Why shouldn’t you marry your sister?

[SoylentGreen]

Those who oppose homosexuality bring up either religion or "the yuck" factor to support there stance.

Well, here is another case, incest. Is there any reason not to support relatives marrying each other beside the religious and "yuck" factor?

In the animal world reproduction between close relatives is very common. In fact it was fairly common in humans in historical times to preserve bloodlines or inheritance. Even Cain (in the Old Testament) may have married his sister.

Marriage of related individuals is still common in numerous societies including people from South-East Asia, Israel and Saudi Arabia.

Indeed the notion of negative effects of “inbreeding” don’t seem to have been present even in English communities until around 1888 (though marriage to a sibling is banned in Christian dogma). Thus current Western revulsion at relatives marrying may correspond more to echoes from the Eugenics programs of the early 20th century than to any long held community beliefs.

But say you marry your cousin (which is legal), and your child marries their cousin (on the same side). This gives your child and their partner a relatedness factor of 25% - the same as a half sister or brother. Continue marrying cousin to cousin for a couple more generations and, genetically, it can be equivalent to marrying a direct sibling.

This doesn’t mean that there will be genetic problems, just that the chance of them is higher. In fact if you look at the history of European royalty (with a history of consanguineous marriages) you can see some of the genetic problems surfacing - think Alexis - son of Tsar Nicholas II - who suffered from haemophilia. A visit to the Kremlin and look at clothing from the royal lineage, you will see that many of the queens had extremely small feet - another genetic abnormality.

Similarly in other closed populations where people generally marry relatives through religious or geographical isolation, genetic problems will increase in prevalence (amongst the Amish in Pennsylvania or in Hasidic Jewish populations in New York for example).

So there are some good reasons for banning incest. But many of the laws against it were laid down long before genetics was understood. So some other forces must be at play.

And now that our knowledge of genetics is increasing should we not review those laws?

[prejudged_Fire]

Originally, yeah I guess it was banned due to the yuck factor and shouldn't have been. But now that we know the genetic risks, are you proposing that we make incest legal?

[Thanatos]

Quote by: prejudged_Fire Originally, yeah I guess it was banned due to the yuck factor and shouldn't have been. But now that we know the genetic risks, are you proposing that we make incest legal?

I wouldn't be surprised if they had some inkling of the genetic factors. They'd see people having children who appeared to have been subjected to a divine curse and I bet that's where the religious element came from.

[Dan_77]

Quote by: SoylentGreen And now that our knowledge of genetics is increasing should we not review those laws?

Yes, and should probably strengthen them, given what you stated and what we currently know about the ability to pass on genetic disease through close relations.

[SoylentGreen]

Firstly allow me to post the link I got this info from origionally. My apology I forgot to put it in.
Why shouldn’t you marry your sister? « Quarks, Quirks and Quips

prejudged_FireBut now that we know the genetic risks,

So what are the genetic risks?
The Straight Dope: What's wrong with cousins marrying?

The problem isn't cousin marriage per se, however, but rather how many such genes are floating around in the family pool. If the pool's pretty clean, the likelihood of genetic defects resulting from cousin marriage is low. A recent review (Bennett et al, Journal of Genetic Counseling, 2002) says that, on average, offspring of first-cousin unions have a 2 to 3 percent greater risk of birth defects than the general population, and a little over 4 percent greater risk of early death.

2,3 or 4%, doesn't seem like that great a risk. And with our knowledge of understanding how genetics work the risk factor is being reduced.

The U.S. is virtually alone among developed nations in outlawing marriage among first cousins. European countries have no such prohibition. In some cultures, particularly Islamic ones, first-cousin marriage is encouraged. Even in the U.S. laws forbidding the practice are far from universal. First-cousin marriage is currently illegal or restricted in 31 states. (Some states allow it if there's no chance of procreation--interesting in light of conservative opposition to gay marriage on the grounds that the institution's function is to produce children.) It's legal in the rest--and no, Kentucky and West Virginia aren't among the permissive ones. Try California and New York.

Doesn't it seem more a case of america , please try to keep up with the rest of the world. Or at least try to be consistent when arguing against gay marriage.

[prejudged_Fire]

2,3 or 4%, doesn't seem like that great a risk.

