Wholeheartedly agree. In parts of society where our distorted ideas of "productivity" and "success" are absent, people share more freely. The island where my family is from comes to mind (Crete, Greece). There—in the rural areas—people were able to deal with the 2007-2008 crisis a lot more effectively than they did in the cities—esp. compared to Athens. What I observed is that if someone didn't have enough, the rest of the village would provide. There was a general understanding that that way the people with less would get back on their feet and help contribute to the overall pool.

Wonderful example!

I'd add that just looking at how families or circles of friends operate is also enlightening. The most cynical view is that these interactions are 'debt' based, but practically speaking that often isn't true either. I help my mother not because I calculate the effort she has invested in me or the value she brings me. I just do it because I love her and I don't need to think about how I've come to feel that way (which very well might be based on measurable behavior on her part).

IMO this has nothing at all to do with "distorted ideas of productivity and success" and everything to do with the rural vs urban lifestyle. There are plenty of similar examples like the one you gave that happen everyday here in the U.S. As a general human rule, smaller communities are more tightly knit and care more for each other.

That is definitely a factor. More complex social systems provide a degree of distance between you and the rest of the community (how can anyone keep up with having a sort of relationship with a few million others).

What is present in rural areas is a sort of respect and fear of exclusion (I think these two are reciprocal). But it is not impossible to have that on a local level in a large city. Having lived in both London and New York (similar population size, vastly different population density) I've seen this happen. In Manhattan specifically there is little respect for neighborhoods—comparatively—while in London residents care for their boroughs. Some direct actions that might have fostered that are simple things like community gardens/allotments which are very common in the UK.

that's my humble opinion, I'm not an expert in human social behavior.

but does this only work when the number of people in the tribe is low, and everyone has some social accountability to each other?

The problem of a free-rider is ever present, and in big cities, that problem is evident and thus you don't get the sort of community effort that you see in a small village.

Yeah - see “Dunbar’s Number”

Beyond Dunbar’s Number, it’s not clear that you can employ mutual-aid theories like tit-for-tat to restrain free-riding and cheating.

I think the truth is in the middle: there are many examples of secret processes throughout history and craftsmen jealously guarding processes except through apprenticeship programs where payment was years of cheap labor.

Oh yeah, it's not a binary thing. That said, in the case of craftsmen and their apprentices, I think the relationship was much less cold and transactional than, say, my startup friends who got a bunch of interns as cheap labor. At times perhaps, but not generally.