Then how do you explain the monkey isolation experiments where the monkeys kept in isolation all go insane.  Of course, there might not be such thing as an INTP monkey, or the ability for a monkey to entertain itself by playing Nintendo, so their only form of mental stimulation at all is by interacting with other monkeys.  As for humans not liking each other, most animals are territorial and also have somewhat hardwired limits to maximum group size, so they're probably designed to be aggressive and kill each other when the limit is breached.