Is Cousin Marriage Incest?

If there were ever mixed news on the same-sex marriage front, there was yesterday: while North Carolina hasn’t legalized same-sex marriage, President Obama has come out in favor it.

While the most recent news stories are far from the only ones to have spawned the trend, comparing same-sex marriage to cousin marriage seems to be a common thing to do. Usually, the post is accompanied by commentary or leads to comments along the lines of “so marrying family members of the opposite sex and making mutated babies is cool, but marrying someone of the same sex isn’t?”

People have been linking to maps like this on social networking sites and post image memes like the one below.



The idea is that it is unfair that what is deemed “incest” is allowed by the state but that same-sex relationships are not allowed to be recognized in that same way. While many (including me) would agree with that sentiment, are there any social, scientific, or ethical reasons to oppose cousin marriage?

The social taboo against cousin marriage is a relatively new one. In the United States, the taboo seems to have originated in highly unscientific studies that relied to eugenicist ideas. Either way, in the Victorian era and before, Europeans and Americans married their cousins with impunity. In many other cultures worldwide, people marry their cousins without any issues; the practice is not considered bizarre, taboo, or disgusting — in other words, not incest, since that word is defined by social custom. Currently, opposition to and disgust towards cousin marriage seems to be based at least somewhat on classism (i.e. “hicks” and “hillbillies” do it) and xenophobia (i.e. those people do it).



Scientifically speaking, the risks of cousin marriage are related to any children that might be produced as a result of the union. As can be inferred by how common cousin marriage used to be in Europe and the United States and is still in other parts of the world, the children of cousins are not all doomed to be drooling inbreds. In fact, the increased risk of birth defects in the children of cousins is incredibly slight. Many states only allow cousin marriage if there is no possibility of the production of children anyway.

With the social prohibition on cousin marriage being as arbitrary as it is and the science against the idea of cousin marriage being harmful, the only issue that remains is the ethics of it. Subjectivity reigns here, to some extent. Personally, I side with my grandmother.

As I’ve mentioned before, I grew up Muslim. According to Islamic law as well as Indian and Pakistani custom, cousins are fair marriage game. Therefore, by the age of puberty, I was required to give up hugging my male cousins and going in front of them with my head uncovered. Regardless of the Islamic and Indian stance, however, I never was expected or encouraged to marry any of them, a legacy courtesy of my mother’s mother. She declined all offers of marriage for any of her daughters that came from her relatives, noting that filial ties could become strained or even severed due to marital discord between two married cousins. That reasoning, to me, makes the most sense of any argument against relatives becoming sexually and/or romantically involved: even if they have no children or those children face little risk, families should be a safe space, not one fraught with the sorts of tension that tend to originate in romantic and/or sexual connections.

A similar argument is used by the main character of Arrested Development when talking to his son about his attraction to his cousin, which included a fake wedding, the one depicted at the beginning of this post.

Such reasoning is, of course, quite relative.

Heina Dadabhoy

Heina Dadabhoy [hee-na dad-uh-boy] spent her childhood as a practicing Muslim who never in her right mind would have believed that she would grow up to be an atheist feminist secular humanist, or, in other words, a Skepchick. She has been an active participant in atheist organizations and events in and around Orange County, CA since 2007. She is currently writing A Skeptic's Guide to Islam. You can follow her on Facebook, Twitter, or Google+.

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  1. Yeah. The main thing people freak over is malformed babies. The problem is, “Its complex”. Even brother/sister isn’t a 100% problem, since there is no certainty that either of them inherit the bod copy of a gene, that both parents have such bad copies, or that the bad copy is expressed in the child. If you assume both of them carry a gene, its 50:50 that they pass it on, and like 25% that they “both” do, and pass it on. If only one of them has it, then the odds might be better than picking someone at random. Its only a problem if a lot of kids result, so the odds go up, and those kids mix their genes too. Cousins, especially first cousins, are one step removed from that, so their odds of both having the same genetic glitch, is no worse than the general population, in most cases. Again, it only becomes a problem if you are dealing with something like old world “royals”, where, over dozens of generations, those bad traits keep being stuffed back into the system via such marriages.

