Incestual conception

one_raven

one_raven

God is a Chinese Whisper
Valued Senior Member
I am doing some research for a book idea I have...

What are the actual biological facts about offspring produced by incest?

I have heard it causes deformity.
I have heard it makes the offspring more likely to have this disease/affliction/problem etc.

I have also heard that it is all bunk, and there is no actual negative side (biologically speaking) at all.

Do those risks of "side effects" (if there are any) increase/decrease with relations?
For example, a child concieved with your sister/brother, or a child concieved with your father/mother, grandparents, great grandparents, cousins etc?
If so, would it make a difference if it is your sister or your third cousin if the whole family were strictly incestual? No outside genes?

Then there is evolution...
What about incest over a long period of time?

Let's say they strictly "keep it in the family" for hundreds of generations.
What would be the benefits/drawbacks long term?

If there are actually physical drawbacks, does anyone know why?

As far I understand, the common belief in the scientific community is that all humans can be traced back to a single common source (or tribe) in Africa...
How does that really differ from generations of incest?

Thanks.
 
I have read that it is simply that if your family carries a genetic disorder, by having offspring with a non-relative you have a chance of inheriting the "good" gene and if you breed with a relative that chance is decreased since both parents are likely to have that same "bad" gene.

Does that hold up?
 
I came across this interesting article about cat breeding.

It is basically saying that what I said in my last post was true and it really just comes down to genetic traits.

So if you come from a family with a fenetic disposition to something "bad" you are more likely to pass it onto your offspring in an incestuous conception.

However, the reverse also holds true.
"Good" genes are also more likely to be passed.

Is this also true for humans?

If so, consider this hypothetical...

Two "perfect" human specimenes get together.
They breed, and all thier offspring only breed together keeping the bloodline "pure".
Would the offspring 200 generations later still be "perfect"?
 
one_raven:

<i>I have heard it causes deformity.
I have heard it makes the offspring more likely to have this disease/affliction/problem etc.</i>

It makes offspring more likely to exhibit diseases with a genetic basis.

<i>I have also heard that it is all bunk, and there is no actual negative side (biologically speaking) at all.</i>

False.

<i>Do those risks of "side effects" (if there are any) increase/decrease with relations?
For example, a child concieved with your sister/brother, or a child concieved with your father/mother, grandparents, great grandparents, cousins etc?</i>

The less genes shared, the less chance of bad effects on offspring. Parents share 50% of their genes with their children. Grandparents share 25% with grandchildren. Siblings share 50%. First cousins share 12.5%. This all assumes no incest in previous generations, of course.

<i>If so, would it make a difference if it is your sister or your third cousin if the whole family were strictly incestual? No outside genes?</i>

Depends how long the incest has been going on for, but a third cousin will always be a safer bet than a sibling.

<i>Let's say they strictly "keep it in the family" for hundreds of generations.
What would be the benefits/drawbacks long term?</i>

The major drawback would be a very depleted gene pool, making the entire population very susceptible to diseases and deformities.

<i>If there are actually physical drawbacks, does anyone know why?</i>

Less genetic diversity means less ability to cope with environmental circumstances.

<i>As far I understand, the common belief in the scientific community is that all humans can be traced back to a single common source (or tribe) in Africa...
How does that really differ from generations of incest?</i>

A single common ancestor does not mean a single individual. We're talking species there.
 
Thanks for your reply, James.

What about the hypothetical situation of the two "perfect" human specimens having offspring and having a family tree that never branches off?

Would "bad" genes develop and prosper in this family tree if they were not introduced by another genaeology?

It seems that if you have genetic problems in your family, by mating with someone that does not have that problem it reduces the risk your offspring faces.
On the other hand, if you are the one with the "better" genes, then you are placing your offspring at a higher risk by breeding below your gene pool.
So if your line has no genetic problems at all, then shouldn't inbreeding keep your genes pure and free of introduced genetic problems?
 
What about the hypothetical situation of the two "perfect" human specimens having offspring and having a family tree that never branches off?
Click to expand...

