September 17, 2015

Per Johan Gabriel Wikström
Minister for Public Health, Healthcare and Sports

Dear Sir:
I am a volunteer diagnostic radiologist for the Pinellas Country Public Health department, and I have noticed that among the many services we offer we address fertility neither to reduce it or improve it although this is obviously an issue of paramount importance to the health and wellbeing of any community.  Neither positive nor negative growth can occur indefinitely without utter disaster.

In fact the formidable text Public Health Practice: What Works similarly makes no mention of fertility.  Otherwise, I highly recommend it.  You might be interested.  All this of course is quite understandable; given the American high degree of diversity, no consensus on birth control has been reached and as for terminating pregnancies we have two camps, which regard each other as shocking. 

 I understand that Sweden has recognized the difficulty of inadequate birth rate, has attempted to improve her own and has failed.  It is time for a new idea, and one must expect that the idea be as shocking as the idea of abortion is to one of our camps and the idea of forbidding it is to another.  Otherwise the idea would already have been mooted and if useful it would have been employed.

The shocking news is that fertility over multiple generations depends on consanguinity: Marry In or Die Out, which is the title of chapter 19 by Professor Robin Fox in Handbook on Evolution and Society, a sociology textbook.  So the short message is to read that chapter and proceed accordingly.  But let me elaborate.  The rest of this letter is optional.

  1. Natural selection is a fact.


  1. If a new species appears in an environment, in which there are many species each optimized for a niche, the first species that can optimize for the new niche has an advantage.  So selection is a race.
  1. For selection to be optimal, speciation must firs occur, else the species is caught in a balance between two opportunities and optimizes for neither.


  1. So speciation is a race. I know of no consensus on how many generations speciation requires; obviously there an is an advantage to a low number.  We will say 2,000.  You may make demur, but suppose it were 40,000.  If our pre human ancestors had the generation of chimpanzees – 25 years – then speciation would take 1,000,000 years.  Not many of our ancestral species lived so long, so that is not plausible; besides there is a race on.
  1. So take a population of animals in a valley mating at random, and divide the valley with a glacier for 2,000 generations.  When the glacier melts animals from the two side cannot – by and large – have fertile offspring.  Speciation has occurred, as we proposed earlier.  When chromosomes from one side meet chromosomes from the other side they cannot function together.


  1. Now instead, let the population increase to 1,000 randomly mating.  That means 2,000 copies of each chromosome.  (We shall ignore sex chromosomes.)  Now taking one chromosome and letting it divide into two, how long will it take on average before it finds itself matched with its nearest cousin.  It will take 2,000 generations.  The chromosomes cannot function together.  The whole population dies. 
  1. Obviously extinction of the fittest is something nature in the long run will not tolerate.  For one thing 2,000 generations is a long time.  Members of the local population will spread their diversity throughout the range of the species.  The whole species will die out.
  1. What has happened is that selection has hit upon a way to do a rough census and kill off the local population if that census indicates too great a size.  This saves the species at large.
  1. The way this is done is that the kinship of a couple is assessed, and if low kinship suggests large population local fertility is reduced in that and in subsequent generations.  This has been demonstrated in children and grandchildren in footnote 1 and demonstrated in terms of marital radius rather than actual genealogy in footnote 2.  At has been shown all the way into great grandchildren (assuming that rich people don’t stay in their ancestral villages) in footnote 3. 


  1. Ten generations is not long in terms of DNA mutations, so the assumed mechanism must be epigenetic.  My own work, footnote 4, indicates that while pre-zygotic infertility that produces increased fertility with increased kinship shows no inbreeding depression, post-zygotic infertility with the same effect over most of its range does show inbreeding depression.
  1.  It has been demonstrated that in plants inbreeding depression is caused by an epigenetic process as show in footnote 5.  Presumably then it is simply a side effect of the post-zygotic mechanism.  That makes sense, since inbreeding depression is obviously not based directly on genes, as their work shows, and it is hard to say why there should be selection that favors it.  

That is about as far as I have been able to carry it.  So far this is research and not advice.  If you are wondering how to get more evidence, a little study could be done.  Offer a couple thousand couples that if they just happen to be third cousins they will get some reward for checking in regularly.  The reward should be generous and extend for many years since in all likelihood they are going to have a lot of babies.  Within a year or two you should know whether the strategy works and be able to offer rational advice.

If you have made it this far, you have nerves of steel.  This next will test them.  You see, post-zygotic infertility is quite evident in males; year after year we have lower sperm counts and less male sexual development.  So it is possible that if old men, old relatives, marry young women the babies can be recovered even if all else fails.  It worked for Lot in the Bible, which is questionable as a scientific document, but it is perfectly logical and consistent with evidence.   

There is an argument from evidence that fertility under conditions of abnormally low average kinship falls precipitously, stabilizes for a bit and then collapses altogether.  That has shock value and might be useful to you.  You can see it coming.  According to, if you graph Swedish birth rate per woman against age at first marriage for women you can see the birth rate fall and stabilize.  And at that moment, age at first marriage starts an inexorable climb of 1 year every three years.  When they are all marrying at 40, you’ll get your headlines.  Run all the countries at once and see that this is the general pattern, but Sweden dies about first. 

I hope you will give this the attention it deserves.  Of course I am at your disposal if there is any way I can help.


M. Linton Herbert MD

1) An Association between Kinship and Fertility of Human Couples Agnar Helgason et al. Science vol. 329 no. 5864 February 8, 2008 page 813 – 816

2) Human Fertility Increases with marital radius. Rodrigo Labouriau and António Amorim.  Genetics vol. 178 January 2008 page 603

Comment on “An Association Between the Kinship and Fertility of Human Couples,” Rodrigo Labouriau and António Amorim Science vol. 322, page 1634b December 12, 2008

3) Low fertility increases descendant socioeconomic position but reduces long-term fitness in a modern post-industrial society Proc. R. Soc. B 2012 279, 4342-4351 first published online 29 August 2012 Anna Goodman, Ilona Koupil and David W. Lawson

4) Fluctuation of fertility with number in a real insect population and a virtual population M.L. Herbert & M.G. Lewis African Entomology 21(1): 119–125 (2013)

5) Vergeer, P.; Wagemaker, N.; Ouborg, N. J., Evidence for an Epigenetic Role in Inbreeding Depression, Biol. Lett. doi:10.1098/rsbl.2012.0494 Published online.

p.s.  I tried sending this by email, but it appears you folks have blocked that line of communication.  Accordingly I shall attempt to send this by regular mail since it is so very important. LH

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