Kiss me sister!

[chequita guevara]

Wiki for help

http://en.wikipedia.org/wiki/Inbreeding

Results of inbreeding

Inbreeding may result in a far higher phenotypic expression of deleterious recessive genes within a population than would normally be expected.[1] As a result, first-generation inbred individuals are more likely to show physical and health defects, including:

* reduced fertility both in litter size and sperm viability
* increased genetic disorders
* fluctuating facial asymmetry
* lower birth rate
* higher infant mortality
* slower growth rate
* smaller adult size
* loss of immune system function.

The key words here are far higher than would normally be expected. Let us assume, for example, that a particular birth defect appear in the population about 1% of the time. Among incestuous couples, it appears 2% of the time. That's a 100% increase, far higher than normally appears in the population. It still isn't all that likely to occur.

[Wezil]

That's some serious thread necromancy.

Without reading the entire thread again (but wanting to add to Che's comment...)

Non related couples sometimes have much higher chances of producing offspring with birth defects yet they aren't denied the right to marry. The "mutant offspring" argument is a cover for something else.

[DanS]

In Korea it's illegal for anybody with the same family name

This can't be right. What the hell do all the Kims do?

[KrazyHorse]

Mutant offspring among relatives is actually a pretty serious problem. The rate of serious handicap/early death among the offspring of incestuous (parent-child or sibling) couples is close to 50%

[Wezil]

Cite?

[Japher]

Probably West Virginia

[DanS]

I can add some anecdotal evidence on closely-related marriages. Our Amish neighbors had 2 retarded kids out of 11. As far as I know, this is fairly common, unfortunately.

[Wezil]

Dan - I've seen the same thing when I was around the Mennonites. They are a somewhat closed community of continuous inbreeding however. Not quite the same thing as the the examples in this thread.

I had heard recessive genes carried by both parents can lead to a very high rate of birth defects (not my area of expertise to say the least). A quick search found this:

If only one parent passes along the recessive gene for a disorder, the normal gene received from the other parent will prevent the disease. However, that child will be a carrier for the disease. Children of a carrier have a 25% chance of getting the disease if the other parent is also a carrier.

http://www.hmc.psu.edu/childrens/healthinfo/b/birthdefects.htm

As we can now test for many of these conditions, surely we should consider preventing them from marrying? 25% is pretty high. I have yet to hear that discussion.

[KrazyHorse]

Cite?

http://books.google.com/books?id=OW1nuQxcIQgC&pg=PA52&lpg=PA52&dq=incest+rate+of+serious+defects&source=bl&ots=qnwAsGBXKu&sig=nF4OVcAKw-GHvWtPOvVlWBmZkM0&hl=en&ei=1FyAStnZLMq3twfM--jcAQ&sa=X&oi=book_result&ct=result&resnum=1#v=onepage&q=&f=false

Has the excess mortality + severe defect rate as 31%

Further on in the same book they apply the fairly well-known excess mortality rate for first cousins of ~4% and through a model of the increased genetic similarity in sibling or parent-child offspring estimate 16-20% excess mortality

The incest taboo arose because incest led to consequences which even primitive societies could see.

EDIT: there are some other studies of the defect rate which you can feel free to google up, but this is NOT simply the difference between 1% birth defects and 2%. Incest has a dramatic effect on children's welfare.

[Wezil]

Interesting. As i say, science is not an area I know much about.

So what should our cutoff rate be? 25% still seems high to me.

[KrazyHorse]

Dan - I've seen the same thing when I was around the Mennonites. They are a somewhat closed community of continuous inbreeding however. Not quite the same thing as the the examples in this thread.

I had heard recessive genes carried by both parents can lead to a very high rate of birth defects (not my area of expertise to say the least). A quick search found this:

If only one parent passes along the recessive gene for a disorder, the normal gene received from the other parent will prevent the disease. However, that child will be a carrier for the disease. Children of a carrier have a 25% chance of getting the disease if the other parent is also a carrier.

http://www.hmc.psu.edu/childrens/healthinfo/b/birthdefects.htm

As we can now test for many of these conditions, surely we should consider preventing them from marrying? 25% is pretty high. I have yet to hear that discussion.

Requiring testing prior to all marriages affects far more people and seems to me to be a much more odious requirement than simply banning all sibling marriages. First cousin marriages are much less harmful

[KrazyHorse]

Wezil, it's not the ban on marriages among 2 carriers which seems wrong, but the testing required to apply such a ban.

[Wezil]

Testing wouldn't even be required in many cases as the carriers already know.

I was actually sitting here wondering on the intrusiveness of it (I suspected that was where we were going). I'm not sure of the protocol involved in getting married. Is a trip to an MD required?

A forced blood test is certainly intrusive but an argument can be made that the State inquiring into your lineage could be intrusive as well. The overall public good must be considered and quite frankly I am having a hard time seeing either 25% or 31% chance of a birth defect being in the overall public good. How far should the State be allowed to go to prevent this chance of a child (potentially) becoming a lifetime ward of the State? If it is none of their business in the one case, it should be none of their business in the other.

I think the ick factor is still the number one reason why it is legally forbidden.

[Wezil]

Wezil, it's not the ban on marriages among 2 carriers which seems wrong, but the testing required to apply such a ban.

Sorry, I type slow.

I DanS'd the above post as well (1st line). Corrected the muddle.

[KrazyHorse]

I'm not sure of the protocol involved in getting married. Is a trip to an MD required?

Not in QC. The woman who performed the marriage for my wife and I (unitarian minister) took photocopies of both of our birth certificates as well as signatures from both of us that we were legally entitled to blah blah blah. She then had to post an announcement of our intent to marry for 3 weeks prior to the ceremony in case anybody wished to raise a legal objection to our marriage (presumably if we were related or one of us was already married, or one of us was legally incompetent...hey, no jokes ). She filed to relevant forms with the QC government. On the day of we had to sign the marriage contract, along with witnesses. She filed that too, and a few weeks later we got the marriage certificate.