Well hypothetical it would work to a limit. The gene pool would virtually non-existent and perfection would be limited as in nothing can handle all possible situations perfectly or even survivable. After several generations genetic mutations would deepen the pool though after that its going to be like inbreeding.

So if your line has no genetic problems at all, then shouldn't inbreeding keep your genes pure and free of introduced genetic problems?
Click to expand...

I see what your getting at but in real life no one knows the quality of their gene pool. Many harmful genetic mutations remain hidden or recessive, because we a diploid we have 2 copies of every gene and a defective or dysfunctional gene can be covered by the functional one. If you inbreed though your chances of producing offspring that have 2 defective copies of a given gene (homozygous recessive) are much more likely then if you hybridize.
 
one_raven:

<i>What about the hypothetical situation of the two "perfect" human specimens having offspring and having a family tree that never branches off?

Would "bad" genes develop and prosper in this family tree if they were not introduced by another genaeology?</i>

Genes can alter by mutation and by copying errors, so they could certainly develop over long periods of time.

<i>It seems that if you have genetic problems in your family, by mating with someone that does not have that problem it reduces the risk your offspring faces.</i>

Depends what the problem is, but in general you are right.

<i>On the other hand, if you are the one with the "better" genes, then you are placing your offspring at a higher risk by breeding below your gene pool.</i>

Yes.

<i>So if your line has no genetic problems at all, then shouldn't inbreeding keep your genes pure and free of introduced genetic problems?</i>

Apart from the mutations and so on, yes. But as soon as one bad gene creeps in, the problem will be propagated, and nobody will be immune since they all have the same natural resistance to the effects of the new bad genes.
 
So, essentially, even if "God" :rolleyes: came down and created two perfect human beings (such as the mythical Adam and Eve), eventually, somewhere down the line, someone will end up with a viral infection, in-utero protien deficiency, fetal injury, blood pathogen etc and if their genetic make-up was altered by this, and they breed, then >poof< your gene pool has some stagnant water in it?
What else comes into play?

"Random" genetic mutations?
Phyical/Chemical/Medical reactions to environment (such as extreme heat, extreme cold, precipitation etc)?
I know that in modern society, many other aspects can come into play such as antibiotics, anti-bacterial cleaning solutions, artificially altered foods...


Let's say you do have a perfect pair.
They live on a tropical island and eat only natural healthy fruits and berries and they "keep in shape".
All that stuff you can do to keep your body healthy.
What other factors play a role?

What (real or hypothetical) precautions can be taken for such genetic line spoilers?
What (if anything) can be done to keep that inbred bloodline pure for many generations?
 
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Random genetic mutations you know like back ground ionizing radiation, free radicals, other mutagens naturally produced in all foods and even in the body. No matter what your gene pools going to get deeper after repeated breedings because mutation always occurs.
 
OK.

Then let's take it a step further, if you don't mind getting too hypothetical here.

I just hired you to work for a think-tank assembled to produce the ideal pair of mating humans who will spawn the ideal genetic line.

The team you will be directing has unlimited resources at its disposal, time is not a factor, you have total freedom and legal immunity.
Your resulting "product" will adhere to a very strict diet, fitness and health routine.

What ways (if any) would you suggest altering the "typical" human genetic make-up to prevent genetic mutations to this or future generations?

How would the New and Improved humans differ from what we would generally consider a supremely healthy human being by today's standards, say an Olympic tri-athlete who has never been sick a day in his life.

What natural mutagens would you need to protect the subject from?
What other factors come into play?

If you DID create this pair, what (outside of his prescribed diet and health routine) could make him (or his ancestors) susceptible to these mutations?

This is getting too convoluted!!



Let me just tell you what I am trying to accomplish, and if you are interested, you can tell me if it is possible, how, and if not, why not.


Essentially, in this book (if you haven't figured it out by now) there was an original "perfect" man.
He had 12 perfect women as wives.
If you can trace your roots directly back to him and one of his wives (with no branches in the tree to any of the other genetic lines) you inherit his "ideal" condition.
Those of interbred lineage (obviously just about all of human existence) suffer the weaknesses common to modern humans.

