Smile, they say, and the world smiles with you. Unless you're wearing a mask. Then the world can't see your smile, much less smile back.

The rise of the protective face mask — first in China (where smog and SARS gave rise to its use years ago), then elsewhere in Asia, into Europe and now marching across North America — has abruptly excised half of the face from our moment-to-moment human interactions.

With it has come a removal of crucial visual cues that people have used for millennia to communicate, understand each other and negotiate space in the public arena — to find common ground.

A partial inventory of the information that's lost when the mask goes up: Smiles. Frowns. Lip movements. Crinkle lines at the mouth's edge. Cheek twitches that indicate approval or disapproval. Reflexive gestures that collaborate with the eyes to say: Hey, I mean no harm. Or: Hey — back off.

The face is the gateway to who we are, the front door to our humanity and individuality. We mouth off. We have face time (and FaceTime). We pay lip service and give each other lip. We grin and bear it. Are all these going by the wayside ... at least for now?

Which raises the question: If this endures for weeks and months, what would those analogues be? If half of the facial radio signal is obscured by face-mask static, how do the messages punch through? Will new methods of socially distanced nonverbal communication emerge?