March 19, 2012
to be posted on and

Olen Kalkus
Princeton Academy
1128 Great Road
Princeton, NJ 08540

Dear Olen Kalkus:
I read with interest your response (Single-Sex Education Results One Sided SCIENCE vol. 335 no. 6065 January 13, 2012 page 165) to the article (D. F. Halpern et al. The Peudoscience of Single-Sex Schooling SCIENCE September 23, 2011 page 1706) claiming that results of coeducational education are as good as or better than results from education in schools that teach to a single sex.

A glance at the firestorm the article raised makes me suspect that there is room for differences of opinion here, so I shall not make bold to hazard an opinion of my own.  Instead I should like to introduce, perhaps impertinently, a different issue. 

Students do more than study at school; they fall in love.

And that proves to be important.  I suppose it is well recognized, and widely applauded, that girls who graduate from high school have fewer children than those who do not.  This is generally thought to be a Good Thing and that education is thus seen to be Empowering them to Take Charge of Their Lives and anyway there are Too Many Babies in the World.

However there is a slight flaw.  I grew up in a school system where it was illegal to teach evolution, yet found I was better prepared for college than graduates of elite college prep schools and indeed had a better understanding of evolution from an earlier age.  My excellent teachers did not let a bad law get in the way of good education.  So, in spite of having lately developed reservations about Charles Darwin (and my reservations hold no comfort for those who would prefer something more magical) I do have a reflex of looking for the selective advantage.  And education, alas, appears to offer a selective disadvantage.  That is not something to applaud.

Maybe there are too many babies in the world, but I think there are not too many babies among the highly educated and productive. 

After some work I have concluded that fertility depends on kinship.  If there is not enough kinship – it turns out you don’t want to go out past sixth or seventh cousin – there will not be enough fertility for long term survival of the community, barring immigration from somewhere with a mating strategy that does result in adequate consanguinity. 

You may think this sounds mad, but the evidence is very compelling for those who actually look at it.  Here is a link, complete with graphs and references and an explanation of why evolution had to do this to us.

So girls and young women who go to coeducational educational institutions are likely to fall in love with classmates, and those classmates are likely to be unrelated.  (All right, I know, everybody is related, but I mean out past ten generations of separation.)  That, rather than any improvement in the wisdom of the graduates, accounts for all, yes all, of the shortfall in the fertility of the educated.  Check that web site if you doubt it.

I admit to one difficulty here.  In their rejoinder to the challengers, Halpern and colleagues state that graduates of coeducational institutions are less likely to get divorced than those who have had single-sex educations.  I should not have expected that.  On the other hand, it only surprises me; it does not contradict the general thesis. 

I thought you might be interested.  Tell me how you feel about it.


M. Linton Herbert MD 

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