Serena, my first bub didn't have colic, but it was AGES before I saw him smile. Maybe 3 months? He was a serious little chap. I was concerned too, with all my friends babies smiling early. Sometimes it's just their personality.

My second was pretty colicky to start off with, and he smiled pretty early - and is still a super cheery chap! Try not to worry - you might just have a solemn one? (To reassure you, I can hear #1 flicking a light switch on and off and giggling, so they still have their cheery moments!)

Shan, I'd heard that too. And I don't know. I think probably if they're making eye contact and smiling, then there's no doubt that it's a 'real' smile. But I don't know - I mean, kids aren't 'taught' to smile, so there's no reason why a baby can't have a genuine smile from birth, in my opinion.
(There are definitely poop smiles though, which are like a smiley grimace - hilarious. Look out for them one bub gets on solids down the track.)