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Incestual conception

  1. Dec 29, 2003 #1
    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?

  2. jcsd
  3. Dec 29, 2003 #2
    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?
  4. Dec 29, 2003 #3
    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"?
  5. Dec 30, 2003 #4
    Incest increases chances of deformity because harmful recessive genes are more likely to be passed to offspring. This is true in humans and any animal.

    With interbreeding you get a lot of genetic diversity, which limits the effects of the bad genes.
  6. Dec 30, 2003 #5


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    It is true that having offspring with 1° relatives, such as parent child causes recessive genes to come to expression. There is a controversy though, if this still holds true for a niece and nephew getting children together.

    There was a tread quite a while ago, where I actually quoted the chances of the general public vs niece/nephew to get a sick child, they weren't too far off.
  7. Dec 30, 2003 #6


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  8. Dec 30, 2003 #7
    Good stuff.

    I posted this on my other biology forum.
    Let's where it gets me here...

    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?
    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?
  9. Dec 30, 2003 #8
    So the "ideal human" will be named Cletus?
  10. Dec 30, 2003 #9

    I was thinking maybe Jim-Bob or Jebidiah.

    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.
    (I am not planning on using this in the book, but let me just take it as an example...)
    Let's use the Biblical Adam and Eve.
    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?
    Last edited: Dec 30, 2003
  11. Dec 31, 2003 #10
    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?
  12. Dec 31, 2003 #11


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    Stop Mutation? Why?

    But don't you know that as a species, mutation is our friend? Metazoans evolved sex (and I think death too) to boost their Darwinian variation rate up so they could compete with the fast-evolving bacteria and viruses that attack them. There was a good book about this called The Red Queen's Race. And just as in that race in Through the Looking-glass you have to keep running (genitically varying) to stay in the same place. If you stop, the germs win!

    Sure, a lot of mutations kill or cripple their hosts, that's the down side of evolution; those mutations will be eliminated from future gene pools. But the ability to mutate is the ability to keep up with ever-changing nature.
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