donnie_darko wrote:
My definition of incest would be having sexual relationships with someone who is at least as closely related genetically to you as a first cousin.
I am not aware of any society that prohibits sexual relations between first cousins, and societies that prohibit marriage between cousins are the exception to the rule China, Philippines, the Koreas, Taiwan, some US states, Croatia, Serbia and Bulgaria are the only jurisdictions I know that ban it, while the rules in Romania and India depend upon the religion of the parties. So, from that perspective, I believe that your rule is too broad.
But I also believe that your rule is too narrow, because it excludes legal relationships. A stepfather, for example, commits incest when he has sex with one of his stepchildren--even though there is not genetic relationship with them, whatsoever.
I see two public policy objections to incest: first is the increased risk of congenital disorders in offspring. (This is why double cousins and cousins related through identical twin parents should be considered separately from true first cousins). In practice, however, this risk can be managed--or at least mitigated--through
in utero genetic screening and prenatal evaluation.
The second is, to my way of thinking, much more important: the potential for abusive or exploitive relationships. People who live in close familial relationships with each other develop important levels of trust. There is significant potential for emotional damage if a sexual relationship between two members of the same family were to go wrong. You can break up with a spouse or a lover. But it's much harder to break up with your family.
_________________
--James