How do you know what life was like 2000 years ago? I don't think you can truly know when this convention appeared. I suspect it's tied to urbanism at least. If

How do you know what life was like 2000 years ago? I don't think you can truly know when this convention appeared. I suspect it's tied to urbanism at least. If you're living alone in the woods, miles from anywhere, and someone walks past your house, you're probably not going to politely ignore them.