How can I pull this off and still stay true (at least within reasonable standards) to modern knowledge of genetic understanding?
Or...
How could I hold this up as a refutation of modern understanding of genetics and a feasible alternative without "breaking" any rules?
This isn't really a science fiction piece, but for this one aspect, and I want it to be able to stand up to reasonable scrutiny.

Can you see any options at all for me to at least explore?
 
The offspring from an incestual breeding will have the genetic traits of the parents magnified. If those traits are a little shit in the parents they'll be alot shit in the offspring.
But at the same time if they are good traits they'll be even better in the offspring.
Dog breeders, particularly working dog breeders(hunting, herding, personal protection, fighting[boo]) wouldn't not inbreed there line a little and expect good dogs.
If they come accross an exceptional dog they'll breed him to his daughters and grandaughters if possible, to reinforce his quality genes into their line. This does not have negative affects at all if it is done proffessionally, it has great affects. You HAVE to do it to consistently produce good dogs.
Obviously it would work the same in humans, but it just so happens that the people who decide to have sex with their daughters are invariably low life scum with poor genes(not surprising), so deformed children pop out and everyone assumes inbreeding leads to deformed children. Buts its a bit more complicated than that.
Too complicated for me to understand, I've heard the scientific description but I've already translated it into me-words in my head so I can't remember what it was.
I'm right though, well thought out strategic inbreeding with top quality specimens is beneficial but hap-hazard inbreeding with lesser specimens produces genetic disasters.
 
Perfect Inbreeding runs a risk of total extinction of that species if a fatal contagious disease finds a loophole in genetic structure.
 
Just thoroughly read the thread(feel bad for not doing it in the first place) and ok what i said has already been figured out.

Ok I think I see where you are going.
Would 1 super man and 12 super women produce a super line of humans if they had no outside interference for many generations?
I don't know.
That isn't exactly how dog breeders do it and I say that because they are pretty serious about it and really do know what they're doing. I'm not talking about showdogs but dogfighters in japan and boarhunters in australia etc. They independently developed the same method of producing "super dog" lines from years of trial and error.
Ofcourse, it could be because they don't have 12 perfect females, if they did they might work like your scenario.
But what they do is first discover "the perfect male" from testing him in the field(whatever it is). Because truely exceptional individuals are so rare they don't just breed him once to the best female they can find, they breed him to the best female, and then breed him to his daughters and grandaughters.

The offspring of that will be 7/8 him, what they are trying to do is get as close to a clone of him as possible because he was so successful.
Now I'm not great at math but with your program idea I think the offspring are always only going to be half the original superman.
But you did say that all the females were perfect also so I don't really see any problems so far, you can't really go wrong with that.

But, and this is what I've been wanting to get at(sorry), for some reason both japanese dogfighters and australian boar hunters(and others) will outcross after the third generation, meaning introduce fresh blood.
The tried and true formula is to inject new blood into the line every 3 generations.
Now this could be because problems arise, but I think it is because of a thing called hybrid vigour.

Even with all that work that third generation aren't that crash hot, they are good but usually less good than the super dog that was started with, for some reason his legacy is revived when his offspring that is 7/8 himself is bred with a dog as unrelated as possible(bearing in mind that it should be a quality specimen itself).

The offspring from this in theory should be another super dog like the one you started with or ideally, and as is often the case, even better, and you start the pattern again using this dog as your new foundation.
The champions pop up every 4 generations and they should get better each time but the ones in between usually aren't that special.
They are great quality specimens just not necessarrily as good as the foundation super dog.
Which I don't think can be consistently bred.

Not trying to be difficult, I'm fairly sure your idea would be producing better humans than hap-hazardly bred humans, so in your book they could still stand out as super humans in comparison.
But I don't THINK they could all be as perfect as the original super man. Well I'm kind of just guessing based on what I know about people breeding for super dogs.
To be honest I really don't know how your idea would work out, I shouldn't be wasting so much of your time I'm just interested in this subject.

