Why is man considered as socio animal?

Question

We were asked to watch the movie of Jodie Foster "Nell" in our Anthropology class. It is somehow connected to my question.

Answer 1

We live in groups (as opposed to solo, or in mother-child temporary groupings until the young can survive on their own).

As far as "Nell" -- language, which is basic to us -- is a social thing. We need to be exposed to a language in our formative years to learn one; we use it to communicate with each other.

Answer 2

That would be because it's considered a social norm.

I have a nasty feeling that an awful lot of people use darwin's theories as a justification for this.