Quote Originally Posted by mrdevious
I was watching a program on discovery channel, and this very subject came up actually. Apparently they've discovered that there are odours on a person's breath distinct to their direct family line. So when we kiss we're actually detecting that subtle smell, and if the smell turns out to be that of the same family that you're in, you're attraction to that person lessens, the experience being interpreted as a "bad kiss". So basically kissing is a safety mechanism to avoid inbreeding.
WOW. This explains so much.