Cavemen had to work together for common goal (survival) hence people usually root for each other. In modern world, people compete and try to one-up each other. No common goals. Big difference.
> Cavemen had to work together for common goal (survival) hence people usually root for each other.
How is that any different today? People manifest survival in a totally different way today, and the human being either choses to use other people to survive (bartering) or survive on our own (live off the land).
Survival is already an non-issue for most people in modern society and non-3rd world countries. Most friendships and relationships today are built on things that are so fragile, vulnerable, and superficial.. it's not even close.
If survival was an issue (fighting aliens for instance), we'd all be united in a way that would be unrecognizable today.