How long can a human being survive without human contact before becoming insane?

A very good point Yazan and thanks indeed for your invitation ... I like your bright and disrespectful acumen, a sort of big rough diamond :) !

However, as far as I know, there is no relevant literature concerning experimental models of human 'relational deprivation'.

Well, maybe something similar have been tested by some world superpowers for military or spatial purposes or even in concentration camps during the 2nd World War, but clearly these outcomes are not relevant for the scopes of this discussion so I shall not take them into consideration.

So, philosophically (not psychologically) speaking, I could say that as socially oriented animals, humans cannot live a 'sane' life without interactions with other living creatures (no matter what you may like to consider).

Hope this helps (but would equally appreciate to read more about this :).