I never thought the idea of a community would require such deep thinking...
The meaning of a community really depends on the community its self. I'm apart of the nerdfighter community, which means allowing my inner dork to come out and see the inner dork in others, it's a place where no one has to try to look "cool" because the whole point of this community is that we all have our "uncool" side. There is my community within my college and my major or nursing. This one means halving help in my learning experiences, and finding people with the same interests as me, and that I may potentially spend the rest of my life working with. Then there is my physical community of my neighborhood which to me means my history and people I've known all my life, and some I've known all their lives and that feeling of history and truly knowing a person. What all of three of these have in common is a feeling of connection and belonging. These communities are my roots and the people I can count on when I need them.
I don't think they are "necessary" but I do find them to be inevitable. Even if you're alone with no other humans I think you find yourself in a community. Jane Goodall was in a community of chimpanzees instead of humans. It's just as easy for the community to involve other species. THen there are many examples in pop culture (Jungle Book, Tarzan, Cast Away). In all of these, regardless of how realistic they were, include some form of community and dependence.
Once again a community isn't necessary for a happy life. We create our own communities based on what we enjoy. And although I can't think of the name for it right now, there have been plenty of people that were scared of leaving their own home whether it be from Germiphobia ( sp?) or another fear. However, these people were happier without that community and happier living on their own completely secluded.
Sorry if that is long winded, but I figured it would be better to give you too much information rather than not enough.
Community is something humans are just inclined to doing. We work together and accomplish things. I don't think people necessarily need community to be happy, but to have a more fulfilled life I guess. I mean, here we are a part of a community of nerds that have different interests and what not. I think since humans like to put things into categories and subsections, communities are just an inherit part of life whether it's based on interests or just geographical locations.