We are fundamentally a tribal species. Our entire evolutionary history—the thing that turned us into the species we are—revolves around our incredible ability to cooperate and share information. The basic unit of survival for our species is the tribe, not the individual. So at one very fundamental level, we must be around others to survive and thrive. We must subsume parts of ourselves that are unacceptable to the tribe so that we can be allowed to be one of its members. "Us" is more important than "I".
But at the exact same time, the tribe only wants and needs us if we can provide value, preferably unique value to it. So while we need to fit in to survive, we must also stand out in ways that the tribe finds valuable, explore where other tribespeople won't and bring back resources (physical, conceptual, etc.) that others can't.
The tension between these two opposing forces—to conform or to stand out—is, I think, one of the key pieces of being human.