    In general, its way over blown, and statistically not much worse than accidentally falling for someone that, by chance, happens to share a few of the same genetic problems you have in your family history. And, ironically, you probably won’t have much of a clue about what those are, with someone you are not related to. But, due to the crazies in the Eugenics movement, who didn’t know a damn thing about genetics or probabilities of trait transfer, and just plain paranoia about the odd problems that popped up in certain old families… And, the irony was, the movement would have committed the same errors themselves, by trying to “breed for traits”, while not understanding that those traits might be linked to the very things they didn’t want cousins, or direct siblings, passing on, in some cases. After all, if you don’t have a damn clue about genes, or what they do, its real easy to try for a superman, and end up with an idiot.

    1. I recall a genetics lecture about this subject and the professor said, summarized, that a single generation of incest has pretty low risk, but that incest can become damaging over multiple generations. So, feel free to fuck your sibling(s), but just don’t turn it into a family tradition.

  2. Excellent post. Genetically safe but also genetically like being in a relationship with Grandma, which seems a tad odd.

  3. I think most marriages shouldn’t even be same race, the mixing of cultural heritage and distinct genetics is a great thing. Too bad society’s freakish desire to racially classify people puts strain on mixed race kids.

    1. I feel compelled to point out that race is not a biological fact, but a social construction. There is plenty of genetic diversity within races.

  4. Aw yeah, my favorite topic.
    While I understand that most people find the thought of having sex with their relatives disturbing, I find it ridiculous that there are laws forbidding it. I mean, if it is between a child and a parent, it’s rape/child abuse anyway, and if the harmful cases are covered, why have a law that forbids ALL cases, even the non-harmful ones?
    I get that disabled children are more likely when siblings have sex, but then why is incest itself outlawed and not the conceiving of children in incestous relationships? And even that is imho not really right, since having children is a fundamental human right and we don’t forcibly sterilize people who have high chances of passing on genetic disorders to their offspring, either (or keep them from having children with someone who has the same genetic predisposition).
    Let me give you an example. In Germany we had some time ago a case where a woman and a man met, married and had three children without any disabilities. I don’t know how or why, but it was found that these people were siblings that had never known each other because they were adopted into different families (I think), and, well, long story short, they both have to go to jail and their children were taken from them.
    Tell me how that makes any sense at all.

    1. “we don’t forcibly sterilize people who have high chances of passing on genetic disorders to their offspring, either (or keep them from having children with someone who has the same genetic predisposition).”

      Actually, they did do this in the United States until pretty recently. The last person who was forcibly sterilized was sterilized in 1981, within the lifespan of many commenters here. If you are German you should know that the German government at one point took it much, much further, but this was basically inspired by the US eugenics program.

      1. I fail to see how the fact that this was done in the past and has been found to be immoral is important when all I was saying is that it isn’t normally held to be an option, at least in most secular countries. Also, of course I know what the Nazis did, but how is that relevant to a discussion of morals today?

        1. I’m trying to figure out how to say this without getting upset but what bothers me is the dismissal of experience + the idea that it’s totally in the past now and therefore not relevant. After the kinds of things I’ve had to hear and experience I don’t feel like it’s totally in the past or that I can be reasonably sure that those kinds of policies won’t be used again in my lifetime.

          I’m saying this as someone who was forcibly given drugs under the threat of violence with the explicit goal of making me more passive. Which, you know, people haven’t decided is immoral. I definitely still hear people advocating forced sterilization and there are definitely still many people alive who experienced forced sterilization directly. That it’s not considered legal right now in either of our countries doesn’t change that.

    2. 1. The couple knew they were siblings
      2. The woman “has a personality disorder” so was not held to be responsible
      3. 2 of their 4 children are disabled. 3 are in care.

      The problem is really not about who people have sex with, but who they have children with.
      I have read somewhere the industrial revolution and the mobility needed for it increased the average intelligence and the health of UK citizens just by enabling people to meet and marry people not from the same village.

  5. As a disabled person I always felt weird about the justification that is basically “well they might make more gross disabled people!” I mean I don’t necessarily think people should be trying to maximize the amount of disabled people possible, but it doesn’t exactly have a good impact on me if a disabled person being born is seen as innately terrible. If the response is “no they probably won’t have birth defects” that still is not going so great for me because basically it means I still have to be seen as defective, as an aberration from the “ideal” kind of person or body.

