Cousin marriage laws outdated

December 23, 2008

Laws banning marriage between first cousins are based on outdated assumptions about a high degree of genetic risk for offspring and should be repealed, according to a population genetics expert.

In an opinion article published in the US open-access journal PLoS Biology, University of Otago Department of Zoology Professor Hamish Spencer and Professor Diane Paul, a Research Associate at Harvard's Museum of Comparative Zoology, argue that laws against cousin marriage are ill-advised.

"Neither the scientific nor social assumptions behind such legislation stand up to close scrutiny," says Professor Spencer. For example, a 2002 expert review of studies regarding birth defects in offspring of cousins found that the risk was much smaller than generally assumed, he says.

The US National Society of Genetic Counselors (NSGC) report estimated the average risk as 1.7 - 2 per cent higher than the background population risk of congenital defects and 4.4 per cent higher than general risk for dying in childhood.

"Women over the age of 40 have a similar risk of having children with birth defects and no one is suggesting they should be prevented from reproducing. People with Huntington's Disease or other autosomal dominant disorders have a 50 per cent risk of transmitting the underlying genes to offspring and they are not barred either," Professor Spencer says.

In the USA, there are 31 state laws that either bar cousin marriage outright, or permit it only where the couple obtains genetic counseling or is beyond reproductive age or if one partner is sterile.

"Such legislation reflects outmoded prejudices about immigrants and the rural poor and relies on oversimplified views of heredity. There is no scientific grounding for it," Spencer adds.

The article can be viewed at http://biology.plosjournals.org/ .

Source: Public Library of Science


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  • thales - Dec 23, 2008
    • Rank: 4 / 5 (3)
    That's interesting, but the social stigma against it won't go away anytime soon.
  • General_Haberdashery - Dec 23, 2008
    • Rank: 4.8 / 5 (4)
    However cousins repeatedly breeding would lead to a high probability of defects within a few generations I'd think.
  • samlehmanwilzig - Dec 23, 2008
    • Rank: 5 / 5 (4)
    To continue the previous comment of G_H, the researchers should go to Northern Israel where cousin marriage is very widespread among Israeli Arabs. The incidence of serious birth defects cognitive impairment is so great that the Moslem leadership has begun to proselytize against te custom. The problem is not any two cousins marrying but the "culture of cousin marriage" that cumulatively leads to disastrous results. Further, the comparison with carriers of a Huntington's Disease gene is completely disingenuous -- THEY have no choice, as the genes are within them! The "cousins", on the other hand, have a huge choice of spouses that are not related to them.
  • daqman - Dec 23, 2008
    • Rank: 5 / 5 (4)
    Suppose I alone in a population of 10,000 marry my cousin and there is, for example, a 1 in 50 probability of a problem. That is 1 in 500,000 chance of a problem in the entire population. But if EVERYONE marries their cousin the probability is 1 in 50 for the entire population which is a BIG problem.

    These laws were invented (and make sense) when the population is small and stagnant so the probability of wanting to marry a cousin is high.
  • rubberman - Dec 24, 2008
    • Rank: 1 / 5 (2)
    It would if I had hot cousins....
  • CheapJeep - Dec 25, 2008
    • Rank: not rated yet
    There's two ways to look at this. The first being physical, property based (which is ridiculous in families of 6-8 children or more) conservation of wealth.
    The second is genetic. If you want to lock in allele patterning, fixing traits for intelligence and the like, marrying like to like will get you higher and higher means of baseline performance, just like a thoroughbred horse.
    The problem is that you then need to be cognizant of things like '4% of the mentally unfit create 33% of the next generation of same'.
    And either sterilize or kill those whose contribution to the gene pool is questionable to select them out, Darwin style.
    If you can't handle this Spartanesque approach, you will gain nothing but despair for your children or children's children and that this happens in places like Pakistan with it's microcephalic culture and generally inbred violence and poverty must be set against the reality of a 'global village' where countries like England not only are subject to inundation by high birth rate SWA communities rapidly threatening indigenous population at a economic level.
    But their inbred children are causing massive headaches for the socialized medical system.
    Overall, absent legalized GE for human traits, inbreeding is the only way to get towards highly evolved personality traits whose association is known-genetic (across several generations).
    If you have 2,000 years, you can follow the path of the Ashkenazi Jews and end up with nearly a full standard deviation in intellect advantagement over the entire world _on average_. Simply by controlling whom is allowed to breed with whom. 'Keeping it in the family' being the simplest way to assure that, irrespective of social more`s.
    At which point you are back to the practical economics of no longer talking about inheriting the family business. But having a stake in the wealth that decades if not centuries of IQ based social mobility have cumulatively made possible.
    Don't think that Old Money breeds entropic decay. It breeds more Money. For a reason.
  • Velanarris - Dec 30, 2008
    • Rank: 1 / 5 (1)
    If you have 2,000 years, you can follow the path of the Ashkenazi Jews and end up with nearly a full standard deviation in intellect advantagement


    What white power anti-semetic site did you pull that garbage from?

    80% of the world's Jews are Ashkenazim and they certainly don't have any sort of rabbinical law ordering them to marry cousins, nor are they classed as any more or less intelligent than everyone else.
  • samlehmanwilzig - Dec 31, 2008
    • Rank: not rated yet
    Velanarris:
    Right on the first count and wrong on the second. First, Rabbinic Law forbids marrying one's aunt, and traditionally the Jewish community has frowned on cousin marriages (although it did occur infrequently). On the other hand, every national IQ test of the past decades in the U.S. shows the Jewish cohort with a 116 IQ (tied with Asiatics) -- the highest of any group, and obviously significantly above the 100 median for the entire population. There are many possible reasons for this, some related to "cultural genetics" (how cultural predispositions might lead to genetic "improvement" or "decline"). For a wide-ranging discussion of the "Jewish genius" phenomenon I suggest reading Charles Murray's (he's a Gentile) very interesting article in Commentary Magazine from April or May 2007. The letters to the editor a month or two later are no less fascinating.
  • Velanarris - Jan 01, 2009
    • Rank: 1 / 5 (1)
    Velanarris:
    Right on the first count and wrong on the second. First, Rabbinic Law forbids marrying one's aunt, and traditionally the Jewish community has frowned on cousin marriages (although it did occur infrequently). On the other hand, every national IQ test of the past decades in the U.S. shows the Jewish cohort with a 116 IQ (tied with Asiatics) -- the highest of any group, and obviously significantly above the 100 median for the entire population. There are many possible reasons for this, some related to "cultural genetics" (how cultural predispositions might lead to genetic "improvement" or "decline"). For a wide-ranging discussion of the "Jewish genius" phenomenon I suggest reading Charles Murray's (he's a Gentile) very interesting article in Commentary Magazine from April or May 2007. The letters to the editor a month or two later are no less fascinating.


    If this is the case then why is the average IQ in Israel 90?

  • thales - Jan 05, 2009
    • Rank: not rated yet
    If this is the case then why is the average IQ in Israel 90?

    Source please?
  • Velanarris - Jan 05, 2009
    • Rank: 1 / 5 (1)
    http://www.google...ch?hl=en&q=israel average iq&aq=f&oq=

    pick one.

December 23, 2008 all stories

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