Originally Posted by onoma
In fact, the theory behind incest being a universal taboo is that there IS something in our nature that prevents it.
They think there is a sort of sexuality dampener which occurs when being raised together, rather than being related. Which is why when you often hear of consensual incest cases it is usually amongst those who had not been raised together. Long lost relatives and such. And why adopted or step siblings rarely get involved with each other despite the lack of biological impediment.
In my own family I was raised with cousins so the idea of marrying cousins, despite it being legal, totally squicks me out.