    Heina’s article didn’t really get into that, but I guess I wouldn’t have gotten into the culture/xenophobia issues even though I’m aware of them, just because those aren’t the issues that impact me directly.

  6. Cousin marriage may carry only a slight risk in a society where the practice is rare–they share only that one pair of grandparents, and other than that, the rest of his ancestors are unrelated to the rest of her ancestors. But what about a society where everyone has been marrying cousins for a long time, and your entire family tree is intertwined with your spouse’s? It’s good to marry outside the clan once in a while.

    1. Yes this is my thought exactly. The family trees must look like braids. How can that be healthy?

      Did the European royal family teach us NOTHING? :)

  7. Incest should be legal. The problem of reinforced recessive genes is simply a medical genetic incompatibility issue and those can happen between non related people too. If it’s an issue, get your embryos screened, or adopt.

  8. Great post Heina. I think that your grandmother had much wisdom and insight.

    In Oz cousin marriage is legal though uncommon (last I heard).

    In 1st year Uni I recall the probabilities were calculated out and the bottom line was, little increased danger wrt the general population. That was 40 years ago so the details are hazy.

    I do recall that just about everybody carries at least one copy of a harmful recessive allele.

    Here we are talking stuff like cystic fibrosis, alpha-1 antitrypsin deficiency, haemochromatosis and so on, each of which has an allele frequency of a few percent (some of them up to 10%) in Caucasian populations.

    However, I agree with @Kieron George that mixed race marriage is a good thing.

    As the song says, “What we need is a great big melting pot”

    And – it’s happening! I see it every day on the streets of my home town, the young international students together, and even in my own family – awesome stuff!

  9. Sorry about this, I ran out of time with the editing, but I was going to add:

    And it’s happening! (The melting pot that is)
    Every day I see it on the streets of my home town, the young international students together as I walk to work.

    Even in my own family! This gives me joy and hope for the future. Compared to 40 years ago, when we had the foul White Australia policy, we have come a long way.

    1. AI CTHULHU!!!
      ‘Ph’nglui mglw’nafh Cthulhu R’lyeh wgah’nagl fhtagn!!!

      (Editing fail – it was there but not visible initially)

  10. I’ll agree that blood family should be a safe space, where you can get away from romantic problems. That’s why I never dated any of my step-cousins. They’re family too. :) Plus my cousin growing up was more like a sister to me. :)

  11. Even if cousin marriage did significantly increase the risk of health problems for offspring, it still shouldn’t be illegal. I have plenty of health issues that will likely be passed on to my (hypothetical) children regardless of who I marry, and yet I’m still allowed to marry.

  12. Cousin marriage is legal in Norway. I can see no reason it shouldn’t be. (In fact, just reading the letter of the law it looks to me like you can marry your niece or nephew.)

    The legal history of restrictions on relatives marrying is an interesting one. Marriage to anyone closer than third cousins (originaly 6th cousins due to an error interpreting Roman consanguinity descriptions) was banned for centuries unless you got permission from the church, permission that cost money. In rural Norway, in the time of large families, a large fraction of the eligible partners could be that closely related to you, and the law was kept unchanged for a long while due to the economic interests of the church. It was then eased to a ban on first cousins marrying, still with the possibility of an official sanction if you paid.

  13. Disgust with mutually desired peer-wise relationships has always puzzled me. Whether it’s first cousins, second cousins, blood siblings, or adopted siblings — whose right is it to determine whether they can marry? What matters is whether the people involved will be happy or not.

    The aversion to incestuous relationships with a large age gap, like parent-child and uncle/aunt-niece/nephew, makes more sense. Though I don’t see the problem as the closeness of the relationship but as the large power imbalance between an adult and a child. In that sense, one should be equally wary of any relationship where one party is an adult and the other still a minor.

    Trying to control who has children with who has always been an exercise in eugenics. Remember that only a few decades ago it was illegal to marry a person of a different race. This was, of course, based purely on perception, since there is no “proper” or objective way to intelligently divide a group by race.

