Incest, Happiness, and Other Unquestioned Assumptions

The topic of incest came up in my last post, and since I like tackling taboo subjects, let’s talk some more about that.

Is incest wrong?

I used to consider incest to be morally wrong, but the following passage in Jonah Lehrer’s excellent book, How We Decide, got me rethinking…

Consider this moral scenario, which was first invented by [psychologist Jonathan] Haidt. Julie and Mark are siblings vacationing together in the south of France. One night, after a lovely day spent exploring the local countryside, they share a delicious dinner and a few bottles of red wine. One thing leads to another and Julie and Mark decide to have sex. Although she’s on the pill, Mark uses a condom just in case. They enjoy themselves very much, but decide not to have sex again. The siblings promise to keep the one-night affair secret and discover, over time, that having sex has brought them even close together. Did Julie and Mark do something wrong?

If you’re like most people, your first reaction is that the brother and sister committed a grave sin. What they did was wrong. When Haidt asks people to explain their harsh moral judgements, the most common reasons given are the risk of having kids with genetic abnormalities and the possibility that sex will damage the sibling relationship. At this point, Haidt politely points out that Mark and Julie used two types of birth control and that having sex actually improved their relationship. But the facts of the case don’t matter. Even when their arguments are disproved, people still cling to the belief that having sex with one’s brother or sister is somehow immoral.

“What happens in the experiment,” Haidt says, “is [that] people give a reason [why the sex is wrong]. When that reason is stripped from them, they give another reason. When the new reason is stripped from them, they reach for another reason.” Eventually, of course, people run out of reasons: they’ve exhausted their list of moral justifications. The rational defense is forced to rest its case. That’s when people start saying things like “Because it’s just wrong to have sex with your sister” or “Because it’s disgusting, that’s why!” Haidt calls this state “moral dumbfounding.” People know something seems morally wrong–sibling sex is a terrible idea–but no one can rationally defend the verdict. According to Haidt, this simple story about sibling sex illuminates the two separate processes that are at work when we make moral decisions. The emotional brain generates the verdict. It determines what is wrong and what is right. In the case of Julie and Mark, it refuses to believe that having sex with a sibling is morally permissible, no matter how many forms of birth control are used. The rational brain, on the other hand, explains the verdict. It provides reasons, but those reasons come after the fact.

Then we have the following passage from Bill Bryson’s book, A Short History of Nearly Everything

If your two parents hadn’t bonded just when they did–possibly to the nanosecond–you wouldn’t be here. And if their parents hadn’t bonded in a precisely timely manner, you wouldn’t be here either. And if their parents hadn’t done likewise, and their parents before them, and so on, obviously and indefinitely, you wouldn’t be here.

Push backwards through time and these ancestral debts begin to add up. Go back just eight generations to about the time that Charles Darwin and Abraham Lincoln were born, and already there are over 250 people on whose timely couplings your existence depends. Continue further, to the time of Shakespeare and the Mayflower Pilgrims, and you have no fewer than 16,384 ancestors earnestly exchanging genetic material in a way that would, eventually and miraculously, result in you.

At twenty generations ago, the number of people procreating on your behalf has risen to 1,048,576. Five generations before that, and there are no fewer than 33,554,432 men and women on whose devoted couplings your existence depends. By thirty generations ago, your total number of forebears–remember, these aren’t cousins and aunts and other incidental relatives, but only parents and parents of parents in a line leading ineluctably to you–is over one billion (1,073,741,824, to be precise). If you go back sixty-four generations, to the time of the Romans, the number of people on whose cooperative efforts your eventual existence depends has risen to approximately 1,000,000,000,000,000,000, which is several thousand times the total number of people who have ever lived.

