It’s immoral because familial love lacks a sexual desire, which is probably a genetic program to prevent the deformities and abnormally caused by narrow gene pools. It’s programmed into us as gross, or damaging as mechanism to protect the species, as well as individuals. The disgust reflex is to protect us from threat to health. This person asked you this question because his/her assumption is that Atheists are immoral. Basically, ask her whether it's delicious or healthy to eat shit. Because that is the kind of question they are posing you, and it’s fucking stupid. Of course there is a phenomenon where siblings separated at a young age meet by chance later in life and fall in love and have a sexual attraction. That is understandable and I think very psychologically difficult.

“Morals” are often simply social mores that have developed because they benefit the tribe. Incest was harmful to the tribe based on issues related to kinship and gene strength, So in that sense incest is culturally taboo, which is the linguistic equivalent of “immoral.” Limiting the question to “safe sex” does nothing to alter the morality because individual instances do not affect sweeping social perspectives. To test this, ask yourself whether you would mind reading about your activity in a certain domain in the newspaper. If you would, then that activity is culturally taboo or “immoral.”

In and of itself, incest is not per se immoral, although a controversial area and as mentioned there are very valid reasons why we have instinctive and social taboos against that in most circumstances.

A good treatment of some these issues turns up in the novels of Robert Heinlein, such as "Stranger in a Strange Land" and "Time Enough for Love".

What is always a problem in any relationship, especially a sexual one, is any large power imbalance and any lack of consent or incapacity of one party to validly give consent. Then it's abusive, and in many cases incestual relationships would also cross that line; but that is where the immorality stems from, and it is exactly the same issue as for example a teacher forming a sexual relationship with a current student of theirs, even if above the local age of consent.

One of the things that seems to be dramatically changing in recent decades is how we approach relationships and how we think about morality around that. A huge change in living memory is the development of reliable contraception, which I believe has demonstrably resulted in a massive drop in infanticide and child abandonment compared to past centuries, and also (for the most part) effective and safe treatments for most STDs which again is a game-changer.

The other perhaps less visible change that I believe is equally seismic in the social changes happening is ever-increasing typical lifespans for humans, which has massive implications for our patterns of relationships.

It's irresponsible on the genetic level, because knowingly creating a life that is very likely to have all kinds of recessive defects expressed is not a good thing. Unless you can be tested and have all the genetic drawbacks ruled out.

On an emotional level, it's a breakdown of the normal dynamics of the brother-sister relationship. Usually there's a lot of unspoken or even only unconsciously known power dynamics (among others) in that relationship, and adding that intimate wrench to the gears is likely to cause some larger issues. If you break up with an unrelated BF/GF, they can leave and that's the end of the story. If the BF/GF relationship with a sibling goes wrong, family reunions will never be the same, and you can't easily just cut that person out of your life.

I would say it is immoral largely on the grounds that incest is almost certainly exploitive. Our genes are not driven to reproduce with people that are too genetically similar. When close members are having sex I would immediately infer that at least one of them is exploiting the power dynamic within the .

It was certainly the way the Ancient Egyptian royal families kept their bloodlines pure as they believed that they were descendants of the gods. See the work of Frank Ruhli et.al - American Journal of Physical Anthropology 157(3) · April 2015 

Cain and Abel can best answer the moral aspect, other than that, to my way of thinking, adult, consenting sex should be shared freely among people...if you are going to believe in a god, then accept it as a gift...

I think it is immoral if it is parents and children, but not between two siblings if they are adult and consenting. I wouldn't do it, but I think it is okay between brother and sister and it started in adulthood and both are of similar age. When power dynamics are involved, it gets weird and wrong. So there have to be caveats.

I voted “immoral.” In the rare instance of adult, consenting adult siblings engaging in sex, I don’t have an issue and it is not necessarily immoral. This scenario is more likely and why I voted “immoral.” If either or both cannot consent (age, capacity) or an unbalanced power dynamic, then it is immoral. But I’m left with why in the heck would siblings want to engage in sex?

Don't. Fricken Hanoverians should be enough of an example. Safe sex? No, you mean safer sex. It's similar to the term "less than lethal" in law enforcement.

Start out with the fact that I am assuming that we are dealing with adults and not minors. Next consider that incest is a secular taboo that religious people hold, not the other way around. In two separate instances in the bible incest would be needed to repopulate. (Adam/Eve and Noah/Wife/Sons) As for immorality:

1. There is no 100% safe sex, and any child conceived could suffer defects as a result.
2. Sex complicates things, you can lose a good friend you have had sex with, siblings are more so.
3. The Westermarck effect plays a role, sex in this setting would be prone to power differences.
4. The social taboo would be unavoidable, a long term relationship would be either built on lies or ridiculed be most people you would meet.

This does get interesting with step siblings, I know of a case where two teens were dating and then became step siblings later on. They tried to keep dating after but it failed. There are some cases where siblings have found out they were related after they had already had sex, I assume they were in need of therapy.

