November 10, 2013

Marcus Kronforst
Department of Ecology and Evolution
University of Chicago
Office Z202
773 702 5125
Subjects: Adaptation, speciation, evolutionary genomics, population genetics

Dear Dr. Kronforst:
I recently read an article about your work in ECONOMIST.  Alas I have lost the issue (I know not how.  I never throw anything away.) but it was about speciation and mimicry in some South American butterflies.  South American butterflies have long had a place in my heart.  When I was a child there was a museum in the Seagal Building in Gainesville.  It had more wonderful things in a limited space than any other museum I ever visited.  Ultimately the museum got more space at the University of Florida.  The old collection was taken down forever.  One of the displays was a collection of iridescent blue South American butterflies.  There must have been thousands of them.  They were breathtakingly beautiful, but there was something more in the fact that there were so many when one alone would have made the biological point.

There was a cartoon in old Punch Magazine.  As I remember a detective and a constable were inspecting a room.  A man wearing a strange smoking jacket and strange pants and shoes lay dead on the floor.  His face was rat-like.  In one hand he held a paper that had an enciphered message.  The other hand had dropped a glass of poisonous looking liquid.  A kris was imbedded in his chest.  A venomous looking snake hung from a hook by the ceiling in one corner and a huge spider dangled in another corner.  The bookshelves had been rifled.  A shadowy figure was passing the window.  There were arcane symbols posted on the walls.  And so it went on and on.  The detective was saying, “You know, somehow I think we’re never going to get to the bottom of this.” 

So it was with those butterflies.  In their profusion they seemed to be saying the same thing.

Speciation has been part of something I have been looking at for many years.  The most abstract issue is that since speciation happens, and speciation must occur in order for selection to be effective, then there is a race to speciation just as selection is a race.  In mammals the evidence I have stumbled across (mice in the Canary Islands, rabbits in the Azores, one and two humped camels) suggest that a couple of thousand generations of separation in mammals is enough to have a probability of speciation. 

If that is the case, then a stable randomly mating population of mammals cannot exceed 1,000.  This of course flies directly into the face of Malthus.  Here is a link: to a place where I lay out the logic a little more formally (look for the yellow chromosome drawings) along with the bulk of the evidence I have to support it.  There simply must be a mechanism that prevents populations from growing without limit. 

I tested the proposition with fruit flies and attach my paper.  Fruit flies seem to be able to tolerate much larger populations than mammals, but that tolerance is not infinite.  It can’t be.  Else speciation would fail and as one after another form died out all complex life would perish. 

Let me know what you think.


M. Linton Herbert MD

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