But yes if you are going for scientific accuracy I do think that your breeding program would eventually get a little stale without fresh blood. Don't hold me to that though, with 13 perfect specimens as the foundation the rules might change a little, not sure.
 
Usually in animal breeding there are two techniques used.

LINE BREEDING is breeding the children back to their parents, or more occasionally their siblings. If you don't have a fancy genetic testing lab, this is one of the few ways that you can get an idea of what traits an animal has.

Line breeding is important because it permits you to get a trait back quickly, in the case (for instance) that it is recessive.

Let's take rex cats, for instance. The rex trait is a recessive allele gives the cat curly hair instead of straight (there are several kinds... I won't go into it). Now, let's say you have ONE rex cat, and you want to breed a whole army of rex cats. How do you do it?

Let's call him Rex. So, first you breed Rex to some non-rex cat Amy. Amy has a litter of non-rex kittens. This is the F1 generation.

Since Rex is the only full rex cat we have, the F1 boys aren't much use at the moment 'cause they can't breed with him. So, we breed the F1 girls back to Rex.

NOW! The Rex+F1 cat pairs will all have Rex's copy of the rex allele. However, the F1 cats only have one copy (which is why they don't express it - it's recessive). So, each kitten in the Rex+F1 litters will have a 50% chance of getting the F1 cat's copy of the rex allele (and 50% chance of getting the F1 cat's copy of the normal). So, about 50% of the cats in the Rex+F1 litters will be rex, and 50% will not.

This is the F2 generation. Any of the cats that express rex can then be bred together and produce only rex kittens.

(If you bred the siblings from the F1 generation together, because it is a recessive allele, you would get 25% non-rex, 50% rex carriers, and 25% rex in the F2 generation. So, breeding back to Rex gives twice the probability of getting rex kittens.)

This is how line breeding, which in humans is usually called inbreeding, can be used to reproduce a trait from a single individual.

Why is this a problem? Well, let's say that Rex only had one copy of the rex allele instead of two. He would look like a normal cat, indeed, he would be one, but he would still carry for the rex allele.

Now let's say that it is still a recessive allele, but instead of rex, which causes curly hair, it is the EH gene which causes Exploding Head disease, a condition that makes the kitten's head violently explode at the age of two weeks.

If you breed the cats as shown above, the F1 kittens have a 50% chance of inheriting one copy of Rex's EH allele. Then, when the F1 kittens are bred back to Rex, half of them will be EH carriers, as well as Rex. The F2 generation will therefore have 25% normal kittens, 50% EH carriers, and 25% cats with the EH expressed (who will die as kittens).

Normally, a chance mutation in a single animal will not also occur by chance in the animals that they breed with, but if line breeding is used in this way it can reproduce the mutation in both breeding parents for the F2 generation.

So... in animal breeding you also OUTCROSS, which is breeding to unrelated animals. This permits the breeder to try to assimilate good traits from other individuals into their own breeding line, either to enhance the animals therein, or to try and displace bad traits from the line.

Because of concerns about mutation expression (as I mentioned in the line breeding description) human beings are generally encouraged to only outcross. However, this largely limits human breeding to dominant or visibly expressed traits, because humans don't have any kind of breeding program that goes beyond one generation.

Anyway, you should bear in mind that nearly any word on breeding programs in humans is immediately attended with the scream of EUGENICS!

Whereas the above described process of line breeding for desirable traits is standard practice in animal breeding, and has brought us all of the strange dog breeds that we have today; imagine the effort required to turn a wolf into a chihuahua, or an Italian Mastiff... what untold potential do humans have?
 
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Sorry Dr Lou... you posted while I was typing... didn't mean to criticize ya. I'll go back and edit in a sec.

I suppose I should add that a proper breeding program is pretty complicated and works a lot better with several lines. If you want a dog with wings and horns, it's easier to breed for just wings in one line and just horns in another, and then bring the two together after they've been developed. (This develops the traits concurrently instead of seperately, which is much faster... the major problem in breeding is TIME, since the measly 80-year lifespan of a human being is only about enough to see 4-5 generations of the breeding program.)

