humans are the most intelligent coz we define what intelligence is). Even leading economists (Stiglitz–Sen–Fitoussi, OECD) have shown that these indicators tell us little about actual human flourishing.
Temporality matters, let's don't flatten the history. We judge societies through today’s numbers, but modern urbanization (even the idea of nation-state) is only a few centuries old. Look instead at Egypt, Mesopotamia, or the Maya in their prime — all in hot or arid regions — and the neat story of geography falls apart.
And if we measured what has been lost — languages, ecological knowledge, indigenous ways of life — the conclusions would shift again. The same logic that celebrates “development, modernisation, or what need to be done to be wealthy ” also delivered mass extinction, cultural erasure, and looming planetary breakdown. That’s not a side effect; it’s baked into the categories we choose to explain why things are like that now.
Also, asking ChatGPT to validate the theory's uniqueness is a short circuit — LLMs tend to mirror assumptions in prompts rather than challenge them.
So the real problem isn’t the data points themselves, but the lack of reflection on the way we look at the world and explain things. Without that, any tidy theory risks reproducing the very mindset that got us here.
I recommend you read, "Guns, Germs & Steel".
I did.
AFAIK he doesn't talk about this
Maybe you should see what the author, Jared Diamond, thinks of your theories? Don't wait too long though — he's 88.
He's vastly better qualified to discuss this than me, but one thing I note is that your analysis is strongly focused on present GDP, and fails to mention the birthplace of civilisation in the hot areas of Egypt and Mesopotamia. Ancient Greece and Rome were also hot and without AC.
That doesn't mean your theory has no validity, but it's not the only factor.
The other issue is that GDP doesn't measure everything that matters. e.g. Siestas or relaxing in the shade with a drink with friends or family adds to the quality of life, and means you are then more refreshed and able to also enjoy the rest of the day more.
Very cool article. Or should I say “hot”.