The question "why is incest illegal" is complicated, though the incest taboo is generally universal it's imposed differently in different societies. There is contradictory scientific evidence that inbreeding increases the risk for genetic disorders. No one study is definitive, and most do not take compounding — continued breeding within the same family line — into account.
"Incest" is the sexual relations between persons who are so closely related their marriage is illegal or forbidden by custom, or the statutory crime of sexual relations with such a near relative". Father-daughter and stepfather-daughter incest is the most commonly reported, but mother/stepmother-daughter/son incest is not uncommon.
There is research which suggests that forty percent of children who are sexually abused are abused by family members, and possibly 20 million Americans alone have been victims if incest. Incest as a from of child abuse is still one of the most under-reported crimes in the nation, and the world. It is still one of the least talked about, despite the media attention it has gotten over the last few years, the spread of internet forums where people often speak of their experiences anonymously, and celebrities who have spoken publicly of incest from their past.
There are a variety of Web sites available via search engines for questions on sexual abuse, or child abuse and incest. Should you feel you are being sexually abused, or know someone else who is, please consider reporting it to local authorities or social services or child protective services.
Rape Abuse and Incest National Network is a networking and information site.
Here you will find a list of International Resources on Domestic Violence — the broader term incest is often classified under.
Maybe it's because I am a male with no sisters and hence have nobody to look at me across the table with a wary eye come Thanksgiving dinner, but I don't understand why incest between adults is illegal. This whole Santorum mess has brought up the issue and I think that's good, kind of, in the way that it is good for a society to articulate clearly why it has the laws it has.
I'm not necessarily pro-incest. I don't think it should be encouraged by the state. I just don't understand why it is outlawed by the state. And I have yet to hear an intelligent argument against it. At Slate, William Saletan asks, if gay sex is private, why isn't incest?
Let's leave adultery and polygamy out of it for the moment. Let's set aside morality and stick to law. And let's grant that being attracted to a gender is more fundamental than being attracted to a family member. Santorum sees no reason why, if gay sex is too private to be banned, the same can't be said of incest. Can you give him a reason?
The easy answer–that incest causes birth defects–won't cut it. Birth defects could be prevented by extending to sibling marriage the rule that five states already apply to cousin marriage: You can do it if you furnish proof of infertility or are presumptively too old to procreate. If you're in one of those categories, why should the state prohibit you from marrying your sibling?
Imagine there is a brother and a sister. They are adults. Neither one is capable of having children. They want to jump each other's bones.
Why shouldn't they be allowed to
A) Get married, and/or
B) Have all the sex they want?
I'm not claiming that I am not reflexively creeped out by the thought of bro and sis getting it on (or bro and bro, or sis and sis). But I'm creeped out by a lot of legal behaviors. Being creeped out isn't a solid reason for a law, is it? If that's the case, we'll have to allow that possibly a majority of people are creeped out by the thought of gay buttfucking, so that should be illegal, too.