scientific study about incest?

[KvHagedorn]

Originally posted by James_D
Well the Incest isnt a direct link to malformations, but it is a cause in increased frequency. Because of reduced genepool. The best example is the British royal family. They suffered greatly from Clotting deficiency disease, which is a X-linked recessive gene. The frequent inbreeding in the royal family lead to an almost certainty that the males would have the disease, while the females would be carriers.
And also the indian example is just another example of decreased genepool. And therefore an increase in recessive gene diseases will show.
In Norway there is also a slight problem with the pakistani population were, cousins inbreed, and we have an increase in resessive diseases and malformations.
So it's not totally correct to say that inbreeding leads to malformations, but the genes for resessive diseases will be more appearant among the inbreeders.


james.

Sorry for any spelling mistakes, I'm tired..

I had posted something about this here. Check the link for Prince Henry and Princess Irene. They were first cousins, as were their grandparents, Queen Victoria and Prince Albert. Two of their three sons had hemophilia. I had some info wrong there, apparently. I had thought that prince Albert actually had the disease, but it was Victoria who passed on the recessive gene, which her granddaughter Irene also carried. Had Henry's mother Vicky gotten Victoria's bad gene as well, Henry and Irene could have had the rarity of a hemophiliac daughter.

Here is a link to an abbreviated ancestral chart tracking the gene. Henry and Irene's sons are the first group in row VI there.

[Brian Ellis]

Drslump

There is plenty of evidence why you shouldn't marry within the family. It's much more frequent for daddy and daughter to have it off than brother and sister. I'm sure, if you do a search, you will find that the offspring of both these types of relationship abort naturally at roughly three times the rate of non-related couplings. This is nature's way of dealing with gross malformations.

If you have bred dogs, you will know that the most robust breeds are not too inbred. There is another problem bugging naturalists at this moment. The gene pool of cheetahs is insufficient to ensure survival; they have to be very careful to try and breed those in captivity with the most diverse specimens possible and then to try to introduce these into wild ones. The problem is that there are pockets of cheetahs, and there has been little intermingling at the time when they were more diverse, so they have degenerated. It is believed that the difficulty of breeding the Giant Panda is also related to small gene pools, causing abortion.

I'm categorically opposed to intermarriage at less than the third level of consanguinity and the laws forbidding it are founded by experience and observation, but also later proven to be sound scientific sense, as shown by Mendel and many others. It matters not whether these laws were started for religious or secular reasons: the facts are there.

As for Adam and Eve, this, of course, is a pure myth to explain our presence on earth. And I say this as a very poor, lapsed Christian. The fundamentalists who believe in the truth being in every word of the Bible are every bit as wrong in their ways as Islamic fundamentalists or any other kind, IMHO. I once knew an atheist fundamentalist who preached his gospel loud and clear at the drop of a hat, but who would not hesitate to say "Oh my God!" or "Christ" if he was surprised or dropped a hammer on his toe

[Paddy]

LOL Brian (the terrible)

[Brian Ellis]

Paddy

I also knew a moderate atheist who used never to say, "there is no God" too loudly, in case He heard

[DukeP]

There are MANY valid scientific reasons for avoidance of inbreeding.

The effect of any particular inbreeding depends strongly on the previous history of the family.

I think I have posted a rant on this before, here at MURC, but never mind

Short: An outbreed population are more susceptible to dire effects than an inbreed population: The inbreed population have allready had to face the dire consequences!

Case in point: The population of large cats, kept in various zoo's. Most of these have been inbreed for a while, and some (like the aforementioned cheetah) are to a large part naturally inbreed. The effect of this is A) reduced fertility, and B) reduced resistance to diseases (a common cold originating in domesticated cats killed a great many zoo speciemens, not that many years ago). But, given isolation and care, these zoo specimens can still be used for breeding.

If one where to do the same experiment with the much more outbreed human population, the effects would be hugely more drastic (and happen in a shorter span of generations).

Remember: diversity build resilience!
If inbreeding was less of a problem, why have sex at all? In reality, we are wasting half of our biomass on something basically unproductive.

Case in point: 99.99% of all cockroaches are female. Males are almost exclusively found in the areas around Thailand and Malaysia. Cockroaches abroad are therefore not only inbreed (actually they are not, not strictly speaking), they are virtual clones of an amazingly FEW founding mothers.
That we havent as of yet found any decent way to take advantage of their lack of adaptebility only speaks to our own lack of creativism and, of course, cockroaches allready wide and diverse defenses.



/rant

~~DukeP~~
Biologist (hope you can tell).

[James_D]

Originally posted by DukeP
[B]Case in point: The population of large cats, kept in various zoo's. Most of these have been inbreed for a while, and some (like the aforementioned cheetah) are to a large part naturally inbreed. The effect of this is A) reduced fertility, and B) reduced resistance to diseases (a common cold originating in domesticated cats killed a great many zoo speciemens, not that many years ago). But, given isolation and care, these zoo specimens can still be used for breeding.

First of all I don't know the biology of Cats, just humans, so I wondered how you can claime reduced fertility? The fertilty rate would still be the same, but their abortion rate due to severe malformation would increase. That's at least the point with humans. There are of course cases where you have diseases that are linked to fertility, which will be ressesive and sexlinked.

And for immunology, well again in humans we have aprox 10^9 different antibodies pr persons. Many of these are similar for people of same family, but they are not all predetermined by birth.
Leukocytes, are among the few cells, that alter their genome, while the body lives.

If one where to do the same experiment with the much more outbreed human population, the effects would be hugely more drastic (and happen in a shorter span of generations).

