June 14, 2015

Dr. Khaled Amiri
Head of the Department of Biology
College of Science
United Arab Emirates University
P.O. Box 15551
United Arab Emirates

Dear Dr. Amiri:
We met several years ago at an international genetics convention in Melbourne, Australia.  I was there to present a poster on the issue of diversity and fertility: you can’t have much of both for very long.  As we were chatting, I asked you how long the generation time of camels might be.  You very kindly answered that traditionally camels are milked after calving, which suppresses ovulation so that generation time is long; your best guess was about seven years.

The reason I wanted to know is the following logic.  Let us say it takes two thousand generations of isolation to accomplish speciation.  This is plausible from a study done of mice in the Canary Islands, where mice were only introduced after the time of Columbus and by now have developed into a different species by karyotype in each valley.  Since speciation precedes selection, by and large, and since selection is a contest of speed, the form that undergoes speciation faster has a head start in selection.  Thus it would be expected that to a first approximation all animals undergo speciation at the same rate.

So consider a valley with, lets say, rabbits.  A glacier divides the valley for 2,000 rabbit generations, then melts and the rabbits from different sides can get together.  But they cannot have fertile offspring.  No instead of the glacier let us say that there are a thousand rabbits in the valley, mating at random.  Two siblings get copies of the same chromosome from one parent.  These are as similar as chromosomes can be.  It will take them on average about two thousand generations to get back together in the same rabbit.  When they do, they are as different as they would be had they been separated by a glacier.  Since this is true of every part of every chromosome, no pair can have fertile offspring, so the whole valley dies out.

Two thousand generations is not long for nature, but it is long for an individual.  So that valley is a threat to every rabbit population with which it overlaps.  The whole species is under threat.

Well nature is not going to tolerate a scenario in which every animal winds up dead, so nature has instituted restrictions of population size: too much for too long and the plug gets pulled.

This whole idea is laid out in a video on Youtube:
You might recognize Jennifer in the cast.  She is married now and has a two month old baby.

Years ago we were told that camels had been domesticated in Bactria and some were then taken to Africa, and since that time have undergone speciation so that although a Bactrian-dromedary cross can have offspring, after a few generations hybrid breakdown occurs; the two are now different species.  Since there is no Egyptian hieroglyph for “camel” but there is a Hebrew letter (the third in the alphabet) for “camel,” it should be possible to say roughly how many years the two lines have been separated and thus how many generations to speciation.  The plausible dates suggest that in that case speciation occurred in less than 2,000 camel generations.  That’s reasonable; hybrid breakdown should be an early change and karyotype should be a late one.

Alas, current thinking is now that the first domesticated camel was the dromedary in the Sudan, the camel having made its way there without the help of people at some time nobody is willing to guess at.  So the whole argument collapses, but it only collapses for camels.  It still works for mice.

I have spent the years since we met in pursuit of this issue.  After all, nothing is more important than babies, and if something is going to take our babies away, we would do well to understand it.  I got a paper published, which confirms that as kinship declines, so does fertility and this accumulates over generations in fruit flies.  I shall attach the paper. 

Currently I am trying to work out the molecular genetics of the process: it has to be epigenetic.  It’s too fast for DNA mutations. 

To say I have met with obstruction at every turn would be an understatement.  Not to complain, but people don’t even argue.  They just ignore me.  Maybe they are thinking, “Why you want to say that women ought to marry only among a certain group, not just marry whom they please.”  I am happy for women to marry whom they please, but I think everyone should know what the likely result of the choice would be and I cannot say I am warmly disposed toward those who by inaction would conceal the truth. 

So I thought that someone who was from a more traditional culture, where such things could at least be discussed, who was a geneticist – preferably a molecular geneticist – and who was friendly and courteous might take an interest.  So I am being bold enough to write and ask you what you think.  Here is a link with the bulk of the evidence I have accumulated since we met:

Otherwise things are well here.  I trust all is well with you and your work with fragile X syndrome continues to go well.


Linton Herbert

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