[chockablock]

> Why not allow 12 year olds to marry as a consititutional right?

Children are not considered capable of consent.

> Why not allow brothers and sisters to marry?

Claimed societal interest in preventing harm to offspring born from inbreeding.

> I'm not trying to make a slippery slope argument. I'm really asking.

OK, well now you have a couple answers.

[slavik81]

>> Why not allow brothers and sisters to marry? > Claimed societal interest in preventing harm to offspring born from inbreeding.

If that's all, it seems that logically, brother-brother marriage should be OK.

I suspect the real reason for a lot of these laws are is "because it's icky". The justifications seem more like rationalisations.

[murbard2]

Yes, but "it's icky" didn't form arbitrarily, ex nihilo. If you go one level deeper and ask why it's considered icky, you may find justifications, some good, some bad, some outmoded, some relevant.

[hluska]

I should preface this by saying that Christmas dinner at the Hluska household is already complex enough...:)

On a serious note though, you allude to one of my favourite aspects of law. Throughout history, views on brother-sister marriage have changed. At points/places, it has been perfectly fine for brothers and sisters (especially in elite families) to get married.

I am far from an expert in this field so can't speak to why our norms changed. If you want to take this further, you should start with the Westermarck effect and look into the kibbutz study. Or, maybe consider how marriages between families evolved as a way of formalizing business or other strategic relationships. Either way, taboos are cool!!

For example, in ancient Greece, homosexuality was fine. Hell, even Zeus advocated it as a way to prevent pregnancy. Yet, by the early 1900s, it was considered mental illness through much of the world. Taboos are always in flux and I can't figure out why. Logically, you'd think that science and information sharing would make us all more liberal and taboo-proof, but I'm not sure that is happening.

- https://en.m.wikipedia.org/wiki/Westermarck_effect

[fizzbatter]

> Logically, you'd think that science and information sharing would make us all more liberal and taboo-proof, but I'm not sure that is happening.

I think you're right - but i also think you're underestimating the lack of science minded individuals in the ones who are less liberal (such as in the US).

Education is becoming a big problem, in general.

[JoeAltmaier]

The 'inbreeding' argument doesn't, and has never, held water. Not that I'm about to jump my sister; but as a point of science its not terribly significant. Cousins can actually have closer DNA than siblings; cousins are often allowed to marry (varies state by state). The idea that only horrible monsters will result is silly; its how all purebred farm animals are created.

[cyorir]

The main argument against incest that I know of pertains to recessive genetic diseases. Suppose one parent has a recessive disease, and the other does not (P generation). Then F1 generation may have carriers, but will not display the disease. If F1 mate together, however, then the F2 generation may contain individuals who are homozygous for the recessive allele, so they will display the disease.

There was a case in which this happened, the "Blue Fugates" [0], who had a particular recessive disease[1].

[0] https://en.wikipedia.org/wiki/Blue_Fugates [1] https://en.wikipedia.org/wiki/Methemoglobinemia

This argument made sense before genetic screening was available, but falls apart with genetic screening, since you could screen the siblings to see if they are both carriers.

[DanBC]

The other argument against incest is to protect vulnerable people from abusive adults.

There are enough cases to realise this is something of a problem, although protections can probably be built into the system.

[JoeAltmaier]

And other forms of marriage are not subject to abuse? Doesn't rise to the level of prohibition, I think.

[driverdan]

[citation needed]

[jrs235]

>Children are not considered capable of consent.

Children (minors and the "age of majority") and age of consent is defined by law. While we have come mostly to an agreement on the age of consent for many things, nothing prevents us from changing our definitions or age of consent for varying activities.

[spdustin]

The age at which the brain is capable of the higher levels of executive function necessary to make rational, informed decisions (not saying that such decisions are guaranteed, just that the brain is capable of considering them) is a function of biology, i.e. defined by natural law.

The legal framework of consenting age protects the abuse of a minor's inability to "think like a grown up", though it's arguable if the age of consent is too low (because biology dictates an older brain has a matured executive function capacity) or too high (because some kids, as many can attest, are wise beyond their years).

[jrs235]

>The legal framework of consenting age

Should be "Current western and developed/modern civilization's legal framework of consenting age"...

[dorgo]

>> Why not allow brothers and sisters to marry? >Claimed societal interest in preventing harm to offspring born from inbreeding. They can produce offspring without a marriage. Or, if it would be allowed, they could marry and dont produce offspring. Dont see how one is connected to the other. Its not a question of reasoning. All you need is a lobby big enough and enough time and you are allowed to do whatever you like to do. Marry a 12 year old, marry a pet, marry a car..

[ikeboy]

>Claimed societal interest in preventing harm to offspring born from inbreeding.

If that's a valid argument, why isn't the same argument [1] against gays valid? Conversely, if greater risk isn't enough of a constitutional reason to allow bans on gay marriage, why is it enough to make incest bans constitutional?

[1] http://www.cdc.gov/hiv/risk/gender/msm/facts/

[foldr]

How would legalizing gay marriage increase the risk of anyone getting HIV? You're not making any sense.

[ikeboy]

The same way that legalizing brother-sister marriage increases risk. Or could you explain more fully why one would increase risk but not the other?

[foldr]

You think that gay men are more likely to have unprotected sex with multiple partners if they get married than if they don't?

[ikeboy]

They might; something being officially sanctioned might increase the frequency.

Can you at least see a reasonable comparison between the two? If you don't think changing marriage laws affects behavior, shouldn't that apply to incest as well?

It seems to me that "legalizing gay marriage won't increase gay sex overall" and "legalizing sibling marriage won't increase sibling sex overall" are likely to be inconsistent with each other, and that the first is implied by your wording; if gay sex increases, it should also increase "unprotected sex with multiple partners".

[foldr]

Are you kidding around at this point? On average, people who are married are going to have sex with a smaller number of distinct partners than people who aren’t married. Gay marriage, if it has a significant effect on gay sexual behavior at all, will clearly reduce the risk of HIV transmission.

With regard to sibling marriage, the issue isn't sex per se but children. Although I am not myself deeply opposed to sibling marriage, there are many couples who strongly prefer not to have children outside of marriage, so it is quite reasonable to assume that banning sibling marriage will reduce the number of children of siblings. In contrast, it would simply be laughable to suggest that any significant fraction of gay people who have unprotected sex reserve unprotected sex for marriage. If that were so, HIV would not be a problem in the gay community!

So, no, there is obviously no reasonable comparison between your two cases, as a few moments of thought would make clear.

[LordKano]

Claimed societal interest in preventing harm to offspring born from inbreeding.

Does this mean that marriages between same-sex siblings will be permitted?

It's simply the fact that we find the idea of siblings having sex to be icky. Which is the same reason for the prohibition against same-sex marriage.

[DanBC]

Where "no evidence" means "lots of evidence".

http://www.genetics.edu.au/Publications-and-Resources/Geneti...

Etc.

[tzs]

> There's no evidence that sibling marriage results in defective offspring. It's simply the fact that we find the idea of siblings having sex to be icky

Bullshit [1].

[1] http://www.larasig.com/node/2020

[bdowling]

Did you read Your citation? Because it doesn't back up your assertion. It's says that for for first degree relations (brother-sister or parent child) the risk of death or severe defect increases 31.4% over the general risk. It doesn't say what the general risk is, but I assume it is relatively rare, on the order of 1 in 1000 or fewer. So risk to offspring from siblings would rise to about 1.3 in 1000. I would hardly call that proof that sibling marriage results in defective offspring.