See also Dunbar's Number:

http://en.wikipedia.org/wiki/Dunbar%27s_number

Dunbar's number really can't be the whole explanation of man's inhumanity to man. Among primitive societies where people live as small bands in which everyone knows everyone, the murder rate is high. (According to /Guns, Germs and Steel/.) There's certainly lots of intracommunal violence and nastiness among most other ape bands too. And don't people in our society tend to be murdered by people they knew?

I don't think anyone is claiming that it's "the whole explanation". It's only an explanation for why people don't care about other people, which sometimes has violence and suffering as a side effect. In other cases, violence and suffering is purposeful, and this happens for other reasons.

> What do monkeys have to do with war, oppression, crime, racism and even e-mail spam? You'll see that all of the random ass-headed cruelty of the world will suddenly make perfect sense once we go Inside the Monkeysphere.

There's plenty of cruelty between acquaintances in the world, and a great deal of it is random and ass-headed. Lots of that cruelty falls under the headings of oppression, crime, and racism too. (War and spam are between strangers almost by definition.)

I forget what the research was called or who it was done by, but there's another magic number: 8.

Once a group/faction grows beyond that number, sub-factions within the group begin forming....

a good perspective on one of the aspects of game theory (or at least what I think is game theory):

Sub-systems will tend to maximize their gains even at the expense of the system as a whole...

Co-opetition is a good book on this subject

It's easily bridged, and I believe there's a degree of institutional pressure to not allow it.

In all of the following years of the war, artillery bombardments were ordered on Christmas Eve to ensure that there were no further lulls in the combat.

http://en.wikipedia.org/wiki/Christmas_truce