It does to me, and hopefully to any other sane person who wants to have a healthy child. Besides, these are the risks for relations with your cousin, not your sister, which is what you asked in the OP.

Doesn't it seem more a case of america , please try to keep up with the rest of the world.

So because the rest of the world is doing it, America should too? What was that thing my mom always used to tell me, something about jumping off a bridge?

Or at least try to be consistent when arguing against gay marriage.

That's off-topic.

[tinybear]

Lot had children with his daughters did he not?

[prejudged_Fire]

Lot had children with his daughters did he not?

Not sure, but according to my former Christian faith, God allowed incest at first when there wasn't much of anyone else around to mate with. After the population grew to a certain extent, it was no longer necessary and thus forbidden. I believe this was one of the changes made when the Mosaic Law was done away with, but I could be wrong.

[Barnicals]

I think that if incest was allowed in certain situations, such as if there was no chance of a genetic screwup whatsoever, everybody would get in on it, and you would end up with widespread genetic defects.
I think that the chances of having genetic defects is the biggest reason that laws against it are still around.
But yes, I do find it pretty yuck. It's mentally associated with molestation and paedophilia for me.

[SoylentGreen]

prejudged_FireIt does to me, and hopefully to any other sane person who wants to have a healthy child. Besides, these are the risks for relations with your cousin, not your sister, which is what you asked in the OP.

Don't take the OP literary this is about the incest law which covers up to 1st cousins.
Degenerative genes can be passed on even in normal marriage, the risks can be tested for so if approached intelligently then there is little risk.

So because the rest of the world is doing it, America should too? What was that thing my mom always used to tell me, something about jumping off a bridge?

I am not asking america to. all I am saying is this seems to be another case of lazy moral conservatism in america rather than a logical sensible approach to marriage.

Or at least try to be consistent when arguing against gay marriage.

It is relative to the topic in that you can not even argue consistency within your laws.

Not sure, but according to my former Christian faith, God allowed incest at first when there wasn't much of anyone else around to mate with. After the population grew to a certain extent, it was no longer necessary and thus forbidden.

Ok so either your laws are based on christian faith or it is a yuck factor.

[SoylentGreen]

BarnicalsI think that if incest was allowed in certain situations, such as if there was no chance of a genetic screwup whatsoever, everybody would get in on it, and you would end up with widespread genetic defects.

Your kidding? Do you really believe that if the law was changed then suddenly every brother, sister or first cousin is going to get themselves married, just because it's become legal to do so.
How many times does it happen? Not that much , but when it does why should it be illegal.

[Gods_Mercenary]

Not sure, but according to my former Christian faith, God allowed incest at first when there wasn't much of anyone else around to mate with. After the population grew to a certain extent, it was no longer necessary and thus forbidden.

You might be closer to the mark than you think given that I saw an interesting documentary which essentially said that in times when the human gene pool was bottle necked by disaster or whatnot, mating with close relatives became common, but that due to the restriction of diversity, it made such relations more potentially harmful for modern humans. At any rate, it's in the species' interest to spread the genes around and diversify. Whether it's legal or not, mating with a close relative without screening your genetics for potential hazards (a common practice) is irresponsible, especially if a history exists in your family of genetic disorders.

[The Bacon Guy]

Quote by: Soil So there are some good reasons for banning incest. But many of the laws against it were laid down long before genetics was understood. So some other forces must be at play.

Instinctive revulsion to an act which threatens your species’ gene pool. This trait would preserve the genetic fitness of an individual's offspring and therefore be perpetuated throughout the generations until we have a near-universal "yuck" response to the idea of incest.

Also, there's a theory in psychoanalysis that having more than one sexual relationship within a family causes strain and is therefore undesirable. This also could explain the development of the "yuck" response.

Quote by: Soil And now that our knowledge of genetics is increasing should we not review those laws?

Although we've established that there are sound reasons not to be banging your sister, I don't agree that it should be illegal to practice incest. First of all, not all couples want to have children and an incestuous union is therefore not necessarily going to be endangering a child.

Also, more importantly, it is not at all consistent with the way we treat other relationships. It is not, under any other circumstances, a crime for two people with a risky combination of genes to have sex or marry. The risk of a child having Down’s syndrome increases greatly with the age of the mother, yet we don't set an upper age limit for sex or childbirth.

