alt Hacker News- Imagine you dug a hole 1 mile deep and 1 mile wide. How many humans do you think you could fit into it? The answer is about 60 billion, many times the current global population.
- If you dropped a human on a random spot on this planet, even if we just assume land, the median number of people within a mile would be exactly 0.
I think the second thought experiment is quite informative because it's easy to lose track of the reality when we mostly travel from packed city to packed city. But these cities, and the pathways that connect them, make up a negligible percent of the Earth. China is smaller than the US, and has pretty rough geography, yet was food self sufficient with a population upwards of a billion. They only became food dependent as their economy expanded and they replaced farms with iPhone factories, metaphorically speaking at least.
Finally, population growth in the longrun will always be determined by the groups with high fertility. It's never longrun stable unless everybody has the same fertility rate. So for instance the Amish today maintain a fertility rate of around 6. This is why there are now hundreds of thousands of them, and within a few decades they'll number in the millions. As highly educated, highly secular, high income individuals remove themselves from the gene pool, they'll simply be replaced by Amish. And as the former die off, and the latter grow - we'll eventually see population growth resume.
One last point. Fertility rates also determine age ratios within a society. Low fertility = most people are elderly, high fertility = most people are young. So it's not only economic collapse due to fewer people, but you create societies where there's a much greater social cost (due to elderly care), and far fewer people to take care of them. South Korea is a great example of this. If they don't fix their fertility rate, they'll collapse as a nation within the lifespan of some people alive today. 'Breaking News 2094 - North Korea successfully invades South Korea with one tank.'
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> And as the former die off, and the latter grow - we'll eventually see population growth resume.
Previously (centuries ago) most of the people were like the latter group. And things changed. I would not bet that a group can remain completely unchanged in the next tens to hundreds of years. There is of course a chance, but don't think it is as clear cut as you make it sound.
> Fertility rates also determine age ratios within a society
Plus immigration. Some like and accept that, some hate it and don't like it, we will see how it plays out, but there are more things involved than just fertility rates.
You can't even assume that Amish population growth will remain constant! See e.g. https://medium.com/migration-issues/how-long-until-were-all-.... We also don't know what will happen to Amish retention as the population grows, or what will happen if the population spreads into previously non-Amish areas -- it's just really hard to predict what's going to happen multiple decades in the future.