Analysis and Interpretation of Current Pettypool DNA Results

The chart shown below lists the current Pettypool DNA Project members whose results have been posted.  The chart is separated into two parts based on what is known about the origin of the study participants.  Those with a verified paper trail showing descent from Seth of the third generation are grouped together as are those with either a paper trail or probable descent from William of the third generation. This separation has been done in an attempt to discern any patterns of mutations that might characterize these two main branches of the family. 

The chart has been colored to make use of analytic techniques suggested by Diana Gale Matthiesen at her web site 

< http://dgmweb.net/GenealogyHome.html>.  The values of Pettypool participants for the genetic markers (Y-STRs) heading the columns of the chart permit an assessment of relatedness based on what Matthiesen calls signature markers.  Matthiesen distinguishes the following four classes of markers (descriptions copied from her web site):

1.  Modal Values.  These values are the most common ones for the entire haplogroup subclade; and, because theyare the most common values to have, having them is literally unremarkable.  Sharing the haplogroup modal values with a family is of virtually no significance beyond the fact that you're related somewhere back in time — as we all are if you go back far enough.

2.  Signature Markers.  These are non-modal marker values shared by everyone in a family.  They consistently and, in combination, uniquely distinguish a family.  Presumably,these are the mutations possessed by the family's progenitor within "genealogical time." 

3.  Private Markers.  These markers are unique to one test subject.  The mutation has happened in the individual's descent from the family progenitor, but we don't know in which generation.  As more cousins are tested, private markers will turn into branch markers, unless the mutation occurred in the test individual himself.  Because the latter can be the case, it is not irrelevant to test a brother, father, or first cousin.  Anyone with a private marker should test cousins (viz., a 1st cousin, 2nd cousin, 3rd cousin,etc.) until the location of the mutation is determined.

4.  Branch Markers.  These are marker values shared by two or more members of a family, but not the entire family, in other words, by a branch of the family.  Once some one has proven their membership in the family by possessing its signature markers, the branch markers become highly important because these markers most likely represent a shared common ancestor more recent than the family's progenitor.  (In some cases, a shared value on a volatile, fast mutating marker may mean the mutation happened more than once in the family; paper genealogy and the testing of cousins can determine which is the case.)

Making use of the “signature marker” technique, thefollowing observations can be made about the Pettypool DNA project members. 

·      The haplogroup R1b is modal for the Pettypool family, and these values are shaded violet in the chart.   (For more information on the R1b haplogroup see http://en.wikipedia.org/wiki/Haplogroup_R1b_(Y-DNA)   R1b is the most frequently occurring haplogroup in the UK and Western Europe, reaching nearly 80% in some areas.  As would be expected, most of the table appears violet because most of the Pettypool participants match the modal values for the R1b haplogroup at most markers.  As a consequence, these markers are not useful for genealogical purposes and can be considered irrelevant for testing genealogical relatedness.

·     The markers unique to the Pettypool family are shaded in light green.  These markers differ from the modal R1b markers and do so consistently among all Pettypool participants (with one exception to be discussed under branch markers below). These markers (DYS389-1=12, DYS389-2=28, DYS464a=14, DYS464c=16,DYS456=15, CDYa=37, and CDYb=37) are the Pettypool family signature markers and represent a good approximation of the haplotype carried by the Pettypool immigrant ancestor and progenitor, William (b. 1630 London, d. ca 1665 probablyMaryland).  Only one memberis so far a perfect match to the modal Pettypool haplotype:  Kit # 186484 who is likely descended from Phillip (4), son of William (3). Although not necessarily of any genealogical significance, what this means is that this participant’s branch has experienced the fewest mutations in descent from the progenitor (at least among those markers represented in the tested segments). 

·      The values that are scattered around the table and highlighted in red are the private mutations that have occurred in individuals in their descent from the progenitor.  In some instances(e.g. DYS 464d), the same mutation may have arisen independently in several men as DYS464 is a multi-copy marker that has been categorized as fast mutating.  Note that five of the seven men whose suggested ancestry is from Seth (3) have values of 18 at DYS464d although the Pettypool modal value is 17. Accordingly, I was tempted to call this marker a branch marker until I realized that Kits # 11396 and 108232 (who differ on this marker) are more closely related (3^rd cousins) than either is to any of the othermembers of the “Seth group.”  There are two possible explanations:  1) the value of 18 for this marker may indeed characterize the Seth branch but in a few individuals there has been a mutation back to the modal value of 17, i.e. Kits # 111396 and 86831, or 2) the value of 17 may be present for most descendants in the Seth branch and the current sample is, by chance, unfairly weighted with those carrying the mutation leading to a value of 18.  Because DYS464 is a volatile marker, it is not possible to choose between these two competing explanations.   Until a bigger sample of men from both family groups is tested, I have chosen, for the time being, to interpret the inconsistent DYS464d values as evidence of a series of parallel private mutations in the Seth branch. 

·      With the exception of DYS464d, about which I have already spoken, all the other mismatches with the modal haplotype appear, at the moment, to represent isolated mutations.  Whether they are unique to the particular individuals tested or represent a potential branch marker cannot be determined until cousins of those carrying the mutated marker(s) also are tested. 

·     Two sets of potential branch markers are highlighted in bright yellow.  The marker shared by Kits # 86831 and 33153 is an almost certain branch marker as these two participants have a value of 18 at DYS576 while everyone else is 17 at that marker.  Though these individuals are uncertain of their exact Pettypool lineage they are both certain descendants of a Talley family that paper evidence suggests was in close association with members of the Seth (3) branch of the Pettypool family in the late 18^th and early 19^th century.  Their pedigrees show that their most distant common ancestor may have been the individual whom evidence suggests was fathered by a Pettypool man. Testing of descendants of yet other sons of this common Talley ancestor will help confirm the existence of the branch marker and when it might havebeen acquired.  Among subsequent Pettypool men who are tested, a value of 18 on this marker along with traditional genealogical evidence also might lead to discovery of the generation associated with the adoption or other non-paternal event that generated this branch of the Pettypool family.

·     The second possible branch marker is shared by Kits # 182173 and 87253.  Both men are value 36 at DYSCDYa while all others are 37 at this marker, which is also (as described above) a Pettypool signature value.  At the moment there is insufficient paper evidence to link the two in recent time, but the best available evidence suggests strongly that they both descend from a son of William (3).  Although neither has unquestioned evidence for ancestry in the third generation of the Pettypool family, the most distant verified ancestor of each is known to have left South Carolina in the early 19^thcentury.  So far, however, no connection between them has yet been made.