August 9, 2012

to be posted on

Nathaniel Comfort
Associate Professor
History of Medicine
Johns Hopkins University
1900 E. Monument St.
Baltimore, MD 21205
twitter: @nccomfort

Dear Professor Comfort:
I have read the article you sent

© The Author 2006. Published by Oxford University Press. All rights reserved.
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Advance Access publication on June 8, 2006 doi:10.1093/jhmas/jrl001
“Polyhybrid Heterogeneous Bastards”:
Promoting Medical Genetics in America
in the 1930s and 1940s

with great interest.  Thank you again.  You demonstrate an ability to deal with politically difficult, emotionally charged, technically complex issues.  I hope some day to put that skill to work, but before I unload my principle interest I shall read the two books you suggested. 

You are absolutely right that William Allen is the man I have been looking for.  His work on genetics among the people of the Appalachian Piedmont, where families were big and people kept track of them, uncovered much. 

He demonstrated that human genetics could be understood in part by Medelian inheritance.  If cousins shared a heterozygous state for a deleterious recessive, some of their offspring might suffer from the homozygous state.  Well and good.

Somehow this truth got morphed into the eugenics proposition, “You must never engage in inbreeding,” more commonly phrased in my experience as,
“If you marry a cousin your children will have two heads,” which of course is stuff and nonsense.

Now it is true that inbreeding is always bad.  That’s because the definition of inbreeding is reducing genetic diversity until there are destructive effects.  There is simply no word in English for reducing genetic diversity to a point that is short of inbreeding.  Patrick Fox uses the phrase, “optimal outbreeding.”  That is based on observations of things like the fact that if there is too much diversity then the major histocompatibility group complex will not be able to provide the best immune defenses.  At the same time, if there is too little diversity the immune defenses will be compromised.  As it turns out optimal outbreeding means getting as close to inbreeding as possible without quite getting there.

It is indeed a pity that Allan and his fellows were not better at statistics.  As they say, it has been shown countless times that beating drums will restore the sun after an eclipse.  You don’t know that until you do the control and not beat drums.  When they found that patients with “undifferentiated feeblemindedness” had a higher incidence of Rh-negative mothers they should have looked at the fathers; they would have found a higher incidence of Rh-positives.  (I am a bit puzzled by the notion that the Rh antigen can cross the placenta.  The antigen is on the surface of the red cell and thus crosses the placenta no more often than any other site on the surface.  We were told that it was the antibody that could cross the plancenta.)  It is the combination of Rh positive father and Rh negative mother that causes problems. 

Charles Darwin decided that inbreeding was bad and said as much.  According to Incest and Influence by Adam Kuper Darwin’s own son compared the “insane” of Bedlam (insanity I guess being the same as undifferentiated feeblemindedness) with the general population and he found that there was in fact less insanity among people whose parents shared a last name than among the population at large.  Had the Americans done a control, they would probably have found the same thing in the Appalachian Piedmont.  Then perhaps we might have been spared the current intense prejudice against optimal outbreeding.  The effect was small as you would expect if you did a little arithmetic on the assumption that the prevalence of Rh negatives in London and Appalachia is about fifteen to twenty percent. 

Allan seems to have been a man of good intentions, but I have been holding him responsible for the prejudice.  But nothing in your article justifies that, and besides, I guess I can’t blame Darwin’s purblindness on him, can I?

If you have any ideas of why this prejudice arises in defiance of the biological facts I should be most happy to know.  After I have read the books I hope to get back to you on the topic of my major interest, but there is no need to trouble you if the information is already written down.


M. Linton Herbert MD 

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