I thought the general premise is that humans can't form social groups bigger than around ~200. Which scans for me personally, its a struggle to maintain so many relationships. At which point group dynamics break down and factions begin to form. We have mental tech to try to minimise these issues, like nationalism or identity politics. We back these through cultural expression like dress, language, writing, the printing press, radio or the internet today.

Personally I feel like the effects of counter-culture are understated in humanity because I think it might drive a lot of human behaviour and its a natural outcome when a grouping grows beyond people's ability to maintain it. Counter-culture also offers a solid explanation for human insanity such as anti-vax which imho makes much more sense couched as:

"I hate that guy and that guy is keen on getting vaccinated, so fuck vaccinations, they're awful".

I would imagine one could find similar outcomes as this study of chimps, in human groupings too, albeit such experimentation would be unethical. Which is why I imagine it will eventually become a reality show someday: Lets play 400 friends or 200 enemies! Day 4: lets reduce the available food by 50% and see what happens... etc, etc.