"Gordon Hodgson"  wrote in message
news:b9ji56$2qc8$1{at}darwin.ediacara.org...
> In message , Srinivas S
>  writes
> >Why do some cultures allow marriage between close relatives and others
> >treat it with great contempt? The usual argument against inbreeding is
> >that rare genetic diseases can show up easily in a child which inherits
> >harmful recessive genes from both parents. Why is this not applicable to
> >those cultures which have been in existence for a long time and allow
> >inbreeding? There SEEMS to be apparently no observed phenomenon of high
> >incidence of genetic diseases in those communities.
>
> I don't know that that's true. What about Tay-Sachs disease in Ashkenazi
> Jews? I think there's an increase in cystic fibrosis or some other
> genetic respiratory disease as well. In fact, I've got a list in front
> of me, and I remember some form lectures, of isolated communities (as a
> result of stemming from a single founder, or religious reasons for
> inter-marriage) with common incidence of rare recessive disorders. Also
> mentioned are the Amish, some groups of Finns, Afrikaners, it's quite
> interesting really. I read in "genome," I think it was, that someone
> set-up a genetic counselling project for Hasidic Jews in America to
> determine whether couples were carriers for genetic disorders that were
> common to their ethnic group (tay-sachs, and the other disorder) and it
> had a considerable effect in reducing disease incidence.
>
> Why some cultures allow it? Hm. I guess it's a result of the behaviour
> of the cultural and genetic founder of that population. There was a
> Simpsons episode where Springfield and Shelbyville are founded with the
> same ideals except that in Shelbyville you were allowed to marry your
> cousin. I don't know if something similar happens in the non-satirical
> world when culture pockets are formed?
>
>  From what I gather, there is both inbreeding and outbreeding depression,
> although inbreeding depression seems more serious. Behaviour should
> evolve to go against things that are negative for the survival of the
> genome, I would think, but obviously there are people that do stupid
> things all the time. If the founder of a population, thought that
> inbreeding was a good thing, for selfish, or religious reasons, it might
> make sense that his descendants would agree, because they had the
> genetic predisposition to agree (just as the founder did) and they were
> taught by observation, and word of mouth that inbreeding in this
> situation was a good thing.
> -- 
> Gordon Hodgson
> (news)(at)(rockmuppet)(dot)(co)(dot)(uk)
>
> http://www.jubileedebtcampaign.org.uk/ is not a debt consolidation site
> Guess what, neither is http://www.debtlinks.org/
>
> If you wish to reply, make sure to take out the rubbish
>
Some people marry relatives to keep money, power, and sacredness in the
family. Of course live stock breeders do it to get better live stock and you
might do it to get better humans but in order for it to work you just might
need to be willing to cull the rejects which some groups did normally as
infants or by running them through tests at puberty. Of course parents tend
to want to save their kids even if they have defects but if you have a lot
of kids you might be willing to let a few go, maybe. An alternative to
culling rejects is selecting the "most fit" and sort of egnoring the the
rejects. I'm not sure if that's really been done with humans.
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