incest

Allen Smith allens at yang.earlham.edu
Thu Apr 9 00:58:10 EST 1992


In article <1992Apr6.151556.16781 at yang.earlham.edu>, allens at yang.earlham.edu (Al
   len Smith) writes:
> In article <1992Apr03.091936.11548 at deeptht.santa-cruz.ca.us>, rstevew at deeptht.
   santa-cruz.ca.us (Richard Steven Walz) writes:
>> In article <bruce.701664143 at harry> bruce at harry.ugcs.caltech.edu (Bruce J Bell
   ) writes:
>>>rstevew at deeptht.santa-cruz.ca.us (Richard Steven Walz) writes:
>>>
>>>
>>>[...]
>>>
>>>>I think that the various tribes of the world and the various ruling
>>>>monarchies in history and the same genetics which apply to breeders of
>>>>improved animals will tell you that incest won't really hurt a breed
>>>>of animals or humans unless you happen on a gene which has a delayed
>>>>effect during the life of the animal and you duplicate them through
>>>>enforced interbreeding, like the Pharoahs and the European Royalty.
>>>
>>>The reason inbreeding won't likely hurt a well-defined breed of domestic
>>>animals is that all such breeds are *already* extremely inbred, so
>>>that all the deadly/disease-causing recessives have been bred out.
>>>The inbreeding causes each animal to have identical copies of every
>>>gene, so that the results of mating within the breed is predictable.
>>>
>>>Humans, on the other hand, are genetically "wild", with thousands of
>>>harmful recessives, most of which are extremely rare.  However, incest
>>>makes it much more likely for these recessives to be expressed.  Thus,
>>>a product of incest is likely to have *extreme* genetic problems.  If
>>>a group of humans is willing to ignore the incest taboo and sacrifice
>>>a few generations of their offspring, they might be able to produce a
>>>breed of humans which could commit incest with impunity, but I don't
>>>think that is particularly likely, or particularly desirable...
>>>
>>>BTW, I believe some wild species have undergone population crises so
>>>extreme as to have a similar effect to human breeding.  Cheetahs are
>>>almost genetically identical to each other, so inbreeding doesn't have
>>>as severe an effect on them as many other species.  (I vaguely remember
>>>this from a Scientific American way back in the misty past, so don't
>>>count on this; look it up instead).
>
>       As I recall, Cheetahs may not have much impact from further
> inbreeding since they're already rather inbreed (it appears that there was
> a genetic bottleneck a bit back, and transplants from one cheetah to
> another, for instance, will not be rejected). BTW, I am not sure if this
> applies to all cheetahs, or just one population of them. Cheetahs have
> rather high sterility, miscarriage, and infant mortality rates due to
> genetic disorders.
>>>
>>>At any rate, there was, and is still, a very good reason to avoid incest.
>>>Don't knock the primitives until you have a very good handle on your facts...
>>>
>>>
>>
>> Bruce:
>> These aren't my facts. They are from a project paper I did one time on
>> the incest taboo in anthropology. I discovered that numerous
>> geneticists had been trying for years to get the ear of the amateur
>> geneticists out there who have been giving us the wrong ideas about
>> the "dangers" of incest. The quote from a group of them went something
>> like: Humans would have to enforce inbreeding every generation to
>> really get into trouble. Humans could in-breed every other generation
>> as an average without getting into trouble. Also. We share so many
>> genes which are fatal to the fetus when duplicated that only our level
>> of miscarriages might rise very slightly over the current level, and a
>> living duplication which was bad would be fairly rare. However,
>> enforced in-breeding would make the problem go exponentially critical
>> unless your family was free of survivable genetic disease. Please,
>> you look up your facts and get a handle on them. I already have. -
>
>       I don't doubt what you say, but I'd be interested in seeing the
> original papers on the subject. I can see humans having problems w/incest
> because of our habit of preserving and allowing to breed (in the case of
> royal families, encouraging) those with genetic defects. One could make an
> argument for eugenics, but fortunately germ line gene therapy (my intended
> field) is emerging as an alternative.

        BTW, I consider (as I forgot to mention in the original post) gene
therapy as a considerably more ethical solution than forced eugenics.
        -Allen
P.S. I wouldn't be posting this followup for this little added info, but I
forgot bionet.general the first time.



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