The only genuine reason incest is treated differently is because of the instinctive revulsion people have towards it. The issue of genetics is a red herring thrown in to try to rationally justify this revulsion and therefore make banning the practice of incest seem more palatable.

It's the same with so many other things. People begin with their response to something and then attempt to find a way to rationalise it, instead of doing things correctly, i.e. the other way round.

[Jack]

Oh, what the hell, let's add a bit more diversity into the gene pool. As long as your partner is consenting and of an age that we agree upon as the minimum, why worry about their relationship to you. However, I'll have to use someone else's sister, I don't have one.

[SoylentGreen]

The Bacon GuyInstinctive revulsion to an act which threatens your species’ gene pool. This trait would preserve the genetic fitness of an individual's offspring and therefore be perpetuated throughout the generations until we have a near-universal "yuck" response to the idea of incest.

Historically incest has not only been acceptable but among royalty a must. We can thank christianity for making it unacceptable and giving it the yuck factor.

The only genuine reason incest is treated differently is because of the instinctive revulsion people have towards it. The issue of genetics is a red herring thrown in to try to rationally justify this revulsion and therefore make banning the practice of incest seem more palatable.

Agreed the genetics is not an issue, the revulsion is.

[The Bacon Guy]

Quote by: Soil Historically incest has not only been acceptable but among royalty a must. We can thank christianity for making it unacceptable and giving it the yuck factor.

Social factors can and do overcome genetic factors. That doesn't mean the genetics aren't there or that they're not active in the majority of cases.

And I don't think you can blame everything on Christianity: countless non-Christian societies have taboos against incest. Christian morals aren't generally original; they're simply codified versions of the morals of the time.

[SoylentGreen]

Inbreeding is no more harmful than outbreeding unless inbreeding is practiced erratically in an otherwise outbreeding population. In outbreeding populations, mates are less likely to share close ancestry and thus the same harmful recessives traits. In this kind of reproductive system, recessive genes do not wash out of the population and thus accumulate as a large genetic load. The result can be the manifestation of harmful characteristics in the offspring of mating relatives.

For most of human history, breeding populations were small and isolated, and the community often practiced cousin marriage. The results were a relatively homogenous population of inbred individuals. Such homogenous populations are also common in other species . It is unlikely, therefore, that a naturally selected mechanism would evolve to prevent incest/inbreeding.

[Barnicals]

Quote by: SoylentGreen Your kidding? Do you really believe that if the law was changed then suddenly every brother, sister or first cousin is going to get themselves married, just because it's become legal to do so. How many times does it happen? Not that much , but when it does why should it be illegal.

Well, not initially, but as time went on, I'm sure it would be much more common and acceptable.
As a side note, was this issue raised because of the episode of 20/20 last week?

[SoylentGreen]

Quote by: Barnicals Well, not initially, but as time went on, I'm sure it would be much more common and acceptable. As a side note, was this issue raised because of the episode of 20/20 last week?

Fraternal marriage was normal in ancient times. Recessive genes don't just appear they have to be passed on. If a couple does not have them they don't get passed on . If they do then precautions can be taken.
Most of euurope and asia practice cousin marriage .

No, actually I missed that episode, but would have liked to seen it. This is more an answer to a theist here who complained my morals were so low I would even consider fraternal marriage.

[The Bacon Guy]

Quote by: Soil Inbreeding is no more harmful than outbreeding unless inbreeding is practiced erratically in an otherwise outbreeding population. In outbreeding populations, mates are less likely to share close ancestry and thus the same harmful recessives traits. In this kind of reproductive system, recessive genes do not wash out of the population and thus accumulate as a large genetic load. The result can be the manifestation of harmful characteristics in the offspring of mating relatives.

But in any single union within an outbreeding population, the likelihood of two harmful recessive genes coming together is much smaller than with an inbreeding population. So those members of the population who outbreed are more likely to have healthy children and therefore to perpetuate their genes, than those who inbreed.

Quote by: Soil For most of human history, breeding populations were small and isolated, and the community often practiced cousin marriage. The results were a relatively homogenous population of inbred individuals. Such homogenous populations are also common in other species . It is unlikely, therefore, that a naturally selected mechanism would evolve to prevent incest/inbreeding.

You're supposed to provide a source for quoted material; not try to pass it off as your own.