Clearly something has gone wrong with our math here. The answer, it may interest you to learn, is that your line is not pure. You couldn’t be here without a little incest–actually quite a lot of incest–albeit at a genetically discreet remove. With so many millions of ancestors in your background, there will have been many occasions when a relative from your mother’s side of the family procreated with some distant cousin from your father’s side of the ledger. In fact, if you are in a partnership now with someone from your own race and country, the chances are excellent that you are at some level related.

Now consider that in Ancient Egypt it was actually pretty weird if you didn’t marry a sibling, especially if you were royalty. The parents of King Tutankhamun, for example, were brother and sister 1, while Cleopatra married her younger brother Ptolemy 2. A little closer to modern times, we find that the current king of Thailand is the grandson of a brother and sister pairing 3 4.

So all this gets me thinking. I’m not saying you should go try your new pickup line on your sister or anything. I just wonder if the general repulsion we have towards incest is more due to cultural conditioning than it is to there being anything morally wrong with it.

Is happiness the best goal?

But incest isn’t the point. The point is that we all have beliefs that are so deeply ingrained that we don’t recognize them as beliefs at all. We just assume that’s how the world works, and so we have a hard time considering alternative viewpoints.

Another example along these lines is happiness as the primary goal of life. The following from Sebastian Marshall’s book, Ikigai

It’s hard to have this discussion with anyone from modern Western culture, because happiness-as-a-goal is so deeply ingrained that people don’t even realize it’s just a subjective call about what’s important. Actually, most people never critically examined happiness at all!

For me, I had a breaking out moment when I studied other cultures that had goals other than happiness. If you could talk to a 1600’s samurai and tried to discuss with him what’s important, he’d say loyalty, duty, and honor. If you said, “Wait, what about happiness? Isn’t that more important?”–well, he’d think you’re insane. He couldn’t express why–it was just a culturally inherited belief.

I remember chatting to an Indian chap in Mumbai a few months back. The conversation turned to his job at a call center, and I asked him if he enjoyed the work. In response, he threw me a crazy look like I had a blue florescent penis emerging from the back of my head. “I don’t have to do physical labor and I make enough money to take care of my family,” he said. “Whether I enjoy the work or not is irrelevant.”

For a privileged Westerner like me who thought a person would be mad to spend two thousand hours a year working a job they didn’t particularly enjoy, that conversation provided a swift kick in the perspective.

Weird, or just different?

Here’s a short and brilliant TED Talk from Derek Sivers, where he exposes several other assumptions many of us have about right and wrong…

Can’t see the video? Click here.

Question your beliefs

We’re all guilty of making assumptions about how the world works, about what’s right and what’s wrong. It’s hard to catch ourselves at it though. We don’t know what we don’t know.

But try this: Next time you find your worldview challenged, take a step back and question whether your beliefs are a reflection of reality, or simply the result of the time and environment you live in.

Promise I’ll try do the same.

  • See how I earned $4,190 online last month

    Subscribe below and get access to my monthly finance reports so you can see exactly how I make a living from my laptop. You'll also receive my latest articles direct to your inbox.

  • Share a Comment



    1. “Moral Dumbfounding” – I love it! I’ve been guilty of that state before, and I’m glad that if I ever get there again I can realize what it is and possibly how to fix it!

    2. Dude, I usually go against “the man” in every way I can… But You sir, take it to the extreme! Which, IMHO, is fantastic!

      Its mind-blowing how much culturally inherited beliefs we have…

      I will keep fighting, keep thinking man!


    3. It’s an interesting post and question.

      Something that came to me (and I think it’s a relevant point) is this:

      I grew up around a lot of conservative and homophobic people. One of their main arguments AGAINST same sex marriage was “what’s next? Legalizing sex with animals? Legalizing sex with your family members? Legalizing marriage between a man and multiple wives?”

      The pro-gay marriage people would always laugh and say “nonsense that’s crazy. That’s a red herring.”

      But maybe not? Maybe those repressed old right wingers had a point?

      • I don’t know, man. I’m pretty sure those “what’s next?” people were saying the same thing when slavery was abolished and women were given the right to vote. I think each issue should be given its own consideration.

