Most Dreaded Terror 4 Iceland

https://www.youtube.com/watch?v=hVATVF-816U
It is 25th of February 2018, and again you cannot possibly imagine how excited I am until some day you get to the end and understand it.  And again, I am worried that I might make this so light as to be silly or so dark you can never make it through. 

  1. We are in pursuit of whatever makes inbreeding kill babies, because it does not stop there.  We have seen that the mechanism is inherited but not genetic and it stabilizes a population at some moderate size, neither too small to survive nor too large.  We have seen the Sibly curve, which is supported by massive amounts of data, which shows the mechanism in effect, stabilizing populations of mammals, birds, fish and insects.  It would be understandable for a prudent person so say, “Ah, but those are all dumb animals.  We humans choose whether to reproduce.”  And to a degree we can, but we need to look at some human data.
  2. A team led by a man named Helgason looked at data from the enormous Icelandic genealogy.  Then he compared the kinship of couples with how many children they had.  This is what he got:


“An Association between Kinship and Fertility of Human couples,” Helgeson et al. Science vol. 319 February 8, 2004 page 813.
Gaze at it a bit and then let me tell you what they have done.  They chose a large number of couples.  They recorded the number of children each pair had.  They calculated the kinship of the couples by going back ten generations and counting how many ancestors they shared in that generation.  Then they calculated kinship in terms of say first cousin if they shared a quarter of the possible number of ancestors, second cousin if they shared an eighth and so forth.  Obviously this is not the way we ordinarily recon kinship.  I’m sure very few can name all their ancestors for 10 generations back.  Then they lumped the data so that every couple between say third cousin and fourth cousin was labeled “fourth cousin or closer.”  I might have suggested “third cousin once removed.” 
Then they took the average number of children in each fraction and “normalized” it, which means they compared it with the average across the country for that year.  Thus zero means the same degree of fertility as the Icelandic average. 

  1. We can immediately recognize the Sibly curve.  Do not think for a second that humans are exempt.  The effect is not enormous, going from roughly 10% below to 20% above the national mean, but the effect is clearly not trivial.  
  2. Now look at the error bars.  They are very tight.  Those are ninety percent confidence limits.  There cannot be much else determining fertility.  Any factor other than kinship of the couple has to squeeze into that little interval.  That includes choice.   It will be more extreme when we look at the next generation.
  3. Before that, however, look at “eighth cousins or closer.”  That is the most distant relationship they examine.  Either they have thrown away data or ninth cousins are vanishingly rare or totally absent.  That alone should give a prudent person a maximal warning. 
  4. Helgason’s team went further and looked at the next generation, the grandchildren:

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

 

Sorry, Dreamweaver and Word are at daggers drawn. Check the videoor Fritz's talk on population collapse, posted here June 5, 2017 under "Summaries" on nobabies.net home page

 

 

The axies are the same.  Vertical axis ranges from about equal to the Iceland average to 15% above.  Thus in only two generations the kinship choices can change fertility by about 40%.  The horizontal axis is “second cousin or closer,” then “third cousin or closer” and so forth, but giving the degree of kinship numerically rather than using an altered form of usual usage. 

  1. Notice that while “second cousins or closer” gave a maximum number of children, that does not give a maximum number of grandchildren.  To my eye third cousins should have the most grandchildren.  Don’t start muttering “inbreeding depression” just yet.  First cousin once removed still produces more grandchildren than does anything more distant than about 6th cousin which is close to “zero” or the Iceland average, and which I would guess to be reasonably close to replacement. 
  2. Since there is no reason to expect a couple to have exactly the same kinship as their respective parents, much of the variation in the number of children a couple might have (remember the 90% confidence limits) must be due to the kinship of the parents.  On the face of it fertility in that country is due to kinship issues AND NOTHING ELSE.  Maybe you can choose your mate, but that choice having been made the number of children cannot be changed. 
  3. We shall see in a later video that people and mice mate for status and not attraction. 
  4. We shall also see, later, that folic acid supplement can affect fertility, but for now the evidence at hand only supports the concept that kinship issues absolutely determine fertility. 

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