Previously, the charts I have drawn to illustrate our developing understanding of phylogeny for the I-Y33765 clade have been based on Single Nucleotide Polymorphism (SNPs) results from FTDNA Big Y-700 next generation testing. In this draft however I have sketched a tree which shows the estimated positions of Short Tandem Repeat (STR) marker mutations downstream from Y33765. My interpretation is based on comparison of the results of eight men who have each tested 111 STR markers at FTDNA.
Those mutations shown in blue type on the chart are "back" mutations in which the number of repeat motifs at that marker has been reduced compared to the upstream value shown in black, while "forward" mutations, in which the number of repeat motifs has increased, are shown with red characters. The chart demonstrates how STR markers mutate randomly over time with both "forward" and "back" mutations happening at an apparently similar frequency on each of the lineages within our clade.
Most of the observed mutations are, as might be expected, in the fastest mutating STR markers but four of these changes have occurred in markers with the slowest rate of mutation. All these slow marker mutations have occurred at some point during the last ten to fifteen generations, so within the conventional genealogical time-frame. One of the English lineages, Clement IN82043, at marker DYS717 shows an increase from 19 to 20 repeats. On the Swedish arm of the clade, Eklund IN78306 has a "forward" mutation from 18 to 19 repeats at DYS587 and a "back" mutation from 14 to 13 repeats at DYS497. Lastly the Swedish, Jacobsson IN70815 lineage has a "back" mutation from 12 to 11 repeats at marker DY568. Again, we can interpret these changes as demonstrating the completely random nature of alterations in Y-chromosome STRs.
The most significant relational change in this latest version of the I-Y33765 tree concerns the expansion of the English branch downstream from I-Y33767. Comparison of the 111STR results for Clements B742594 (in previous iterations of the I-Y33765 tree shown as YS32054) with those for the other English men has shown that he is most closely related to Clement 236748 and Clement 282009. This finding prompted a reconsideration of the known documented genealogies for these three men and, as a result of this, a putative connection has been found between them with their most recent common ancestor (MRCA), George Clement, who was baptized at St Mary the Virgin, Compton Dando, Somerset, 1st December, 1678. This finding would seem to indicate that the genealogies of all the presently known instances of I-Y33765 in England can now be shown to originate from an area of north-east Somerset close to the parish of Clutton. Previously the earliest known Clement ancestry for 236748 and 282009 was in south Gloucestershire.
Regular readers will recall that I have several times discussed my feeling that a plausible explanation for the localization of an originally Scandinavian I-Y33765 male lineage in north Somerset can be proposed by linking its patriarch to north Somerset manors that, like Clutton, were owned by men of Scandinavian descent during the two generations that preceded the Norman Conquest. It seems to me this latest redefinition of genetic relationships on the English arm of I-Y33765 supports this hypothesis. If you are interested in more discussion on this theme then I suggest you may want to look at these earlier blogs published 24 September 2020, 21 & 23 October 2020 and 11 April, 2021.
Click on image to enlarge
In the above post, my conclusions about the genetic relationships between the five English Clement men, that I had based on a comparison of their Short Tandem Repeat (STR) 111 marker test results are incorrect. Consequently, in the above chart the arrangement of branches downstream of Y33767 is wrong and should be ignored. My mistake has been confirmed by the "next generation sequencing" results from the BigY-700 analysis completed for Clements B742594 in July 2021 (for a full update please see my blog published 8 August 2021).
It seems to me that it is probably helpful to leave this incorrect post on-line because it illustrates the folly of relying solely on STR markers and nicely demonstrates that only Single Nucleotide Polymorphism (SNP) mutations can be considered a "gold standard" marker for genetic genealogy.
JAC, 8th August, 2021