There are a couple of practical concerns with organized breeding of this kind, even if you can perform fine-grained genetic testing.

The time constraint, as I said before, is a real consideration; this is why, in Dune, the Bene Gesserit were an entire religion devoted to the pursuit of a breeding program...

The monoculture problem which everneo mentioned - a weakness to a hitherto unknown virus would be present in the entire "perfect" population.

In the case of outcrosses, 50-75% of the offspring do not carry the traits that you are trying to breed for and have to be kicked out.

Also, since the genetic properties of a human being are kind of open-ended, the idea of a perfect superperson might be a little presumptuous...

Dr. Lou: in the case of a lot of traditional dog breeders, they don't have any formal education in Mendelian transmission genetics, which can be very helpful in isolating specific traits. But, people are usually breeding for "incomplete dominant" traits - that is, they want the animal to be bigger or faster or juicier or something like that, and those traits aren't isolated quite as easily by the technique I mentioned above... but it's still quite helpful.
 
I would never put together any two humans to breed the next generations. I would just give them advanced genetic engineering equipment and a lot of artificial wombs. Have them grow the next generations like plants.
 
Yeah, but that's frickin' expensive... my method just needs a big house and plenty of note paper.
 
So would this be feasible:

If so, why?
If not, why not and what alternatives might I explore?

There was this one perfect man.
He had 12 perfect wives.

Each decendant of a "pure" line back to mom and dad (without interbred branches) inherit all the traits of mom and dad, but with each generation (or 3-4 generations), there is slight degradation (from natural mutagens, viral infections, in-utero infections etc).
In the beginning, since they had near-perfect genes, these effects were basically negligable.
The effects would build up over time due to the parents on each side having the same weaknesses.
So...
(I am not planning on using this in the book, but let me just take it as an example...)
Let's take the Biblical Adam and Eve again.
They lived to what? 930 years old?
So maybe, 12 generations later, the life expectancy might be 900 years old.
Adam and Eve started with a natural immunity to all diseases, but over years, new strains developed that their offspring were not equipped for.
Some of them survived and adapted an immunity, but in order for that to happen, some sort of genetic mutation would have to take place.
Some of those genetic mutations would have adverse side-effects.
Those that didn't get the mutation would die off if they get the disease, but might mate before hand.
Now you have three different genotypes (right word?) in the line, and those blend... and so on and so on...

Those that interbred would have mutated at a higher rate since they had radically different genes to begin with.

Now, 20,000 years later, those that are purely inbred would be closer to the "perfect parents" than those that have an interbred line.

Will that work?
Where are the flaws?
What should I pay special (or more) attention to to make it work?
 
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There aren't enough Biologists on here at night! :)

A little more info about what exactly I am trying to accomplish with this....

I want it to be a (hopefully) feasible alternative to what we currently consider reality and I would like it to be able to stand up to scientific scrutiny.

So, I don't mind if people say, "That's not how it happened" as long as I cover enough bases to force them to say, "Even though that's not how it happened, it does hold true to the available facts."

I also want it to be able to stand up (somewhat) to religious scrutiny, so I am trying to inject some of the aspects that a lot of the major religions have in common, some of the big aspects of what the major religions disagree on and offering a syncretic solution to them all.
Kind of like saying, "Yeah, you were all right, but you were all wrong, too."

So when people look at this proposed reality they can at least say, "Well, I can't really prove it wrong, so I guess it's possible" and hopefully I will be convincing and thorough enough so some people will say, "Yeah, I can see how that could be true." at least enough to be able to buy into this reality for the purpose of buying into the story in the books.

Then I am going to try and set a (hopefully) compelling story about these two major characters in this alternative reality I have created.

Make sense?
 
All of their genomes would change or "deteriorate" at about the same rate; the ultimate result would be that any individual would be no more "pure" than any other, although it might be possible to recover lost combinations of traits through selective breeding.
 
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