        • I’ve always found it interesting that black males were granted the right to vote prior to white women. I wonder what the “what next” people must have thought about those politics…let alone the women of that period.

    4. I wonder what “wrong” or “right” mean to most people. I assume they mean, “Whatever I took for granted from an authority when I was young and have an emotional reaction about now.”

      I wonder how giving birth to a child that had genetic problems makes an act “wrong” as well. Say they didn’t use birth control, and she did get pregnant, and she decided to keep the baby and give birth to it, and the baby did have genetic problems (AFAIK that’s usually the result of incest with a parent, actually). How does that prove the sex was “wrong”? I mean obviously there is a result here that few people would like, but does that mean that something is wrong?

      What does wrong mean?

      • Well I think wrong is often subjective, but I also think having a child via sex with a sibling is irresponsible. You’d be knowingly bringing a deformed person into the world. The poor kid would likely have a tough life.

        • Continuing along the theme of what makes it wrong, we have to give pause to the reality that animals regularly have incestuous relationships that also result in offspring.

          As to deformities, I don’t think there is any scientific certainty, just a significantly increased probability, that offspring resulting from incestuous relationships will be deformed.

          Just for fun, take a look at this list of kissing cousins:

    5. I love you man, you know this. But I think screwing your sibling, who you shared the same womb with, when there are 3.5 billion other choices is verrrrrrrrry wrong, my friend.

      I know you had other points and the post is aiming for deeper than just that, but I am also disgusted by the fact that it’s legal to wed a cousin!

      • What if your sister was Kate Beckinsale?


        I’m not saying in this post that people shouldn’t be opposed to incest, just that one’s opposition to it doesn’t make it wrong. I want no part of gay sex, but if other people want to do it and they play it safe, then more power to them.

        • Hahaha then I would probably be VERY popular and have a lot more mates 😛

          Yeah I see where you’re going with it mate and I’m all about asking why we have such beliefs, and to see if they’re adopted or actually our own.

          Gay sex isn’t for me either, but two same-sex adults screwing, wouldn’t torture their parents (as they would also be brothers and sisters in this case). Well at least it shouldn’t!

          I’m probably never going to think about this the same way as you do, because I have a sister and the very thought of this turns my stomach.

          I reckon if you father two children who decide to “disrupt each others rabblement” you may feel different 😛

    6. Excellent, so – have sex with my sister then get a job in a call centre. Could have both of those done by the end of the day.
      Eternal happiness here I come!

    7. Surely the basis for the argument against incest is that children of close relatives are at significant risk of birth defects. Go back only a few generations, and it was imperative that your children were fit and healthy, your life and livelihood often depended on it. That’s what creates that moral argument, which is then embodied in folk tales in order to tell it in an acceptable way to children. At least that is true for western civilisation. Other cultures have other factors to consider.

      You can’t use historical royalty as an argument for incest, as they are not playing by the same rules as the rest of society, their decisions have more to do with inheritance and the transfer of, and acquisition of power. There are plenty of cases in history of royals marrying for power, money and influence rather than love, and often with disregard for how close a relation the partner was. If it curried favour between powers, it was fine to do. Queen Elizabeth and Prince Philip are 2nd and 3rd cousins by different lines of descent. Queen Elizabeth is even related to Barack Obama!

      Bryson’s point is a good one – statistically we have to be relatively closely related, but that small amount of genetic overlap is not significant in terms of genetic risk, and it can often be a good thing. Also, consider why there are ‘types’ of people in the world. You now, how you see familiar features in people, body types, eyes, jaw shape. There’s probably a bit of genetic inheritance going on there.

      As for whether you should consider incest, should the circumstances arise, that ultimately should fall to the individuals involved. As someone commented above, why consider it when the are several billion alternatives, you’d have to question the psychology of someone who might be confusing sibling love with an inability to form relationships with other people. But there are no doubt instances where siblings can enjoy complete and normal relationships, just like everyone else.