And why on earth would this happen? I don't see how you can say this... There is not a big difference in the meiotic divitions of the oocytes and spermocytes, between animals and humans. And the humans has a much more complex genome than most animals. Though the number of genes arent that different.
And if the the population is outbreed, well then they have a bigger variation when they start, so it can last longer. Because of the variations in the meiotic divitions.

James

[DukeP]

Just a short answer to james:
Reduced fertility covers both some examples of autoimunities, as well as what you would call spontaineously aborts.

A well outbreed population generally (although not neccesarily) carry a greater number of defects, since the odds of homozygosity is that much lower. If nothing removes genetics defets, they automatically accumulate. Inbreeding as well as (more oftenly) enviromental stress removes genetic defects. A hugely succesfull, sexual and outbreed population tends to accumulate a huge number of defects, all things being equal.

Oh, and not all defects are bad, some improve fitness, although only in outbreed populations (eg. Sicle cell syndrome).

Got to go.
~~DukeP~~

[James_D]

Originally posted by DukeP
Just a short answer to james:
Reduced fertility covers both some examples of autoimunities, as well as what you would call spontaineously aborts.

Oh, and not all defects are bad, some improve fitness, although only in outbreed populations (eg. Sicle cell syndrome).

Thanxx for the swift reply, very interesting, But I still have some problems with your theory, as for the autoimunities. IgG's are the only ones able to cross the placenta, and they are very seldom involved in autoimmune diseases and since there is no autoimmuine reaction against the mothers own dna, only the fathers dna(e.g: Rhesus - mother, farher + and + fetus.), I don't see your point. And you can't include the spontan. abortions linked to malformations(genetic cause) of the fetus in this group.

And for your defects theory, yes you have a greater sum of various defects present in the population, but for as for individuals there is less chance of 2 having the same genes.

And yes I agree, defects aren't only bad, eg. the sickle cell poplulation linked to Malaria.

James.

[Paddy]

Ig G's are the only ones able to cross the placenta, and they are very seldom involved in autoimmune diseases

*edit*
However, the prevelance of autoimmune diseases will be increased in an inbred population for the same reason as you stated earlier - decreased diversity

[Paddy]

And yes I agree, defects aren't only bad, e.g. the sickle cell population linked to Malaria.

um... I don't doubt that carrying the sickle cell gene provides an evolutionary advantage over malaria, however I wouldn't want it

*edit (again)*

Those African prostitutes that I mentioned have a naturally low CD4 count (off the top of my head). Again, whilst that has provided them with a specific advantage over the HIV virus, it will be deleterious in the long term.

As far as I understand, most deviations from the 'normal' provide only specific benefit at the expense of long term adverse consequences. Perhaps someone here can suggest a mutation that proves otherwise???

Paddy

[agallag]

Originally posted by KvHagedorn
What happened to the fine chica you posted pics of here some time ago?

We broke up a few months ago...

[Greebe]

There are so many neurological defects passed on through inbreeding it's not funny. One should never tempt fate, or you just might get more than you are bargining for. Many are specific to culture and or religous backgrounds. Just ask ANY neurologist sometime. Most times these are far far worse than infertility or your run of the mill physical defects.

[James_D]

Originally posted by Paddy


*edit*
However, the prevelance of autoimmune diseases will be increased in an inbred population for the same reason as you stated earlier - decreased diversity

Well I think we are both a bit right, if you also saw my earlier post, that leukocytes, do go through a DNA alteration, this will contradict the autoimmune cause. And also all Leukocytes are screened before they are let loose, so that the leukocytes are able to differ from self(body) and nonself(forreign). And the autoimmune reactions happens usually when the screening fail, or you also have a specificity increase when the leukocytes have arrived in the lymphnodes, and have met an antigene which it has a receptor for. Though interesstingly enough there are B1 leukocyres (CD5 +) (Normal is B2 (CD5 -) which produce IgM's that are targeting self. This reason is not entirely understood, but, the main theory is to hinder Autoimmunereactions, by eliminating subst's(antigenes) released from apoptotic or by cell lysis. e.g Cytochrome C. And the IgM don't produce an cell lysis if they bind to a cell, they just bind, and nothing happens except that no other antibody can bind the antigene. and they are usually secreted with the urine, or bowl.

However there will be an increased nr of other diseases, and there is the possibility for defects in the screening. Though not very likely. And this is equally likely to happen in the "outbreed/normal population"


James..

Hmm.. don't really know if I clearified anything but I hope so,,

[James_D]

Originally posted by Greebe
There are so many neurological defects passed on through inbreeding it's not funny. One should never tempt fate, or you just might get more than you are bargining for. Many are specific to culture and or religous backgrounds. Just ask ANY neurologist sometime. Most times these are far far worse than infertility or your run of the mill physical defects.

hehe what do you think I'm studying..


James.

[James_D]

Originally posted by Paddy
um... I don't doubt that carrying the sickle cell gene provides an evolutionary advantage over malaria, however I wouldn't want it

*edit (again)*

Those African prostitutes that I mentioned have a naturally low CD4 count (off the top of my head). Again, whilst that has provided them with a specific advantage over the HIV virus, it will be deleterious in the long term.

Paddy

Yep I have heard about it, and also there are some gay persons in the US, which have the same CD4 negative T helper cells, which neither contract AIDS. But there are also strong indication that though they do not get affected they can still be carriers of the HIV. For the CCR5 and CXCR4 also can allow HIV to infect a cell. Which cells then can acts as reservoir. Though not becoming sick, just giving the disease to others. These cells can be neurons, astrocytes etc..

And why will it be deleterious in the long term???

Nobody knows that for certain.


James.