Saturday 20 March 2010

Today's facts and logic fail

From The Times:

Between 20 and 50 per cent of all Muslim marriages are said to be consanguineous [the PC term for inbreeding or even incest] and 8.5 per cent of all births are to parents related by blood [so that's an epic fail within the same sentence, unless the vast majority of consanguineous Muslim marriages are childless, whatever].

Religions vary as to what they allow. The Koran prohibits uncle-niece marriages, even though these are permitted by Jews and Hindus. Yet uncle-niece marrages involve the same amount of inbreeding as marriages between cousins — with 12.5 per cent of genes being identical.


Nope. We can argue the toss about the 12.5% figure, but an uncle-niece baby is far more inbred than one born to first cousins. The following diagram shows why:
To explain, in the top half, A and B have child AB, C and D have two children CD and CD; E and F have child EF. AB marries one of the CDs and the other CD marries EF, and so on. The two first cousins ABCD and CDEF have a baby ABDCCDEF. So that baby's genes are 25% from A or B; 50% from C or D and 25% from E or F.

In the bottom half, Uncle CD and Niece ABCD have a baby. Their baby's genes are 25% from A or B and 75% from C or D. That is a considerably smaller gene pool than a baby born to first cousins.

10 comments:

dearieme said...

The diagrams explain all; the words are unnecessary.

Mark Wadsworth said...

D, ta, I just wanted to explain it properly (in case I'm wrong).

Nigel Sedgwick said...

Well spotted Mark; the Times is being sloppy again.

In addition, the claim in the linked article that Victoria and Albert's cousin marriage made worse the risk of haemophilia of their children strikes me (having just checked Wikipedia: http://en.wikipedia.org/wiki/Haemophilia#Genetics ) to be wrong.

If Albert carried the gene, he would (like all male carriers) have been a sufferer. It looks most likely that Victoria carried the gene on one of her two X chromosomes only, as she was not a sufferer. Thus there would be a 50% chance of male offspring suffering and a 50% chance of female offspring being carriers, but not suffering (or only mildly due to lyonisation - inactivation of the good X chromosome).

So the Times was sloppy on that too; how sad.

Best regards

bayard said...

Is that really true about Jews and Hindus? I was under the opinion that Hindus took a very tough line on inbreeding, with marriage prohibited with anyone more closely related than fifth cousins. Hence the prevalence of arranged marriages, as everyone in a given village is likely to be too closely related to marry.

Mark Wadsworth said...

B, I would have thought so too, but I couldn't be bothered researching it. The whole article was full of holes, as we now know.

Paul said...

This is interesting. According to David Willetts in his book The Pinch (Grove Atlantic Press, 2010), I quote:

"In Pakistan 50 per cent of marriages are to first cousins. In Saudi Arabia this figure is 36 per cent."

Willetts to the quote from Emmanuel Todd, After the Empire. The Breakdown of American Order Colombia university press, 2003, p.50.

Now if I recall correctly, this chimes with my experience of Pakistanis in the UK who tend to call middle aged female acquantancies "Auntie". Not just because it is familiar but also because it is likely probabilistically, to be true.

Nick39 said...

One of the reasons why Europe is not under any threat from Islam - if we'd only stop commiting cultural suicide.

They are hardly breeding an army of super soldiers with lightning reasoning skills.

Mark Wadsworth said...

P, more holes in the article then.

K, true, but it doesn't require 'lightning reasoning skills' to be duped into becoming a suicide bomber.

Pogo said...

Mark, re your comment about "lightning reasoning skills" and "being duped" - one would have thought that the lack of skills is a prime requisite for being "persuaded"...

Mark Wadsworth said...

P, that's what I meant. According to the full article, about ten per cent of these inbred kids are mentally subnormal, that's a heck of a lot of potential suicide bombers.