What drives us to not only put our bacteria-filled mouths together, but to insert our tongues into each other’s face holes? Seriously, how did that even happen?
If you are an inquisitive human being with about six minutes to spare from your life, then watch the following video. It may not answer all your questions but at least it attempts to make some sense out of this bizarre social act that leads to mono.
Oh, and happy Valentine’s Day.
Source: brain pickings