June 19, 2015


Fareed Zakaria

Dear Fareed Zakaria:

I see you have taken an interest in the low birth rate in developed countries such as the program on CNN Sunday June 14, 2015 at 1:30 PM.  You point out that 1) Birth rates are unsustainably low in many rich countries and are falling elsewhere.  2) This could lead to serious problems. 3) Throwing money at people to get them to have more babies seldom if ever works.  That seems like little to say about such an obviously important subject, but until now there was little more too say. 

That has changed with the publication this year of Handbook on Evolution and Society eds. Jonathan H. Turner, Richard Machalek and Alexandra Maryanski by Paradigm Publishers, London and Boulder.  It is a textbook on sociology and should be available in libraries.  The relevant and exciting chapter is 19, by the renowned professor Robin Fox.  The title of the chapter goes straight to the point: “Marry in or Die Out.”  The point is that if we fail to marry fairly close kin, as humans have as long as we have married, and mated with kin before that, we shall not have the adequate birth rate we used to have.

I have read the chapter carefully and hasten to assure you that this has nothing to do with race or ethnicity.  The ideal couple for maximum fertility is about third or fourth cousin with a drop off for more distant kin.  Out past ninth cousin fertility is significantly depressed for two generations and then gets really bad in the next.  So except in rare cases ones viable choice of mate is a tiny sliver of ones ethnic group, and a member of a different ethnic group might be satisfactory so long as that person is a traceable cousin.

Of course this is thrilling news.  It offers a rational scientific approach to recovering a viable birth rate as an alternative to the rewards approach now proven to fail.  In the introduction the news from Professor Fox is, with editorial understatement, “Surprising.” 

In fact the professor carries it farther and demonstrates the effect in bacteria, but I shall leave the chapter to explain how that works.  Hitherto it has only been demonstrated in mammal, birds, fish and insects although it is clearly a general principle.

Since you already have an interest and actually know just about everything else one can readily learn about our low birth rate, I thought you would be interested.  Fox teaches at Rutgers so he will not be hard to find, and I am sure he would welcome any inquiry on your part for clarification or anything else.  Do feel free to contact me if I can help in any way (like if it’s difficult to find the book or the professor or anything you can think of). 

This will be an amazing intellectual journey for you.


Linton Herbert MD 

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