Anthropologists speculate that smiling actually derived from the mammalian instinct to bare their teeth when threatened.

Yes this is the new info I received after writing this article originally. I like the theory and think it has legs.

I totally agree with the opposites attract and have in fact just written an article that kind of covers this. However with humour I think it helps to have, if not an identical, but very similar humour to your partner of choice.

For instance I once went out with a girl and we watched a really crappy Kevin Spacey movie. At the end the child actor in it performs one of the hammiest death scenes I've ever seen in my life.

I was sitting on the floor at the feet of my partner, I looked up to share the joke and laugh about this guy's terrible acting, and a tear was rolling down her cheek.

She found the whole scene really moving and I just remember thinking to myself; this isn't going to work.

... it didn't

:-)

Cg