      • Great comment, Dave. Thanks for all that. Your last point especially makes a lot of sense.

        From what I’ve read, incest in Ancient Egypt wasn’t just limited to royalty. Apparently regular and poor people were at it, too.

        And yeah, I get the whole point about the risk of birth defects when children are born from incestuous relationships. I think people would have to be pretty irresponsible to procreate that way. But like Hiadt was saying, if birth control is used and the purpose of the sex isn’t to reproduce, then where’s the harm?

    8. I think the realization piece, which none of the comments are really talking about, is the video at the end. Moral relativism is incredibly important to keep in your perspective because it keeps your mind from becoming intolerant. The complexities of the world are so vast that any knowledge must be tempered, and the incest question certainly points that out. That isn’t to say we shouldn’t make moral decisions, we have to in every moment we live, but keeping a lightness and humility about our moral judgements is essential to maintaining our smile.

    9. A little upset I don’t have more attractive family members…haha. Awesome post Niall, that’s why traveling is so damn important. “Florescent blue penis…” good one. Props for stepping into such a racy topic.

      I got laid off two months ago and have spent all this time doing research and digging deep to really get to the foundation of my belief system. About work, about sex, about what it means to be a man, business, socializing, etc. Most of it I just inherited from my friends, my parents, and society. Nothing is more empowering and exciting than deciding what is true for our lives, using our own experience to make judgements and hold true to it. I feel like a completely different person than I did 2 months ago, and I’ve had multiple people comment on it. Be gone zombies.

      • Nice one, Alex. Sounds like you’re on quite the journey. Keep going!

        By the way, I thought you were going some place completely different when I started reading your second paragraph: “I got laid…”


    10. This post definitely gets me thinking. I see the word “incest” and it makes me cringe. I mean we’re not “supposed” to do that kind of stuff, right? We are taught from a very early age that it is unacceptable. It’s gross. It’s wrong. It’s repugnant. Incest is dirty old fathers having sex with their young daughters.

      So this post gets me thinking…. Sex between a brother and sister, why is it unacceptable? Why is it gross? Wrong? Repugnant?

      If people agree that consenting adults are allowed to have sex, then what makes a brother and sister any different, besides sharing parents? Why does sharing genetics make it so loathsome?

      I guess the reason it would creep me out with a brother and sister being sexual (or brother and brother or sister and sister for that matter) is because I feel a familial type of love toward my siblings and not a sexual/romantic and I find it hard to see how someone could have those types of feelings. However, that being said, I really can’t find a good reason as to what makes incest “wrong” between two consenting adults.

      I find this awfully interesting. Not the actual act of incest, but the reason behind it being so repulsive to others, including me and why we feel this way.

      Very thought-provoking post, Niall!

      • In the exact same way you won’t find a reason why it is wrong to do it with animals that volontarily participate. Seriously. Moral behavior is not always explainable (but of course everything can be questioned where and why it comes from). And as more godless the world gets, the more such behavior gets accepted. Nothing astonishing here as it seems.

      • Ah, I love when people post stuff like this in the comments, adding new food for thought. Thanks for that, Josh.

        That Wikipedia article also mentions Steven Pinker’s book, How The Mind Works. Been hearing a lot about that book lately. Must have a read of it soon.

    11. Do you have a sibling of the opposite sex Niall? I bet you don’t.

      If you did I doubt youd be supporting this outlook.

      • Nope, I sure don’t. And I probably would think a bit differently about this if I did.

        This post isn’t a support of incest though. I’m not saying that people should have sex with their family members. I’m just questioning why we believe it’s so wrong to do so.

    12. And btw, what about having sex with your parents then? or your grandparents? or grand daughters… all fair game so long as they are of age?

