So, hello and everything.
My question, which I haven’t found on this site, which I do enjoy, is: What is the origin of nonverbal gestures? Specifically handshakes, the thumbs up, smiling, and laughing. Ostensibly, these gestures seem aggressive. Gorillas think eye contact is threatening, or so I am told. So How did grabbing someones hand, bearing one’s teeth and barking at them become signs of trust?
For the record, yes, I have read Eric Idle’s The Road to Mars
Smiling and laughing are, I believe, instinctive - we do them because we’re hardwired to, and we react to them in certain ways because we know that people do them involuntarily. Handshaking is a cultural thing, but for most mammals, non-violent physical contact is an expression of trust - like a cat sitting on you lap.
The thumbs-up thing is just modern colloquial sign language. Most people throughout history wouldn’t understand what it means.
I’ve heard that the origin of the handshake is that it was a way of demonstrating that neither person had a weapon in their dominant hand (assuming that everyone involved is right-handed, of course). This might just be folk etymology, though.