It has long been known that incest is not as bad as you think. Anti-cousin marriage laws are like prohibition laws and blue laws. They arise from a Christian conservative movement that swept Western Civilization from the late 18th century through the 19th century, up to about the time of the repeal of Prohibition.
Sure, marrying, or just plain having sex with, your sibling is disgusting. I mean, think about it. No, wait, don't even think about it. But cousin marriage? That depends. Your cousin may be kinda cute, you never know.
(a repost)
But seriously, anthropologists have long known of ... and have had two distinctly different explanations for ... patterns of marriage that involve linking up various kinds of cousins. At this point, let's just say that cousin marriage tends to benefit ... in terms of coalition formation, power management, and with respect to inclusive fitness .... the ascending (older, in charge) generation, even if it is no necessarily ideal for the marrying generation. This may well explain the pattern that we see: Prescribed cousin marriage is common in many scieties, but the degree to which it happens is at least somewhat correlated, it would seem, with he level of patriarchy. The more control older typically male power brokers have over things, the more people stick with cousin marriage. The less such power, the more rule breaking we see.
Forbidding laws are foreboding things. If you make a law that says that some behavior should never, ever happen, then people may become more fearful of the outcome of such actions. Cousin marriage laws instituted mainly during the last half of the 19th century have led to the general understanding that if cousin have a baby, it will have two heads. But in fact, and this has been known scientifically for decades, the increased rate of revelation of hidden recessive mutations in marrying cousins is small. It is about the same as a woman over 35 or so having a child.
A paper just out in PLoS Biology reviews the history of cousin marriage, its prohibition and the related controersy, in the West.
The conclusion is the following interesting conundrum:
...we note that laws barring cousin marriage use coercive means to achieve a public purpose and thus would seem to qualify as eugenics even by the most restrictive of definitions. That they were a form of eugenics would once have been taken for granted. Thus J.B.S. Haldane argued that discouraging or prohibiting cousin marriage would appreciably reduce the incidence of a number of serious recessive conditions, and he explicitly characterized measures to do so as acceptable forms of eugenics .... But Haldane wrote before eugenics itself became stigmatized. Today, the term is generally reserved for practices we intend to disparage. That laws against cousin marriage are generally approved when they are thought about at all helps explain why they are seemingly exempt from that derogatory label.
It is obviously illogical to condemn eugenics and at the same time favor laws that prevent cousins from marrying. ...
Interesting, that link between religious belief and eugenics.
As a paper published in an Open Access journal, you can review it yourself. Do read this paper, it is well done and quite accessible.
Diane B. Paul, Hamish G. Spencer (2008). "It's Ok, We're Not Cousins by Blood": The Cousin Marriage Controversy in Historical Perspective PLoS Biology, 6 (12) DOI: 10.1371/journal.pbio.0060320
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My brother married his first cousin. The father of the bride, and of the groom, are full brothers. So there was no need to worry about changing surnames either.
When they first figured out that their attraction was romantic, they looked into this -- and got exactly the answer you give. Absent a history of inbreeding, any additional risk from a first cousin marriage is small. They also checked legalities, and it's no problem here in in Australia.
They've now been married over twenty years, and have two daughters. It's tough for a proud uncle to be objective, but in all seriousness the kids are terrific. Well adjusted, smart, and a delight to anyone who who has dealing with them in any context. The additional closeness of the extended family give a definite added dimension, and we are all prodigiously proud of them.
I can imagine it would be awkward if a cousin marriage failed; but our extended family's experience of this relationship has been a wholly positive all the way down the line.
Thanks for the story.
I can imagine it would be awkward if a cousin marriage failed;
In fact, cousin marriages are often found to occur at higher rates not just in societies where they are allowed, but prescribed, and where divorce is not allowed or at least not easy. (This is based on somewhat subjective interpretation of well sampled cross cultural data).
It is also often the case that in situations such as this (which were very common, for instance, in 19th century Massachusetts) that land ownership gets intertwined right away. So a divorce may end up involving a real estate lawyer and possibly even the dreaded Commercial Real Estate Lawyer....
