in many primates, smiling is way to reduce tension.. its the 'first' signal of submission.

the bigger the smile, the more submissive an ape or chimp or monkey is.

in humans, there is the well known 'Sh*t-eating grin' that is flashed when some one screw up, and want to defect anger. -we aren't so far from most other apes in that way


my other obsession