Patrick and Susan Stubing: Incest

This story over the brother and sister, Patrick and Susan Stubing. There's something that I haven't yet seen in the commentary upon it which rather helps to explain what's going on:

How could they not have been moved? Patrick and Susan want to be together but the state wants them apart and is intent on destroying their family. It has taken their three older children into care and the fourth may yet follow. Patrick has served two prison terms for "love" and another jail sentence threatens if Germany's highest tribunal, the Constitutional Court, refuses to legalise their relationship next month.
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Born into a violent and dysfunctional family of eight children, Patrick, now 30, was taken into care aged three or four, after being attacked by his father. He was later adopted. By the time he tracked down his birth mother in 2000, she was suffering from heart disease and being looked after by 16-year-old Susan. Their birth father was dead, as were five other brothers and sisters, some of whom were mentally handicapped, and all of whom died in childhood.

The couple say their sexual relationship began six months later, after their mother had died. In October 2001, Susan gave birth to a son, who was taken into care, as were two daughters who followed. Two of these three children are said to have developmental problems, although the severity is disputed. The authorities allowed Susan to keep a third daughter by Patrick because he was, by then, serving his second prison sentence for "illegal coitus". To complicate matters further, there is said to be a fifth child. Susan gave birth to another daughter by a 49-year-old "boyfriend" while her brother was in prison.

Now put aside the "instinctive revulsion" for a moment and consider the genetics for a moment. We are in general programmed to find those who are genetically close to us sexually attractive. Logically sensible, that we'd find those of the same tribe or group more attractive than those of others. (Those who find those around them shaggable will likely outbreed those who only find those from other groups so, given the way in which for most of our history as a species, contact with such other groups was rare.)

However, there are real problems when we are sexually attracted to those too genetically close to us, like siblings, those problems showing up in the next generation when recessive genes (I think I've got that bit right?) start to kick in.

So, in order for us to have got this far, without breeding the race into imbecility (in so far as this is not already true)  generations ago, there must be some mechanism by which this sexual attraction to those very close genetically can be turned off. Now this is only something I've seen around, can't even find the quotes, but it seems that this is nurture at work.

The attraction to those genetically close is nature at work, but turning that off is nurture: it's the very process of being raised together as siblings that turns off those feelings. I've seen a recent discussion saying that it's watching the mother caring for the other that does it. Anecdotally, and an older story, is that those children raised communally on kibbutzes do not mate amongst those they were raised with, whether they are genetically linked or not.

Now I agree that that's all a bit wishy washy, some half remembered stuff which not doubt an expert could clarify. But it does help us to explain what has happened here. As the children were raised apart, that nurture aspect didn't take.  There is therefore nothing there to overcome the nature part of the attraction to those genetically similar.

There's also a test that could be done, some research to see whether the general line of thought is actually correct. What is the general rate of incest amongst the population? And what is the general rate amongst children taken into care or adopted, rasied separately, and then meet again as adults?

Anyone know?