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Konkvistador comments on Poly marriage? - Less Wrong

-9 Post author: h-H 06 June 2012 07:57PM

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Comment author: Konkvistador 07 June 2012 06:00:27PM *  7 points [-]

I think laws forbidding cousin marriage are unfair and should be the next target of civil rights activism. Incest laws in general makes no sense except as a eugenics measure. Either we dump these laws or we judge all eugenic measures that rise above it in the cost-benefit metric as acceptable. Else we are just picking and tormenting loving couples because of some historic baggage.

And where is the transhumanist spirit? Technology lets a brother and a sister have as healthy a baby as anyone else's.

Edit: Added the eugenic argument, I originally didn't think I would need to.

Comment author: gwern 07 June 2012 06:16:41PM 6 points [-]

Incest laws in general makes no sense.

I believe I've previously pointed out inbreeding depression to you; from Jensen 1969:

In Japan approximately 5% of all marriages are between cousins. Schull and Neel studied the offspring of marriages of first cousins, first cousins once removed, and second cousins. The parents were statistically matched with a control group of unrelated parents for age and socioeconomic factors. Children from the cousin marriages and the control children from unrelated parents (total N=2111) were given the Japanese version of the Wechsler Intelligence Scale for Children (WISC). The degree of consanguinity represented by the cousin marriages in this study had the effect of depressing WISC IQs by an average of 7.4%, making the mean of the inbred group nearly 8 IQ points lower than the mean of the control group. Assuming normal distributions of IQ, the effect is shown in Figure 9, and illustrates the point that the most drastic consequences of group mean differences are to be seen in the tails of the distributions. In the same study, a similar depressing effect was found for other polygenic characteristics such as several anthropometric and dental variables.

The mating of relatives closer than cousins can produce a markedly greater reduction in offspring's IQs. Lindzey (1967) has reported that almost half of a group of children born to so-called nuclear incest matings (brother-sister or father-daughter) could not be placed for adoption because of mental retardation and other severe defects which had a relatively low incidence among the offspring of unrelated parents who were matched with the incestuous parents in intelligence, socioeconomic status, age, weight, and stature.

No doubt one could dig up more recent results with a suitable search.

Comment author: Konkvistador 07 June 2012 06:23:10PM *  5 points [-]

Should we use eugenic reasons forbid the marriage of women over 40 planing on having babies as well? The defect rate in children is the same just so you know. In the Western world most people are pretty out-bred, one generation of inbreeding does very little damage and very few Westerners will choose to marry their cousins generation after generation.

Comment author: gwern 07 June 2012 06:29:25PM 11 points [-]

Should we use eugenic reasons forbid the marriage of women over 40 planing on having babies as well?

Yes. We should also encourage the use of sperm donors as resulting in 1/5 the birth defect rate. (On a large scale, this advantage would erode, but that is easily dealt with by encouraging men to donate more and treating them less like crap; we can think of it as 'sperm banking', akin to existing practice of 'egg banking'.)

In the Western world most people are pretty out-bred, one generation of inbreeding does very little damage

Do you know this, or are you guessing? If I were to go looking for any studies in out-bred populations, at how many points of average IQ damage would you concede the point?

Comment author: Konkvistador 07 June 2012 06:30:49PM *  4 points [-]

Yes. We should also encourage the use of sperm donors as resulting in 1/5 the birth defect rate.

Ok you win eugenics is a good idea. But after designer babies are the norm, this rationale becomes obsolete.

Comment author: [deleted] 07 June 2012 07:33:49PM *  1 point [-]

In the Western world most people are pretty out-bred

By “the Western world” you mean the Americas or some subset thereof? Because I doubt there's that much genetic diversity in, say, Iceland (and in Italy there are some small towns where one or two family names comprise the majority of the population).

Comment author: Konkvistador 08 June 2012 05:29:36AM *  3 points [-]

The Western world. You need to keep in mind that inbreeding is the human norm. Europe, at least any part that was under Catholic influence for a few centuries is a massive outlier in its low rates of consanguineous marriage.

Comment author: [deleted] 08 June 2012 07:37:51AM 2 points [-]

Europe, at least any part that was under Catholic influence for a few centuries is a massive outlier in its low rates of consanguineous marriage.

They might not marry close relatives (say, those with common ancestors from 200 years ago), but when it's customary to only marry people from your own town with a population of 1000, this means that lots of your ancestors from 500 years ago are your spouse's ancestors too, so you still share lots of genes.

Comment author: Konkvistador 08 June 2012 07:41:01AM *  2 points [-]

Urbanization in the 19th and 20th century mean this is very seldom still the case. How many people live in such small towns? And those who more often find spouses via work or in the course of their education, which seldom takes place in such small towns.

In any case the defect rates for such towns are only very seldom a problem. A better point in your favour might be the relative close relatedness of say the Aksenazi Jews.

Comment author: JGWeissman 07 June 2012 06:21:37PM 0 points [-]

The parents were statistically matched with a control group of unrelated parents for age and socioeconomic factors.

Do "socioeconomic factors" include the parents' IQ?

Comment author: gwern 07 June 2012 06:30:08PM 2 points [-]

Given the strong influence of IQ on socioeconomic status, even without controlling for IQ explicitly, there's still going to be substantial controlling for IQ that way.

Comment author: JGWeissman 07 June 2012 06:45:23PM 2 points [-]

That would not be enough control if IQ has influence on whether someone marries their cousin.

Comment author: gwern 07 June 2012 06:55:19PM 2 points [-]

Are you arguing for the sake of arguing a methodological point, or do you seriously think that this point has a >50% chance of making the theoretically predicted and empirically confirmed phenomenon of inbreeding depression just go away?

Comment author: JGWeissman 07 June 2012 07:11:24PM 2 points [-]

I don't think it makes the inbreeding effect go away completely, but it seems worth considering if there are other contributing factors to the observed effect. (Probability less than 50%, but I think worth tracking.)

I would be careful about dismissing "methodological points". The methodological standards are there for a reason.

Comment author: ArisKatsaris 08 June 2012 09:34:58AM 2 points [-]

I think laws forbidding cousin marriage are unfair and should be the next target of civil rights activism.

I've seen it argued somewhere that the acceptability of cousin marriage in society also relates significantly to the presence of corruption/nepotism/tribal thinking in that society.

Incest laws in general makes no sense except as a eugenics measure.

Besides eugenics issues, I'd guess that because of pre-existing power dynamics incest probably has much more of a potential to be psychologically unhealthy than most non-incestuous sexual relationships -- much like teacher-student / doctor-patient relationships are also frowned upon, except that the familial dependency is even stronger.

It puts all the eggs in one basket after all (psychological/financial support from biological family, psychological/financial support from significant other) -- if these are the same people, who do you turn to when you have problems?

Comment author: Eugine_Nier 09 June 2012 01:12:18AM 1 point [-]

I've seen it argued somewhere that the acceptability of cousin marriage in society also relates significantly to the presence of corruption/nepotism/tribal thinking in that society.

You mean hbdchick?

Comment author: [deleted] 07 June 2012 07:28:45PM *  1 point [-]

Did you edit in “except as a eugenics measure” after gwern's comment?

Comment author: Konkvistador 08 June 2012 05:25:06AM *  1 point [-]

Yes. Because I originally didn't think people here would need that explicitly argued against. I will make the edict explicit.