> That works while the size of the community is ~100-200 people,

Yet we regularly observe that working with millions of people; we take care of our young, we organize, when we see that some action hurt our environment we tend to limit its use.

It's not obvious why some societies break down early and some go on working.

> Yet we regularly observe that working with millions of people; we take care of our young, we organize, when we see that some action hurt our environment we tend to limit its use.

That's more like human universals. These behaviors generally manifest to smaller or larger degree, depending on how secure people feel. But those are extremely local behaviors. And in fact, one of them is exactly the thing I'm talking about:

> we organize

We organize. We organize for many reasons, "general living" is the main one but we're mostly born into it today (few got the chance to be among the founding people of a new village, city or country). But the same patterns show up in every other organizations people create, from companies to charities, from political interests groups to rural housewives' circles -- groups that grow past ~100 people split up. Sometimes into independent groups, sometimes into levels of hierarchies. Observe how companies have regional HQs and departments and areas and teams; religious groups have circuits and congregations, etc. Independent organizations end up creating joint ventures and partnerships, or merge together (and immediately split into a more complex internal structure).

The key factor here is, IMO, for everyone in a given group to be in regular contact with everyone else. Humans are well evolved for living in such small groups - we come with built-in hardware and software to navigate complex interpersonal situations. Alignment around shared goals and implicit rules is natural at this scale. There's no space for cheaters and free-loaders to thrive, because everyone knows everyone else - including the cheater and their victims. However, once the group crosses this "we're all a big family, in it together" size, coordinating everyone becomes hard, and free-loaders proliferate. That's where explicit laws come into play.

This pattern repeats daily, in organizations people create even today.

I get the feeling it's the combination of Schelling points and surplus. If everyone else is being pro-social, i.e. there is a culture of it, and the people aren't so hard up that they can reasonably afford to do the same, then that's what happens, either by itself (Hofstadter's theory of superrationality) or via anything so much as light social pressure.

But if a significant fraction of the population is barely scraping by then they're not willing to be "good" if it means not making ends meet, and when other people see widespread defection, they start to feel like they're the only one holding up their end of the deal and then the whole thing collapses.

This is why the tendency for people to propose rent-seeking middlemen as a "solution" to the tragedy of the commons is such a diabolical scourge. It extracts the surplus that would allow things to work more efficiently in their absence.