Mother and son in New Mexico face jail time for incestuous relationship

[Thumpalumpacus]

No doubt -- laws aren't preventative, they're punitive. And I think you and I would agree that even if such a law did prevent these things, it still isn't the government's place to regulate this sort of thing; as others have pointed out, the gov't doesn't regulate other unions likely to produce birth defects.

But -- when I see the term "far more likely", I like to calibrate that judgement for myself. I know the logo behind the argument, but I want to see data that supports it.

So I poked around the internet for a bit and found a lone czech study on incest that shows that 1st degree incest (siblings or parent/child) results in almost 50% of children having a mental or physical deformity.

A group of genetic counselors reviewed the research on the biological consequences of sex between relatives (consanguineous relationships) (here). They found a surprisingly small increase (about 4 percent) in birth defects among the children of married cousins. Incest between first degree relatives, however, was a different story. The researchers examined four studies (including the Czech research) on the effects of first degree incest on the health of the offspring. Forty percent of the children were born with either autosomal recessive disorders, congenital physical malformations, or severe intellectual deficits. And another 14 percent of them had mild mental disabilities. In short, the odds that a newborn child who is the product of brother-sister or father-daughter incest will suffer an early death, a severe birth defect or some mental deficiently approaches 50 percent.

https://www.psychologytoday.com/blog/ani...lem-incest


Some of that is probably the result of generational incest though. So it's hard to say exactly what a lone case of incest like this one will do to a child. However I think you could still justify the law because of what groups or families of people could do, rather then individuals. A church group, say something like the Westboro baptist church or fundamentalist Mormons, could legally have incestuous relationships that fuck up generations of children if incest laws were repealed.  I'm not really sure personally how I feel about the law, other then incest is gross to the max. However I do see more to the law then just enforcing our inherent gross out factor on consenting adults.

I appreciate your detailed reply and the work which went into it. If their premises are sound, it would sure make a strong case for a law. But there's a couple of category errors built into that blog: on the one hand, it groups birth defects and "early deaths" together without defining the cause of early death, and on the other, it compares this conflated rate of defects and deaths to a 7% rate of defects-only, without mentioning early death at all in the control group:

of a study of Czechoslovakian children whose fathers were first degree relatives. Fewer than half of the children who were the product of incestuous unions were completely healthy. Forty-two percent of them were born with severe birth defects or suffered early death and another 11 percent were mildly mentally impaired. This study is particularly instructive as it included a unique control group — the offspring of the same mothers but whose fathers were not the mothers’ relatives. When the same women were impregnated by a non-relative, only 7 percent of their children were born with a birth defect (Figure 1).

Reading the supporting study, though, I'm certainly rethinking my position here.

I still don't think it's the government's business to regulate such interactions, especially if biology has already addressed the problem.