I was very surprised to see how many US states ban first cousin marriages. Why is that?

A lot of the states that have them were founded from the midpoint to the end of the U.S.‘s history. During that time, there was a lot of concern over ensuring healthy families and, unfortunately, a distinct eugenecist thread to it all (race mixing would lead to inferior races, etc.).

So…much of that ban was probably in place in order to ensure that inbreeding wouldn’t yield unsuitable child citizens (heredity study was fairly new), and was kept because no one is really stomping their feet in court to get that ban dropped.

@iamthemob – ‘stomping their feet?’, how many are we talking about here? :-) I actually have more that the average number of feet but I don’t talk about it much. At least I do have the median number of feet.

I think I may be the illegal offspring of a marriage between statisticians. Probably.

Enough feet to get the state legislature’s attention…

Having more than the expected number of feet might be what this law was trying to prevent.

Here’s an abstract of one study that mentions there are 35 distinct genetic diseases due to inbreeding. http://jmg.bmj.com/content/24/6/362.abstract

Outlawing first cousin marriages is actually excellent policy!

@snowberry – as @markferg points out, the instance of there being an instance of abnormality for cousin marriages is pretty low. The population that you point out is a small isolated one that has been engaging in long-term incestual practices – so there is an extremely, extremely limited gene pool.

The likelihood that a set of first cousins will marry, and then their offspring will marry their first cousins…and so on…and so on…is incredibly unlikely considering the mobility and size of the U.S. population. You do see it happening, but in very specific populations – the Amish, for instance.

I remember reading a long time ago about there being concern about family wealth and not necessarily about possible genetic issues. I can’t remember which family it was, but one very rich family would actually encourage cousins to marry in order to prevent the family wealth ever going to an outsider.

Edited: I just looked up the Du Pont family on a whim, and they were one of many rich families that arranged marriages between first cousins to keep their money in the family. I wish I could find what I read in the past about this being a specific problem for people relating to their money, but that was a long time ago.

And it’s just this sort of problem that the law is intended to resolve. Isolated populations DO still exist in the USA, believe it or not. I might also mention that children that are deformed as a result of interbreeding often become a drain on society (due to being disabled-down syndrome for example), which probably helped drive the law in the first place. If you are really determined to marry your first cousin or your sister for that matter, you can go where it’s legal to do so.

@snowberry – There’s no doubt that the law has been maintained because of those concerns. But still, it’s an unwarranted concern because the individual instance of problems is so low.

The problem, of course, is that we’re talking about marriage. Married people aren’t the only ones who reproduce, and if the state isn’t going to recognize a couple – well, they’re still going to be together unless it’s something criminal. Further, the isolated populations that you’re talking about in the U.S., if truly isolated, aren’t going to be able to reach outside their small group. Of course, that doesn’t meant that they’ll abstain from having the relations.

We are humans, not dogs. Dogs are sometimes inbred and this creates puppies with all sorts of physical and mental conditions.

This is the purpose of not marrying first cousins and the law.

@john65pennington – Seriously, again – dogs are inbred over generations and that’s the problem with pure breeds.

As stated above by @markferg, but to emphasize – in April 2002, the Journal of Genetic Counseling released a report which estimated the average risk of birth defects in a child born of first cousins at 1.7–2.8% over an average base risk for non-cousin couples of 3%, or about the same as that of any woman over age 40. In terms of mortality, a 1994 study found a mean excess pre-reproductive mortality rate of 4.4%,

But finally – reproduction is not an essential element of marriage. There are plenty of people young and old who get married with no or uncertain intentions about having children.

It just seems like a pointless regulation at this time in our history.

And again – cousins who want to have sex are gonna do it, regardless of the ick factor for some. Marriage doesn’t PREVENT those who don’t marry from reproducing.

Let’s just note that there are 20 states or so that allow first cousins to legally marry. Have we had rampant instances of first cousin married sex babies with developmental problems?

PS – I do not mean to sound confrontational on this one…I know you might simply be answering the OP’s initial question with your opinion about what the legislation was initially for.

Americans have always liked to try and legislate what we do sexually mostly in the name of god. Im not sure why anyone should care if I buttfuck my cousin but tellimg me I can’t isn’t freedom.

They have seen in the southern states the result of what happens if you DO marry your cousin….......... eeeeeeeeeeeeeeeeeeeeeeeeeeeek!! (I think that’s where George W came from)