      • If both parties are willing, responsible adults and they use birth control, then yeah, I don’t see how it’s wrong no matter how they’re related.

        Again, incest isn’t something I’ve ever felt like trying myself, but just because it doesn’t appeal to me doesn’t make it wrong. In that regard, I view it much like homosexuality.

    13. Thanks Niall… in a world full of spoon fed bullshit all over tv, the internet, etc…. it’s refreshing to be faced with ideas that encourage me to actually challenge my own thoughts and especially why i think them……

      • Nice one, SamueL. In a world where people tend to run away from anything that challenges their beliefs, it’s refreshing to have folks like your good self reading and commenting on my blog 🙂

    14. I know this post isn’t about incest. But you pointed out a very small issue concerning incest… incest concerns rapes aswell, mis usage of children by parents or siblings. I know you know this. It almost sounds like you are looking for the most delicant subject to prove your point of view about keeping an open mind towards everything… yes Niall, question your beliefs.

      • Rape is a completely different topic, even if it sometimes involves incest. What I’m talking about above is two willing and responsible adults, who happen to be related, having sex with each other.

        Likewise, rape can sometimes happen between people of the same sex, but that doesn’t mean that homosexuality and rape are the same issue.

        • Yes..I know. In my language all sexual relations betweem siblings and parents-child are called incest. Again, I know this isn’t the point of your post.

    15. Dude..your numbers are crap.The no of people responsible for your birth:
      1st generation: 2 people (ur parents)
      2nd : 2(ur grand parents)+ 2 parents= 4
      3rd: 2(great great)+2(grand)+2(parents)= 6
      it is a simple arithmetic progression and not a geometric progression.
      After 64 generations, only 128 people would have been responsible for your birth and not some 100000….xxx…00 number u made up which is actually 2 to the power of 64 and not 2*64 as the case should be.
      The logic falls flat.
      Mail me in case I was wrong some where..

      • a) They’re not my numbers, and b) You’re wrong.

        You have four grandparents, not two. You have eight great-grandparents, not two. I haven’t checked Bill Bryson’s numbers all the way, but I’m willing to bet they’re a lot more accurate than yours.

        Thanks for reading though.

    16. I think the reason most people see it as wrong is bc we are taught that it is wrong. Plus before the 20th century contraceptives were not readily available to everyone so it was looked down upon bc of the deformities or mental problems a child could be born with.

      The other thing is that it kind of is a slippery slope. Ok, so the brother and sister were consenting adults, but if that incest is ok, then how about sex between a father and daughter (who is 18 – legal age of sex in US). If both are consenting would that be wrong?

      I could go both ways on that argument. You could say, “No, as long as the daughter is of age and consenting it should be ok” right?

      But a father can have an unfair influence over his daughter. After all, kids often try to please their parents. Could the father unfairly persuade his daughter through his words so that she has sex with him? And is that wrong considering he is not forcing his daughter to do anything she doesn’t want to do? This is where things get more complicated. Like is it unfair for the father who is older and has more knowledge to seduce his daughter who is young and more impressionable? He’s not raping her or forcing her to do anything she does not want to do, still is it ok? or is it wrong?

      And if you disagree with this case and think it is different from the brother and sister sex scenario I want to know why? What makes this different?

      • You’re right, it does get much more complicated that way. I haven’t thought much down that road.

        Makes me think of the Jonestown suicides. Jim Jones pretty much manipulated those people into taking their own lives, but you could also say that he never actually killed any of them.

        More food for thought. Thanks, dude.

    17. I know this article doesn’t say how many people left Africa way back when, but I believe it was 200-300.

      When you think that 200-300 people are responsible for populating the entire world outside of Africa, you KNOW there was incest. I admit when I first learned the number was so low I was shocked and a bit disgusted, ya know, because of the whole incest thing.

