Not everyone requires the same amount or same kind of social contact, but everyone requires social contact. Do you know how many things in your brain and body are devoted to absolutely nothing but socializing? It's a pretty large number. Let me give a very VERY cursory overview.

1. Language. You could think without language. It exists for no other reason than to transmit information from one brain to another. There are multiple areas associated with the formation, interpretation, and acquisition of language in your brain. And by that, I mean multiple for each one of those. And that's not even getting into non-primary languages.
2. Your face. You know how you have the ability to move your eyebrows? That serves no other purpose than expressing things to other people. All those muscles and reflexes devoted to facial expression are solely for the enjoyment of other humans (well, and sometimes pets, but they're for substitute proto-human companionship anyway).
3. Your entire body's unconscious reflexes like laughter, ticklishness, posture, gesticulation, and so on. Do you think it's a coincidence that people in a guarded mood more often have their arms crossed? It's not. That takes a good deal of infrastructure.
4. Sense calibrations. Humans have a horrible sense of smell compared to most other animals, and we can STILL smell mood and hormone signatures on each other unconsciously. You can pick human faces and shapes out of almost anything because of how incredibly fixed your brain is on human faces and shapes.

I'm missing a TON here, but the fact is, your body is better constructed to socialize than it is to do, well, pretty much anything a modern human does other than socialize (with the exception of people who chase down game with pointy sticks or harvest wild plants in the savanna), and your brain is often grabbing at straws just to find anything similar to it.

Can a person live without human contact? Yes. Will it take a toll on their psychology? Immensely.