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Comment by bluGill | Hacker News Reader

You don't expand beyond the settlement - your fields are already there. You leave the settlement to tend the fields. You can't wall all the fields but you can wall the village.

expanding is done when the fields get too far to walk there and back in a day. Then you make a new village.

more likely you practice what birth control you can to limit population. Your other choice is go to war and kill some other village so your kids can move there. There was essentially no unclaimed land you could expand into.

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I agree. The main point here is that the inability to put the farm inside the walls provides necessary motivation to have people go out and get bit, which is what we need for the story to happen.

Walls themselves are a symptom. People generally build walls when they are afraid their village will be attacked. They are a lot of work so a safe village won't have them. (safe sometimes means you have a watchers and run to a nearby city with walls on need)

> You can't wall all the fields but you can wall the village.

An interesting take on this is depicted in Attack on Titan, where they do in fact wall all the fields - the city (I don't remember if it's like the last vestige of humanity or whatever) is surrounded in concentric ring walls, the outer one which contains villages and farmland having a circumference of about 3000 kilometers for an internal area of 723,822 km², making its area just a bit smaller than Zambia and Chile.

Of course, a 3000 kilometer, 50 meter tall wall is ridiculous. But then again the great wall of China is 21.000 kilometers long. I believe there's more info about the walls and their construction in the source.

Ballpark figures based on the ram earth construction for TGE vs AOT would have the AOT wall be 5-10x the volume & mass of the TGW. The issue is labor — the Great Wall probably represents 20–100 million ma years of labor. The AoT wall probably has at most 100k man years of labor it could've pulled from. That'd mean it's labor-mass ratio is off by 1000–10000x.

This gets into spoiler territory, but the walls in Attack on Titan weren't made with human labor. The first hint that something funky is going on was at the end of the first season finale, but we don't get the full story about the walls until much later.

It also was built when Marley was still very much a massive empire. So it wasn't limited to the manpower inside the walls. This is clear from how many of it's actual construction materials were used.

Enclosing a settlement gets easier as it gets larger. The amount of work is proportional to the perimeter, while the number of people to do the work is proportional to the area. The area is proportional to the square of the perimeter, so the work per person is inversely proportional to the length of the wall.

That only applies if you have the people. The limit of village population is the ability to grow enough food to feed it withing walking distance of the gate. And so your village cannot get a large enough population to overcome this.

Cities can only pull off a large population if there are a lot of villages growing surplus food (which is not what the village wants - in the medieval world cities were not making luxury goods farmers wanted so farmers would want to work less), and cities needed good bulk transport for all that food. Rome was a massive city in the day with just over a million people - today that is considered a tiny city and there are many much bigger.

Cutting off some forest might help.

What forest? Either it was owned by a noble with enough of an army to stop you, your great...grandparents already cut it, or the land wouldn't be useful for farming for some other reason.

North America had vast empty forests - but remember just before Europeans arrived disease (small pox) killed large portions of the population. We have very little recorded about what life was like before Columbus, but archeological evidence suggests that the land was already used to the max capacity of their technology. (Europe did bring technology to better use the land - for some definition of better. I'm not qualified to comment on why they didn't develop the technology, but there seems to be some interesting culture factors - perhaps you can find an expert)

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