Re: Do arranged marriages tend to lead to endogamous relationships and reduce genetic diversity?

Mujin wrote:
In article <1165203004.404663.249440@xxxxxxxxxxxxxxxxxxxxxxxxxxx>,
edwinhere@xxxxxxxxx says...

Do you have specific examples of endogamous societies in which
genetic disorders (diabetes is not necessarily one - it can be
caused by a number of things) are more common than would otherwise
be the case? It's usually helpful to talk about concrete cases.

I have specific examples of genetic disorders like Becker's Muscular
dystrophy, Color Blindness in Family A and Family B with a lot of prior
marital relations between them. But they cannot be classified as a
general phenomena because I have not surveyed other families to check
whether there is an increased prevalence of such diseases in such
societies. The only well documented examples of endogamy leading to
diseases I have are the British Royal Family. But even they have
stopped practicing endogamy and now choose to marry commoners.

BTW, India; which practices arranged marriages has the largest number
of Diabetes mellitus type 2 patients in the world, more than China with
a larger population. Although environmental factors like high-carb diet
can be blamed for this, it is a well known fact that many Type 2
patients have a predisposition for this disease due to a non-Mendelian
polygenic inheritance.

As a general response, I would tend to suggest that whether the
society is endogamous or exogamous is unlikely to play a large role
in the fixation of deleterious traits in the population. More
important will be the size of the population from which a spouse is
to be chosen.

Endogamy & Exogamy is also defined by "the size of the population from
which a spouse is to be chosen". That is why I thought the role of
endogamy or exogamy is likely to play "a large role in the fixation of
deleterious traits in the population."

You may be noticing an artifact of the fact that most
modern endogamous societies are also of limited size. This has been
the case in most societies until quite recently, owing to the
difficulties involved in travelling any great distance.

"most societies were endogamous till recent times due to geographical
seperation" is debatable. One proof for the fact that people did travel
great distances to get to the next village is that, there are only a
few languages in use over large regions like Russia, China which shows
that people were in contact. But some other societies (which happen to
be endogamous) have a large number of languages showing that they were
not in contact and chose to procreate among themselves.

Now, an arranged marriage could well take place between people raised on
different continents.

What I find in arranged marriages that take place between continents,
is that they are not exogamous enough because the parents tend to
choose someone with the same genetic origins. Had there been no
arranged marriages people would have chosen healthier spouses using
natural ways of assessment which is more reliable according to research
findings of recent times.

The other issue is the question of what counts as endogamy - i.e.
where the line is drawn between in-group and out-group. This is of
course entirely arbitrary, and varies from society to society such
that what is technically considered endogamy may, genetically
speaking, effectively be exogamy.

Yes, the lines are blur. But it is a lot better to be on the safe side
by marrying the least genetically similar person who is willing to be
the spouse.

Take the example of a man
obligated to marry within his clan in a society where clans are a
matter of ritual membership, not biological relatedness.

There were times when rituals & traditions required people to sacrifice
their children if they want to be part of the society. Such practices
do not exist anymore. People did not change overnight. The first people
who tried to make a change got excommunicated. But that fear did not
stop them from choosing the altruistic option.

.

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