For the last several decades, the seemingly endless parade of new social media has been raising public awareness of boundaries — the psychological boundaries between human souls — and in the last few years we have begun to talk about this with a heightened sense of urgency.
About 10,000 years ago, the only important boundary between our openly living ancestors was a natural one — the skull that kept mental activity out of sensory range. What people were thinking and feeling was for them to know and others to find out. And the others did find out, because this sort of internal activity has a way of leaking into the face, hands, and body, and these things were still visible.
When our ancestors took refuge behind walls, of course, their bodies regularly disappeared for long periods of time. But privacy was tantamount to secrecy, and eavesdroppers pursued them through whatever cracks and knotholes the builders left behind. In doing so, whatever their original motive, they discovered vast perceptual riches — far beyond anything their ancestors had seen in the glow of a campfire — for insiders, thinking they were ...