Interesting document there Calm, if you can get past the unfamiliar jargon and the dry-as-dust academic style, but it doesn't answer the original question about why yawning is contagious. It concludes only that it's some sort of imitative behaviour unique to humans, which amounts to no more than acknowledging that it happens.
Odd, that, I distinctly remember seeing film of a baboon troop doing it too, and it clearly started as a threat display by the dominant male. I also clearly remember reading about researchers dealing with chimps and gorillas having to be very careful about smiling, because a display of teeth, even crummy little ones like we have, they often interpret as a threatening gesture.
Ah, maybe my memory is fooling me. It's done that before. But we're still back where we started: nobody knows.
Odd, that, I distinctly remember seeing film of a baboon troop doing it too, and it clearly started as a threat display by the dominant male. I also clearly remember reading about researchers dealing with chimps and gorillas having to be very careful about smiling, because a display of teeth, even crummy little ones like we have, they often interpret as a threatening gesture.
Ah, maybe my memory is fooling me. It's done that before. But we're still back where we started: nobody knows.