A question, if I may: Greg, you wrote "They arise from a Christian conservative movement that swept Western Civilization from the late 18th century through the 19th century"
and I agree that had a huge role in the idea - no argument. I've wondered, though, if another reason for this push was an attempt to increase the chances that new generations would be able to move up in society: children of lower-class families, marrying members of the same family, might not have the same options they would if they were to "expand their horizons", so to speak.
How ridiculous a thought is this?
Dean: Not ridiculous, but I don't think it is correct. You can see these laws forming up in the debates, on record in various ways, and there is a movement as described dealing with just about everything from dancing to drinking to marriage. The activists were not giving a lot of indication that they were thinking about democratization of opportunity.
Thanks for your time and answer Greg.
Regardless of its validity*, doesn't the argument that 'laws barring cousin marriage use coercive means to achieve a public purpose and thus would seem to qualify as eugenics' apply equally to laws governing any familial marriage, including mother-son, sibling-sibling, etc?
*To me the most immediately obvious potential issues are the scope of 'eugenics' and 'public purpose' and the sufficiency of the latter for the definition of the former...
Funny but I just ran into a woman with a ton of problems last week. She actually said to me that the source of the problems was "in-breeding."
Two first cousins had married and their off-spring, including her mother, had various physical defects. She herself had spinal nerve problems for which she had recently had major surgery. She showed me her long scar up her back and talked of other problems she and members of her family had. Her mother was born without a hip. She was born with an in-turned foot and scoliosis.
I was in shock that she admitted this all so freely. There were other people around in this store. She was angry about it all I guess and felt that others should be warned about what she referred to as "southern in-breeding."
I'm sure it doesn't happen all the time but it sure did in this family.
When I was in junior high, I had a school assignment to make a family tree. I had a very useful resource for this; some geneaology enthusiast who had traced their ancestors back to a 17th-century German immigrant had then traced back down the chain to find that person's descendants, put the whole thing into book form, and marketed it to the living members of that group. My grandparents (my maternal grandmother was one of said descendants) had purchased a copy, so I had the opportunity to get a big posterboard and sketch out my family tree back some fifteen generations. Cool!
So, I'm at my grandparents' house doing my research for that, but I hit a confusing bit. Some back-and-forth between the branches verified the source of my problem--two of my great-great-grandparents were first cousins. I started to ask my mother about this, but she shushed me. "Grandma's in the next room," she said, "and she doesn't like to talk about that."
As far as I can tell, there are no health repercussions showing up in my family from this. If you're thinking about marrying a cousin, though, I do need to warn you: it will make for a major pain in the ass for your great-nth grandchildren when they're drawing a family tree for a school project. Seriously. That relationship's so damn hard to draw. :)
One set of my great grandparents were first cousins (though they later divorced). My grandmother and several of her siblings lived well into their 80s.
If you want complications in the family tree try for a double first cousin marriage (not in my direct ancestral line, two sisters married two brothers and two of the children married [they had no children], then there was the third sister whose daughter married her first cousin and had an affair with her husband's [but not her] first cousin [and did have children but by which father?]).
For an exercise in drawing family trees, try out Abraham's family tree, based on information from the first half of Genesis. I used to use this in a computing class for a hard test case in data structures to represent relationships.
The most convoluted example is from Genesis 19; a story probably told by the ancient Israelites as a way of insulting nearby tribes of the Ammonites and the Moabites.
Lot (Abraham's nephew) escaped from the destruction of Sodom and Gomorrah with his two daughters. No other men were available, so the daughters decided to have children by their father Lot. They both bore sons to their own father -- who were designated as the ancestors of the Ammonites and the Moabites respectively.
The two boys are thus brothers. (Same father). They are also cousins. (Their mothers are sisters). Each is also the uncle and the nephew of the other. (The two mothers are their sisters as well, and hence children are nephews).
I have used this and similar stories as well in a teaching context. Given each son, calculate r.
So might your sister.....
*ducks*
There was an interesting case at work.
Jane married Mike, they had a daughter, they divorced all within 1 yeara.
Within a year Jane married Frank (Mike's brother), and they had a daughter.
The daughters are cousins and half sisters and about 3 years apart.
Cousin marriage might be legal or illegal is not the factor, the longevity is fragile and it hampers your family relation as well. You should not marry anyone of your family member to avoid the long term family trouble.