From: rail@greywall.demon.co.uk   
      
   On 22/01/2020 10:34, Evertjan. wrote:   
   > Ian Goddard  wrote on 21 Jan 2020 in   
   > soc.genealogy.britain:   
   >   
   >> I have a family tree whereby a group of siblings have four lines of   
   >> descent from the same couple.  For three of these there are 7   
   >> generations and for the other there are 6 generations.  The 7 generation   
   >> descent would give 128 distinct genealogical roles at this level and the   
   >> 6 generation descent would give 64.  In fact I find 10 individuals   
   >> filling 24 of these roles so there are 14 "missing" ancestors due to   
   >> pedigree collapse.   
   >   
   > They are not really missing,   
   > as it is the norm in an ecological niche called earth.   
   >   
   > When the niche gets smaller, called isolation,   
   > the phenomenon gets more pronounced,   
   > like among sects, monoglots or on remote islands.   
   >   
      
   Doesn't need to be remote islands, I have pronounced examples in my   
   wife's family in both North and South America. Both as a result of the   
   families being there in early colonial days.   
      
      
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   Graeme Wall   
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