    There were similar attempts against the disabled, the mentally ill, and even just women deemed unfit to be mothers. Most of these involved forced sterilization, and it was sometimes done under anesthesia with the deception of treatment for another condition.

    None of this is particularly old news, so it’s surprising more people don’t know about it.

    1. My issue with these relationships is that I have a hard time believing that immediate family romances occur outside an imbalance of power. In theory, if you are 30 and want to sleep with your mom, whatever… but I can’t believe that most of these cases are people, glancing across the table at dinner one night and thinking my mom/brother/daughter is really hot, and I’d like to have a mutually respectful sexual encounter with him/her. I won’t say that it never happens, but I’m skeptical that’s the norm.

  14. Cousin marriage laws in many states differed; Connecticut, for instance, has a “second degree of consanguinity” rule, which basically means no 1st cousins. I am not aware of the rules in every other state, but I would bet Utah is pretty lenient.

    There is a bit of classism in the cousin-marriage thing, though I think that’s pretty recent, as more distant cousins married each other in the upper echelons not so long ago, and royal families — well, let’s just say that finding a member of the nobility in Europe who isn’t related to you at some level wold be well nigh impossible. TO put it another way, the family of the current Queen of England, the Tsars, and the German monarchs (Kaisers) were all relatively close cousins and the Hapsburgs married people off left and right for 600 years.

    Interesting point: in at least one culture I am aware of, getting interested in your mother-in-law is incest (the Yanomamo of South America). Your standing as a man is directly related to how you can flaunt the incest taboo. That is, if you can flaunt it, you must be a pretty powerful guy, and therefore marriage material. Also, they consider it incest to marry what we would call a female first cousin straight up, but again, violating this taboo is seen as a measure of power/prestige.

    I’d want to see a map of cousin marriages in the US like the one above. Be interesting…

  15. If memory serves, (I’m too lazy to make sure it actually does,) you’re more likely to have a child with problems if the mother gets pregnant while over the age of 35 than if you have a child with a first cousin. I don’t think either should be illegal.

  16. “Cousin Incest” is a problem among some immigrant populations in the UK, according to a number of stories and reports over the last few years, leading to a disproportionate number of birth defects and “mental incapacity.”

    I don’t know how much of the reporting is sensationalism and how much is viewing with alarm; but, if the quoted stats are being interpreted realistically it amounts to a “holy s%#t!” situation.

    Apparently it goes like this:

    1. As is historically common, waves of immigration lead to collections of said immigrants in the first few generations (understandable as they speak the same language, have similar cultural references, etc.) Think “Chinatown” or “Little Italy” neighborhoods in the US.

    2. Cousin marriage is common among Pakistani and Arab muslim cultures, as these are the members of the opposite sex it is socially acceptable to socialize with and therefore actually get to know.

    3. Due to the limited gene pool, two or three generations of inbreeding leads to a rapid increase of the frequency of detrimental mutations and double-recessives in the population.

  17. However that Wired Science link that Heina posted is somwhat dishonest in saying that the increase in risk is 3%, because the background risk is also 3% and that therefore represents a doubling (i.e 100% increase.)

    We need to be very clear in our minds and ask ourselves, % of what?

  18. When you consider that 99% of objection to gay marriage is based on religious bigotry, then even marrying your sister is OK, cuz the founder of the three main bigot religions married his sister and gawd was OK with that. And remember gawd & his son never said it was bad to marry your sister or cousins. But then again they never said it was wrong to marry same sex, just don’t go humping each other.
    Anyway kin marriage is not that bad as others have pointed out. The whole birthing monsters comes from repeated kin marriage thru the generations.

  19. As a side note, when living in the US, in poverty, under state medical aid, why is the mother offered a free sterialization but never the father?

  20. Everything was okay till you mentioned India in your article. Truth is that Indians never marry their cousins. That can’t even be imagined. That’s because cousins are treated as siblings in India. We had a culture of joint families in ancient India and all the kids growing up in the family were considered siblings. So marrying your cousin means marrying your sister which is unacceptable.

    I’ll advice you to do your research beforehand writing an article. You’re spreading misconceptions in the online society.

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