In the end, the morality would be highly situational, but I would say the taboo serves us well.

I'm pretty sure that in some cultures it's not only moral, it's standard practice. As with any inbreeding, offspring are more likely to have genetic defects than when sire and dame are from different lineage, so the only issue I CAN see would be if children result from the sex. But morality is very subjective, and often stems from religious beliefs (whether we are aware they've been beaten into us or not)...

Not going by any religious beliefs it does not seem natural!

I'm astonished there is any question here?!?!?! yikes

We find it gross because we have evolved that sentiment to prevent chromosome damage. Same reason we feel sick when we smell rotten meat. Our instincts are telling us it's not good for us.

I don't think it's a moral issue and I don't care if cousins or siblings do it as long as they are safe. Same reason I don't care whether people drink or do drugs, unless they are pregnant. What you do with your life is nobody's business but yours; as long as you don't hurt people, kids included.

Ok, so we're assuming consensual sex, obviously. Between adults. Like, all parties involved are adults, not most of them.

Even if the potential for reproduction is involved, the potential for irreperable damage to the species is negligable, right? With such a diverse gene pool, regardless of how screwed up some subsection of the population gets through inbreeding (see Blue People living in West Virginia mountains...), there is a larger genetic base to mitigate whatever irregularities arise from the inbreeding of various small groups. As long as everybody isn't doing it, right? Although perhaps that's where the whole biblical provision came from in the first place. Too many villages full of people with hip-displasia and the cognitive inability to do much of anything other than fuck their siblings.

I mean, they inbred the hell out of dogs. You like your dog, right!? It might be a fantastic idea to selectively inbreed people. Just remove the ones with non-desreable traits from the gene pool. Although I'm pretty sure any sort of selective breed in humans is considered Eugenics, and that's generally frowned upon these days... Nazis fucked it up for everybody.

So, if you remove procreation from the picture completely (as the OP did)... then sure, why not? What about this consideration: what will children who grow up in an environment where Mommy and Daddy are Brother & Sister going to develop as their paradigm for romantic relationships? Since its obviously acceptable to fuck your brother or sister in this environment ("Mom and Dad are such hypocrites! Grandma says they've been hooking up since they were OUR age, but they won't let us do it yet..." ) what's to stop the kids from banging?

Assuming they are of the same age & maturity level, is this any more immoral than the parents banging? They would probably think its normal... enough... Keep in mind that aforementioned kids are probably not genetically related (unless adopted from same parents) as they cannot have come from original Brother & Sister, since we have already ruled out the potential for procreation in this example.

Synopsis: A moral acceptance of incest would lead to incest to become socially acceptable and potentially integrated into mainstream culture... but as long as there is no potential for children to arise from the union, it is no more or less morally acceptable than banging someone who isn't related to you.

In other words, if we ever find out the world is going to end in less time than it takes to gestate full-term, it becomes perfectly acceptable to fuck your sister.

P.S.- I am an only child.

Because as long as it's consensual and safe, no harm is being done.

Sex is never safe, when brounderies are not respected! Hearing stories from my peers as an older person...it does not bode well in old age! It appears to eat away at their mental health!

If you want to lower the bar to just propagation of the species.... Inbreeding is not good for the long-term viability of the species. There are a host of issues that can result.

Incestuous relationships are more.common in certain areas of the world. We can't simply say "ew gross" because of our adversion to it. Genetically speaking everyone has offered why it's not a good idea as recrssive genes. However socially speakjbg there is no good reason why it is Immoral

I don't think there is anything unethical about it as long precautions not to have children are done. I think to have children with a relative is extremely selfish and unethical due to the high genetic problems risks. I really think that anyone who is in a incestual relationship should commit to being willing to have an abortion if that situation arises. Of course there are other measures to prevent childbirth , but if they don't work an abortion should be had.

There's no morality about it. Its just fucked up. It has so many genetic and medical downsides that I would never condone it. But i think 2 consenting adults should be able to do what ever they want as long as it doesnt harm others

There's no morality about it. Its just fucked up. It has so many genetic and medical downsides that I would never condone it. But i think 2 consenting adults should be able to do what ever they want as long as it doesnt harm others

It may be that we have several questions that apply and are being confused.

1. Is it a good idea for the individuals?, for example, when (if?) they move on to new partners they “divorce” . Will they have problems adjusting? They will have little if the support available to married couples.
2. Is it legal? Cultures wind up on many sides of this one.
3. Is it a good idea for society? Will it lead to clans, as happened in rural WV for instance?
4. Is it a good thing for the family? I would put in the slippery slope (gateway to father-daughter sex) in this item.
5. If they do have children who continue the “tradition” genetic defects will pop up.

Which of these apply to a definition of “moral”? And there may be many others.

There is a cultural taboo against incest not a religious taboo although in the bible belt of the USA marriage between first cousins seems to be common. The set up of most social animals makes incest uncommon. eg male hyenas will move to another group to mate. Some bird species eg swans mate for life so incest is unlikely.