      When I was 9 I set out to read the entire Bible. I stopped after getting through most of Genesis, basically right around Genesis 19:30-38. (The story of Lot and his 2 daughters getting him drunk to have sex with him.) Really. I was 9 when I started to think, “you know, religion is pretty messed up.” The Catholic church could only claim me for a few more years after that.

      I also wonder about the fact that people are attracted to people how look similar to them. Not always, but very often. I read somewhere that it has something to do with our tribal past and being around people who look similar to you make you feel safe, like you know them, like they aren’t a dangerous intruder. Of course there must have been incest.

      When I was studying Middle Eastern history I learned it was, and still is, common to marry your cousin to keep the resources in the family (I’m sure there are many examples of this in other cultures as well). There are programs on the BBC today about girls being forcibly sent to the country of their family origins to marry their cousins to keep the wealth in the family. That sucks. I also looked up cousin marrying in the US several years ago and saw that it’s legal in half of the states for first cousins.

      Supposedly the Amish are more related to each other than other people because they live in a closed society (no one can convert). Siblings in those families often look like identical twins (of different ages). I think it goes something like this: almost all other people share 25% of their genes with their siblings but the Amish have been found to share 33%.

      Follow your nose! Haven’t there been a bunch of studies at least showing that women like the smell of men who have less similar genetic material than they do? The guy who probably had the highest chance of being (quite distantly) related to me (as in we both have a few ancestors living in the same city around the same time 150 years ago) smelled the least yummy to me of all my boyfriends.

      I’m a blue-eyed redhead. Recessive genes always remind me of ancient (and maybe not so ancient) inbreeding. The guy I was with who smelled the least good of all my boyfriends to me was also a redhead of a completely different shade than mine (my hair looked almost brown next to his brilliant copper). The jokes about 2 redheads together could be really tiring. No one ever cares nearly as much when 2 of any other hair color get together, even when the shade of the color is exactly the same. We didn’t share any other similaries in facial features (ie he was quite angly and pointy and I’m all round and baby-faced), though our skin was virtually the same color, and we both had blue eyes.

      Would you be surprised to know that redheaded guys often have a thing for redheaded girls? I am not. I see it all the time. There doesn’t seem to be as much interest from redheaded girls for the redheaded guys though. This reminds me of the study I read that showed males with blue eyes were the only type to show any preference for eye color in relationships. They preferred blue eyed females, and the explanation given was that it would somewhat reassure a guy that any offspring was his because of the combination of genes required to produce a blue eyed child. That made me wonder if the redhead thing was the same phenomenon occurring.

      These are just all my musings about incest over the years. So obviously people did it when they didn’t have much choice, and I bet you some of them enjoyed i 😛 I don’t think anyone should now, for reproduction anyway. I guess I don’t really care about siblings or cousins having consensual non-reproductive sex, but I do think other pairings are strange and gross (parents and kids or anything with a huge age difference makes me more uncomfortable about the power dynamic in the relationship). I know it’s legal to marry your cousin, but in this age of global online dating is it really necessary?

      It’s weird how our eyes seem to want one thing sometimes but our noses might tell us to look for something else.

      So glad I don’t have any brothers. So glad my hot second cousin has an accent that’s a total turn-off 😛

      I have 3 sisters, and there must have been enough genetic variety in there because we don’t look alike (well, I look vaguely similar to just one of them, and completely alien next to the other 2).

      Anyway, yery interesting post about how subjective morality is. Incest. Fascinating from all angles. Mixing up the gene pool is probably more fun, though.

      • Regarding follow your nose: some years back I read a book on the sex lives of insects (can’t remember the title), wherein was contained a footnote on this smell avoidance, a study had men run a treadmill and women would then sniff the armpits of the t-shirts worn by the men, to rate the attractiveness of the sweats smell. There was a midrange, geneticly speaking, neither too closely related nor too distantly related smelled best. A goldilocks zone if you will. The interesting(?) thing was, women on birth-control rated the sweat of those males who were genetically the closest to them as the best smelling.

