The reason people work together is fundamentally the same reason you go to work - self interest. You're rarely there because you genuinely believe in the mission or product - mostly you just want to get paid and then go do your own thing. And that's basically the gears of society in a nutshell. But you need the intelligence to understand the bigger picture of things.
For instance Chimps have intricate little societies that at their peak have reached upwards of 200 chimps. They even wage war over them and in efforts to expand them or control their territory. This [1] war was something that revolutionized our understanding of primates behaviors, which had been excessively idealized beforehand. But they lack the intelligence to understand how to bring their little societies up in scale.
They understand full well how to kill the other tribe and "integrate" their females, but they never think to e.g. enslave the males, let alone higher order forms of expansion with vassalage, negotiated treaties, and so on. All of which over time trend towards where we are today, where it turns out giving somebody a little slice of your pie and letting him otherwise roam free is way more effective than just trying to dominate him.
Citation needed on that one.
> Consider that Sparta and Athens were separated by only 130 miles, yet couldn't possibly have been further apart!
They spoke the same language, shared the same literature, practiced the same religion, had a long history of diplomatic ties. When the Persians razed Athens, they took refuge with the Spartans.
> For instance Chimps have intricate little societies that at their peak have reached upwards of 200 chimps.
Again, I don't think this claim stands to evidence. The so called chimp war you mention is about a group of about a dozen and a huge fight that broke out among them. That doesn't support the idea that they are capable of 200-strong 'intricate' groupings.
"They spoke the same language" ... not exactly, the Spartans spoke Doric, while the Athenians Attic. (Interestingly, there is a few Doric speakers left [0].) While those languages were related, their mutual intelligibility was limited. Instead of "Greek" as a single language, you need to treat it as a family of languages, like "Slavic".
"shared the same literature" ... famously, the Spartans weren't much into culture and art, and they left barely any written records of their own. Even the contemporaries commented on just how boring Sparta was in all regards.
If we delve deeper into ideas about how a good citizen looked like, or how law worked, the differences between Sparta and Athens are significant, if not outright massive.
While those two cities weren't entirely alien to each other, had some ties, same gods, and occassionally fought on the same side in a big war, there was indeed a huge political and cultural distance between them. I would compare it to Poland vs. Russia.
Put another way, you're arguing against an example and not a fundamental premise. Proving the example is correct doesn't really get us anywhere since presumably you disagree with the fundamental premise.
I'd much rather focus on "prepping" by building social resiliency, instead. The local community I'm plugged into is much stronger together than anything I could possibly build individually.
