April 1, 2013
to be posted on Nobabies.net

Hillay Zmora
History Department
Ben-Gurion University of the Negev
P.O.B. 653 Beer-Sheva 8410501

Dear Hillay Zmora:
First let me beg your indulgence in writing you about a subject wherein you doubtless have little interest and I am unequipped to apply my thoughts to your own field.  There is a chance you may respond, “I’d wondered about something like that,” so I shall proceed.

Your book (Hillay Zmora The Feud in Early Modern Germany Cambridge University Press, Cambridge, 2011) is a splendid accomplishment of which you should be quite proud.  It was brought to my attention by a friendly blog http://hbdchick.wordpress.com/ which takes an interest in the interplay between mating strategy and social phenomena such as where one invests ones altruism. 

My own interest is in mating strategy and fertility so I was drawn to your fourth chapter “The wages of success: reproduction and the proliferation of conflicts.”   Let me introduce a “theory of everything” as regards history, both human history and natural history.  Pursuant of that let me define for the nonce “endogamy” and “exogamy.”  Generally they are taken to mean marrying (or mating for animals) inside or outside of some social group to which one belongs, and that social group can vary greatly in size.  For the purposes of this letter only I shall define endogamy as marrying sixth cousin or closer and exogamy as marrying tenth cousin or more distant.

The theory is: “Endogamy tends to persist over generations as some tight knit community confines its socialization to the village or band.  Exogamy tends to persist over generations as it is generally initiated by a move to a different country or from countryside to city where it is very unlikely that a descendent in the next few generations will ever meet anyone from the original endogamous group.  Endogamy produces high to adequate fertility indefinitely.  The first exogamous generation may see fertility on the order of eight offspring per couple.  The second generation may see four.  The third generation may expect two.  The fourth generation may see only one.  Beyond that the line is highly unlikely to survive.”

I am being more specific than I have any right to be.  That is for clarity.  Let me digress upon some problems with the theory as stated.  The numbers are very rough.  On current data in fact the fall from first to second generation is about the same as the fall from second to third.  From third to fourth is actually worse.  I’m sure somebody has useable numbers; no less an authority than The Economist magazine once remarked that immigration is not a long term solution to demographic decline as the fertility of immigrants falls to the level of the host country after a few generations.  They had to have numbers behind that, but alas did not reveal the source.  Another problem is that a first fourth generation urbanite might well marry a first generation urbanite.  I imagine the outcome would be some sort of average of their respective expectations but have no numbers.  The worst problem is that this very idea is so repugnant to most that it is dismissed out of hand without even considering the data.  If you would like to see my data it is summarized on http://nobabies.net/A%20December%20summary.html

Another issue is that if instead of a migration the shift from endogamy to exogamy occurs because of natural increase in the size of the original endogamous community.  In that case as the population declines endogamy my be restored and the birth rate rise again.  So far as I can tell it is not likely that the population can survive the second cycle, at least for mammals.  It can in insects.  The reason appears to be that while insects and mammals share a post-zygotic mechanism limiting gene pool size, mammals also have a pre-zygotic mechanism.  If you want further clarification of that, I was involved in a recently published paper about fruit flies.  (Fluctuation of fertility with number in a real insect population and a virtual population
M.L. Herbert & M.G. Lewis African Entomology 21(1): 119–125 (2013)) The purpose of that study was to see whether there might be something related to this that might be used against the mosquitoes that carry malaria. 

Ever hungry for data, I was reading your chapter about feuding and reproduction and sure enough some of the impetus for feuds was that there were more men in titled families than there was land to support them; they were undergoing natural increase.

That puzzled me.  Generally rich people go infertile.  For a man wealth is an advantage in attracting women.  But that is not the whole story to having children.  The very wealth that makes a man attractive tempts him toward exogamy. 

The most glaring exception is England.  (Britain if you like, but it goes back long before the United Kingdom)  Gregory Clark in A Farewell to Alms points out that the English wealthy class had a high birth rate, unlike most other rich folk.  He pointed out that this resulted in “downward social mobility,” resulting in people doing work for which they were overqualified and further resulting in the Industrial Revolution.  I think it also is why society there has gone more than nine hundred years without collapsing; as that web site with the summary I pointed out shows, this is most remarkable; societies generally collapse around their 300th birthday.  I credit their resilience to the fact that women have always been able to own land in England.  So one was eager, if one was a man with land, to marry a woman with land nearby so it could be managed at the same time, thus all unwittingly maintaining endogamy and fertility.

But if I remember Shakespeare’s “Henry V,” Salic Law stipulated that women could not hold land.  So that explanation did not work.  But then on page 96 you mention that endogamy was the order of the day. 

Suddenly I smell data.  The aristocrats kept track of their genealogy.  If what I am saying is true, it is true not only of the landed society as a whole, but of individual families.  You may have those records.  You may in fact already have done the analysis and then pushed it aside because it wasn’t what anybody else was saying and you didn’t know quite what to do with it. 

If that is true, then maybe you have not wasted your time reading this far. 

Let me know what you think.


M. Linton Herbert MD

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