January 16, 2013
to be posted on nobabies.net

Robert Trivers
Anthro, Rutgers 
131 George St 
New Brunswick, NJ 08901-1414 

 (732) 947-8880 (will not be active until September)


Dear Professor Trivers:
I have read your book (Robert Trivers The Folly of Fools, Basic Books division of Penguin New York 2011), an emotional rollercoaster it took me a month to get through.  Many books seem to have only one idea, often completely explained by the title, but your ideas come thick clear.  Well done.  In fact I shall have trouble staying on topic.  I’ll offer a deal.  Respond to this letter in a form I can post on my web log and I shall give you three ideas your book elicits, each lest horrible than what I am about to delineate. 

There is a case of self deception that cries out for your able analysis.  This deception is a massive delusion altering a life or lives for the worse, untenable in the face of science and capable of causing incalculable social harm.  I shall let you decide just who is deluded.

Consider the question, “Suppose you want your life to be a biological success, that you want to have more than four grandchildren, and you have a choice of mates, two members of the opposite sex whom you like and both of whom seem excellent mates, come from a culture similar to your own and are indistinguishable except for one thing; one is your third cousin and the other unrelated at least out to tenth cousin.  Which is your better choice?”

In one corner I stand almost alone.  In the other corner is almost all of the developed world.  I say go for the third cousin and the others say resoundingly go for the unrelated one.

They have, of course, the consensus.  Genetic diversity is good.  You say so yourself on page 226 and return to the issue later.  I, on the other hand, have evidence. 


Or you can go to nobabies.net and look at the December 21, 2012 post.

You rightly point out that too much inbreeding is bad for the immune system.  If the major histocompatibility group complex is not diverse enough, the immune system suffers.  There is a best zone, something Patrick Bateson calls, “optimal outbreeding.”  So it is with fertility.

You point out in your book that in places with a high parasite load there are more religions per square mile (or as you put it per square inch) than in less burdened places and you rightly point out that shunning strangers is a way of shunning disease.  Religious divisions generally entrain mating divisions.  On the other hand my pet hate in terms of parasites is malaria, and the last time I checked mosquitoes were exemplary in their indifference to religious differences.  On the other hand as you rightly point out religious divisions promote consanguinity, and that of course generally raises fertility.  High parasite load probably (I don’t know the numbers, but the relevant statistics surely have been developed somewhere) correlates with fewer children reaching reproductive age so greater consanguinity might be vital for some populations. 

I hasten to point out that the infertility in any one population saturates at about seventh cousin.  Past that it does not matter whom you marry.  The problem is when the program of outbreeding goes on generation after generation.  You refer to the common belief that the ills of inbreeding accumulated over generations.  Of course you can overdo it.  As far as causing homozygosity of deleterious genes, that ought to decrease as such genes are expressed and eliminated so a different mechanism must be found.  The ills of outbreeding really do accumulate over generations.  The evidence bears that out.

Of course we should all have suspected this from the get go.  We used to marry cousins and there were lots of children; now we don’t and there aren’t.  That does not alone prove the case, but it certainly places the burden of proof on anyone who asserts that outbreeding is uniformly desirable.  And just what should the standard of proof be?  Inbreed (or rather optimally outbreed) and you must cope with nepotism, hostility to outsiders and perhaps other social ills we have long endured.  Outbreed in the absence of incontrovertible proof that there is no danger and you risk having an aging (a euphemism for “dying”) population. 

It seems to me that the deception works at three levels.  There is the self deception of “choice.”  I hope there is such a thing as choice.  If people have no choice over whom to mate then we have no hope; the current pattern will persist.  But the choice of how many children to have is made not in bed but at the altar.  Take a look at the Icelandic data I cite on my site.  There is a range where, given knowledge of genealogy, you can predict reproductive outcome with ninety percent accuracy. 

The second level is deceit of men with women.  In the movie “The Sting” the Robert Redford character knocks on the door of a woman not knowing she has been hired to kill him.  When she answers and he asks to come in she says, “But it’s two in the morning and I don’t know you.”  He answers suavely, “You know me.  I’m just like you.  It’s two in the morning and I don’t know anybody.”  The emphasis is mine.  That is what men persuade women of.  Bateson’s work on Japanese quail shows that there is an instinct to be attracted to members of the opposite sex that are similar; the more similar the better, provided the pair did now grow up together.  So for the current pattern of outbreeding to occur men must persuade women that the two are alike, must overcome their instinctive preference of men they are really like.  As you point out the physiologic cost to a male of a poor match is trifling while the cost to the woman is life altering. 

And of course the third level is the widespread social level, the narrative that suggests outbreeding is always good which just about everybody I know has bought into.  Some may draw a line at this social border or that, but suggest marrying kin and the reaction is visceral rejection. 

So judge between us, between the evidence and the consensus.  Let me know what you think. 


Linton Herbert MD

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