Such shifts in the way we compose ourselves seem to me to relate to what we do when we make art. When those first cave dwellers grabbed the painting sticks and decorated the walls my guess is that the urge to do came not so much from a desire to express themselves as from a desire to get the attention of others. And to dissolve the boundaries between individuals - assuming they recognised such boundaries at all. Perhaps it was not so much getting others' attention as the group looking at itself through its daubings.
These days we seem to scream for such attention, or at least some aspects of modern art suggest the raised voice, the neediness of the group. I suppose we are all needy in varying degrees - but the less we need, perhaps the better.