Believe it or not, but I was talking about this with a friend the other day:Researchers at the deCODE Genetics company in Iceland combed through more than 150 years of data and found that "kissing cousins" produce more children and grandchildren than unrelated couples:For women born between 1925 and 1949, with mates related at the degree of third cousins, the average number of children and grandchildren were 3.27 and 6.64, compared with 2.45 and 4.86 for those with mates who were eighth cousins, or more distantly related.
"These are counterintuitive, almost dislikable results," said Dr. Kari Stefansson, senior author of the paper on the study.
Dislikable, because our intuition is that the more closely related you are to your mate, the higher the chances of passing along the unfortunate traits so often associated with inbreeding.
Scientists are surmising that marrying your third cousin may actually be the best biological strategy for reproduction:
Link | Scientific American article - via 3quarksdailyNow, many gene experts are scratching their heads while trying to explain the biological mechanism behind these results.
According to Stefansson, the reason that related couples were more biologically successful may be because these couples have "just right" genes when combined — not too similar, but not too dissimilar, either. […]
"The take-home message is that … we, as a society of [the] 21st century, have basically ruled against the marriages of closely related couples, because we do not look at it as desirable that closely related people have children," Stefansson said. "But in spite of the fact that bringing together two alleles of a recessive trait may be bad, there is clearly some biological wisdom in the union of relatively closely related people."
Couldn't there be a non-genetic explanation for this as well? It seems like if you know your third cousin well enough to marry him or her, you probably have a tight-knit family that would provide support (and pressure?) for raising kids and bringing the couple together. It also seems like it would tend to happen where people have a greater likelihood of geographical proximity to extended family, implying less social mobility and therefore lower levels of wealth. Poorer people tend to get married at younger ages and have more kids.
All of these explanations seem to be consistent with the data and help explain the higher birth rates. If correct, it seems like these positive social benefits outweigh the potential biological negatives stemming from closer genetic patterns.
1 comment:
This debate underlines a big fear I have with American society. From its roots in Christianity, the move to a secular system may have left the state without a moral compass. Slate makes the point that if cousin marriages are allowed, the next move would be to incest(http://www.slate.com/id/2064227/).
This wouldn't happen with a theocratic system, because then you could look directly at what your religion says about the matter. Islam is clear that cousin marriages are halal.
As for the broader topic, I'd suggest looking at Straight Dope (http://www.straightdope.com/columns/041001.html) , although they make the potentially confusing point that 'Islamic cultures' prefer first-cousin marriages. Islam makes absolutely no such recommendation.
Also, I read somewhere that these restrictions precede modern genetics, so there might be other reasons for encouraging them. Here's an interesting thesis (http://www.press.uillinois.edu/books/catalog/76rws4ss9780252065408.html)
And finally, here's a good analysis from the law perspective (http://archives.cnn.com/2002/LAW/04/columns/fl.grossman.incest.04.09/)
Muslims, I think, would likely call it a 'draw': there's no harm/taboo/etc. marrying your cousin, first, second or third. On the other hand, there's a great benefit from marrying someone not related to you: you get to double the size of your family with your vows.
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