    18. There is an important point to remember when discussing incest between siblings or family members living in the same home. The point would be that casting incest in a ‘normal’ light would make it even easier for certain family members to use power to engage in sexual abuse of other family members. It would make their crimes non-criminal. Most incest occurs between siblings when they are still minors and, therefore, there is a great chance that most of the encounters were not consensual. Sibling sex abuse is very common, much more so than parent abuse. As far as sexual relations among adult siblings, I have no point of reference for that. I would simply say that it seems like an individual choice, but one with inherent (pun) risks!

    19. Perhaps what is needed in this discussion is a contributor with some actual experience in the behavior in question. To make things less legally awkward, let me say that I know of a brother-sister relationship that was completely consensual, that started when both siblings were in high school, and was conducted without a single problem until they were accidentally discovered by their mother in bed together. The relationship began when he was 18 and she was 17, and was ended when he was 22 and she was 21. They “dated” in high school by arranging to help out another (unrelated) couple who were forbidden to date. The brother would take out the girl, the sister would be asked out by the guy, then they would meet somewhere and switch dates. The other couple apparently never realized that the siblings were doing this so that they (the sibs) could be together. In this fashion, they went to movies together, to the beach, to dances and to the prom, all without unduly alarming others. The sister used birth control, but she insisted that no condoms be used, because she felt that it ruined the intimacy of the moment. They were discussing how to move far enough away from family to begin living “married” (without an actual license, of course) and the possibility of having children using sperm from a sperm bank when they were accidentally discovered by their mother, which was very traumatic for everyone concerned. The mother was extremely upset and insisted that the relationship be immediately terminated. The drama upset the sister so much that she broke it off, but even with both of them trying to avoid seeing one another, they still “slipped” so many times (with tears later, and apologies, etc.) that the brother left town. While he was gone “on the road,” the sister married, and the relationship was over.
      But at Thanksgiving and Christmas and other family gatherings, sometimes there are some back-hallway kisses that say it won’t ever be over, not really.

    20. Great post! What I found interesting is that, while so many of us take years to get around to challenging assumptions in this way, little kids seem to do it naturally. My 5yo asked “why can’t you marry your sister or brother” and when I tried to explain about the concept of incest and it being a taboo and why that might be, he responded right away with “oh, so it would OK if both of you didn’t want to have any babies?”. Everything must be sooo much clearer before you take on board all that cultural baggage!

    21. I am very impressed that this blog is having a very intelligent conversation about the subject of incest. This is the sort of topic that get a person ostracized or worse! For me, I am of the opinion that the primary reason for incest being “wrong” is primarily because it brings unwanted “pregnancy” into a home that may not be able to afford care of another infant. Human nature also dictates that incest also creates an unhealthy preoccupation with sexual activity in younger and or more immature participants. This has been duly noted as being true verified by documented cases. Thus these issues would or could interfere with necessary activities. This could account for religious views backing it as taboo. Incest brings these problems every time with out exception so it is likely people tired of giving the reasons- then decided God condemns you to hell if you do it. That’s the quick take. People probably killed children they couldn’t afford to care for- which also increased God’s wrathful warnings. The Royal lineages are actually a far better reason to avoid incestuous unions! I also think the titillating nature of taboo sex will keep it a fascination for many forever probably. There are a number of good reasons not to engage in it and more than enough to secure the fact that worse rather than good or normal will be the most likely result and if this be the criteria for right or wrong- then incest would be wrong. This makes it a hot fantasy but a lousy reality.

    22. I believe concepts of morality are culturally transmitted, and that I am a product of the culture in which I was raised. I can reconsider and adjust my beliefs whenever I choose … and have done so in many things … but I think I’m safe in predicting that I will never overcome the icky feeling I get when I contemplate sex with a sibling. Moral or otherwise, I will not be indulging. To each his own, however.

      Thought-provoking, for sure.