There are two types of animal: those who are born and just go off already knowing all there is for their lives, and those that rely on a parent. The ones that typically grow up in a family unit are almost always going to seek a family unit to belong to later. Humans are no different.

We are a pack animal. It's as simple as that

Most mammals not all seem to have a symbolic relationship the young rely on the adults for protection and nourishment, even adults animals share meals and groom each other along with other privileges. We are just another member of the mammals.

Man used to live in small enlarged family groups like chimps or gorilla so its natural unlike our hugely populated cities.

It’s a fundamental you need to belong. We’re basically pack animals.

Here is a good source for looking: [documentaryheaven.com]

Can we say that interaction is an aspect of evolution?

But I don't have a clue on what that documentary would be.

I was never in a group in high school. I tried the local atheist group, it didn't work out, thanks to one male atheist. The workout group on FB for atheists wasn't helping me. The Admin told me I'm skinny because of my depression. That wasn't true. I don't belong in the "coterie of gossip" at work. I don't want to be. Cliches are not my thing. I'm in this group only. It's more of a community to me though.

Humans have evolved to be social animals. That is usually a positive thing, but it can be a problem on occasion.

LOL at first I thought you were talking about our need to belong to this group. I think i've found a couple of those already. But I promise I'll not reference those anymore.

Its because we are social animals. Cities, villages etc. are based on this principle. Everyone around you has been conditioned to be social and your very environment is predicate on this.