August 9, 2014

Peter de Knijff
Department of Human Genetics
Leiden University Medical Center
Post Office Box 9600
2300 Leiden

Dear Dr. de Knijff:
I have read your piece with great interest.  (Peter de Knijff How carrion and hooded crows defeat Linnnaeus’s curse SCIENCE vol. 344 no. 6290 June 20, 2014 page 1345)  I am somewhat reminded of a comment a lecturing pathologist made to his colleagues, “We are not the last test because we are infallible; we are infallible because we are the last test.”  The day must come when complete analysis of genome and all epigenetic markers is commonplace, and that will ultimately trump any decisions about speciation that we can actually understand. 

What most peaked me was your pointing out that speciation may depend not solely on DNA differences but on epigenetic markers that restrict fertility.  I have taken an interest in what you might call “normal variation in intra-specific fertility,” not to put to a highfalutin tone on it.  (M.L. Herbert & M.G. Lewis Fluctuation of fertility with number in a real insect population and a virtual population African Entomology 21(1): 119–125 (2013))  In the lab and in the wild fertility is responsive to mating pool size – the equivalent of average kinship – irrespective of environmental influences (or choice if you are looking at people).  This effect works itself out over five or ten generations, far too fast for DNA base speciation, and my best guess is that it is due to an epigenetic mechanism.  Reading your remark that there seems to be an epigenetic effect on fertility I find encouraging.  Can you tell me where I might learn more about this?

Thank you.


M. Linton Herbert MD

I am delighted to report that I received a prompt and courteous reply from the professor.  When I asked for clarification on a few points, that was forthcoming as well.  If I ever complain of being ignored, please remind me of this excellent man. 

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