There is such a thing as a "Monkeysphere"...

...And they found it by looking at monkey brains. The bigger a colony, the bigger the brain of the monkey. They could take a monkey's brain, look at it, and say "This monkey belonged to a colony of 70 monkeys or so."
So one day, this smart alec takes a brain in, and the examiners estimated it to belong to a monkey of a troop of 200 or so monkeys.
Except it wasn't a monkey brain. It was a people brain.

Relevent? Certainly. Look at monkey colony dynamics.
Within of itself, it is a group of x creatures who live and hunt together, and are codependent. They will play with and love each other. They will suffer personally for the benefit of a fellow monkey.
These monkeys would die for one of these 70 monkeys.
And kill anyone of the remaining millions.
If someone outside of their colony, their Monkeysphere, steps within 50 feet of them
Why, they might kill them.

And don't pretend this has nothing to do with us.
We're pretty closely related to these guys, particularly on a behavioural level.
And evidence of the human Monkeysphere is everywhere.

As far as we go, "Monkeysphere" has been attributed in human behavioural psychology to describe everyone we care about. Apparently, 200-300 individuals, with possibilities for a lot more. Anyone you care about, who you would care about dying, rests within this monkeysphere.
And everyone else.... well, they're not people.

Remember that alien feeling you sometimes get when you see a teacher outside of school? Or when you catch that colleague of yours in town? It feels weird, because you're being reminded that these, these- animate objects, these things that are merely routine scenery, are actually people. Not just humans, people, with feelings, friends, family, thoughts, all of it.

And that's why it's so weird.

I think it's interesting to think about, that of all the thousands, possibly millions of faces you will see in your life time, you will only be affected by maybe several hundred of them. If that.

I guess you should pick carefully.