January 7, 2015

Robin Hanson
James M. Buchanan Center
Carow Hall
George Mason University
Farifax, VA 22030-4444
703 993 4854

Dear Professor:
The very impressive blogger “HBDchick” recently posted a map showing the distribution of cousin marriages in France over a number of years.  I was trying to google up a comparable map of fertility in France at the same time when I ran across your article about the early fall in fertility in France.  (http://www.overcomingbias.com/2013/05/french-fertility-fall.html) The piece is well done, but omits some science.  The brutal fact is that the fertility of a couple is determined by their kinship and that of their parents and grandparents back 9 generations and by nothing else. 

Such an unexpected claim, I’m sorry to say, rather puts you on the spot.  If I am kidding, it has to be the world’s strangest prank and healthy curiosity demands you find out.  If I am wrong, and you can prove me wrong with evidence, then your civic duty is to drop me a note making my error clear so I can stop spending my declining days trying to get people to notice.  And if I am right, it is the most important fact you will ever learn.  After all, what people do has a lot to do with who gets born. 

I have a 40 page literature review of everything I can find that bears on the case, but I can pare it down to just three papers.  The first is a summary of something like 1,700 serial field counts of wild animals and using that data relating population growth rate with population size. 

What they find is this:

Drawn from Sibly, R; Barker, D.; Denham, M. C.; Hone, J.; Pagel, M., On the Regulation of Populations of Mammals, Birds, Fish and Insects Science 2005, 309, 607-610.
Essentially the same curve has been demonstrated in humans both with children and grandchildren.  Helgason, A; Pálsson; SGudbjartsson, D. F.; Kristjánsson, T.; Stefánsson, K, An Association between Kinship and Fertility of Human Couples Science 2008, 329, 813 – 816.
Two papers published about fertility in Denmark Labouriau, R.; Amorim, A., Human Fertility Increases with Marital Radius Genetics 2008 178, 601-3. Labouriau, R.; and Amorim, A., Comment on “An Association between Kinship and Fertility of Human Couples” Science 2008 322, 1634b. Again demonstrate the same curve and this time they explicitly looked at wealth and education; when issues of marital radius and town size are accounted for (obviously both reflecting ancestral diversity) neither income nor education has any effect on the number of children a couple will have. 
(In other words the reason that the birth rate of countries where women have more education is low is not the education; it is the fact of going off to school, where they meet more young who are not sufficiently near cousins.)

Now you have been told.  Spend a few minutes looking up the articles and you will know beyond a shadow of a doubt.  And nothing could possibly be more important.  I’d be happy to send that review article.  Here’s a link to my most recent summary of the bulk of the evidence I have found.  http://www.nobabies.net/A%20January%20summary%20for%202015.htmlBut all you really need are the Sibly and Helgason articles. 

If it’s so important and so available why doesn’t anybody know?  Over the years I have written almost 200 experts inviting criticism.  Go to nobabies.net and look at the home page.  Maybe you know some of them.  The answer rate is less than 1%. 

So I can only complement you on your successful blog with its genial flow of comment. 

Admittedly I am telling people what they do not want to hear: “Keep your pants on in public,” or words to that effect.  Sex is a family affair.  You say people are rendered more receptive if they think what they are reading is “artistic.” 

HEAR, O ISRAEL:  The LORD our GOD is ONE LORD and thou shalt LOVE the LORD thy GOD with all thine heart, and with all thy soul and with all thy might … do you suppose he means sex?  Really?  And when he goes on and says that if you consort with other gods the Lord will wipe you from the face of the earth he couldn’t be talking about marriage could he?   Besides they didn’t have Modern Science so they were ignorant and stupid, right?  They would have had to have collected genealogies for centuries and then analyzed them and there is absolutely no interest in genealogies … oops … wait …     

I guess it’s safe to expect that if some of the most powerful language ever recorded didn’t persuade people that my own pathetic prose won’t either.

So have a look at the article.  Prove me wrong.  Pillory me in public.  Boldly go where no other expert has dared to tread: give an opinion.

I really do like your blog.


M. Linton Herbert MD

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