You're a team player; nothing great has ever been accomplished with just one person. Anyone who says otherwise is probably a not very nice person, and not someone who you feel the need to be associated with. You make friends for life, and you take those relationships very seriously. Like, blood oath seriously.
There is nothing that has been invented that we cannot live without. Because, for something to be invented we've had to not have had it before. People sure would piss and moan though if the car was taken away....to answer your question.
Well since it seems to be established that people can live with one lung, what else can't they live without? People can live with one lung, one kidney, barely anything for a stomach, a few feet less of intestine, no appendix, no tonsils, half a brain.