Ed Ralston
May 19, 2019
R-M269 (Subclade R-BY15421) members of the Ralston Project appear to be related, descending from a common ancestor (MRCA). This analysis shows the following:
- All the R-M269 (Subclade R-BY15421) members are indicated by Family Tree DNA as being related at the 37-marker and 67-marker test. All except one have also tested at 111 markers and are related or probably related at these levels also. A Matrix showing the genetic distances at 37, 67, and 111 markers are shown below.
- With any group of related y-DNA matches, the modal or most common value for each STR is the presumed STR value for the most recent common ancestor (MRCA). This presumes that the matches all generally inherited the y-DNA of the MRCA, except where mutations occurred. A chart showing these mutations, or differences from the mode, for each member at 37, 67 and 111 markers are shown below.
- A matrix below shows the genetic distance between each member and the number of mutations of each member to the MRCA.
- There are suspected (closer) cousins among these members. This is discussed below.
- Some STRs mutate faster than other STRs. If a mutation occurs on one of these markers it may not be an indication of the passage of many generations. Some researchers disregard the fastest mutating STRs when doing analysis. Charts showing the member’s differences from the mode disregarding the fast mutating STRs at 37, 67, and 111 markers are shown.
- This analysis implies that these members are all related. A hypothetical descendancy tree from the MRCA is shown at the end of this report.
A limitation of this and any y-DNA analysis is that a mutation might occur on an STR several generations back, then at some point that same STR might mutate again and revert back to the original, which would look like no mutation at all. This is not likely, except on markers that mutate quickly. Another complication is that all or the majority of the members of a group of matches might coincidentally all have mutations on the same marker at the same value, which would skew the modal value. The larger the group, however, the more remote is this possibility; nor is this likely on slow mutating markers.
The following charts are the genetic distance matrices at 37, 67 and 111 markers for the R-M269 (Subclade R-BY15421) members of the Ralston Project. These matrices shows that these members are all related or probably related to each other.
Comparing the matrices at different testing levels shows the importance of testing at the highest level possible. At the 37-marker level this group appeared to be all related or probably related. However, at 111 markers, the group ranges from probably related to only possibly related. At this genetic different a common ancestor could be as close as 10 to 14 generations, or as far as 18 to 27 generations. This might be adjusted for fast mutating markers, which will be discussed later.
Modal Values
Since all these members are possibly related, another factor can then be considered in analyzing their y-DNA. Dr. Allan H. Westreich wrote in his paper, Using a Y-DNA Surname Project to Dig Deeper Into Your Genealogy: A Case Study, “A common method (Gleeson, 2015b) for determining the genetic proximity of a group of haplotypes is to compare each of them to an approximation of their MRCA’s haplotype. This haplotype is often best estimated by the modal haplotype (Gleeson, 2015b) of the group, which is calculated as the haplotype consisting of the modal (most frequent) values on a marker-by-marker basis.”
On the Ralston Project home page, if one selects to view DNA test results, then selects “Colorized Chart”, the resulting chart shows the modal value, “MODE”, for each subgroup in the project. The chart also highlights STR values that differ from this mode. By counting the number of highlighted numbers, one can find their number of mutations since the group’s MRCA.
Modal Difference Chart: Following is a chart that shows all the STRs where each member of this project group differs from the modal value, or the STR of the MRCA. For simplification, the STR values where all agree are omitted. The modal values in this analysis were based on an actual mode calculation for each STR using an Excel spreadsheet with the exception of marker 34.
Note the 34th marker CDYa. There values are 38, 37, 36, 38, and 37. Mathematically the mode value could be either 37 or 38. However, when considering that mutations normally occur in single steps, it is more likely the MRCA value at that marker was the median value of 37, with two mutating up one and one mutating down one.
Note also that on marker 59, P.R. and R.R. have the same mutation value. This might be coincidental, but that is less likely of a slow mutating marker, as is DYS520. This could be an indication that P.R. and R.R. descend from a more recent common ancestor than the MRCA of the group, and both inheriting this mutation from that ancestor.
Totals are shown at each testing level for the number of mismatches to the mode or mutations since the MRCA. The totals range from 3 to 6 at 111 markers.
Following is the genetic distance matrices again – this time with the mutations from the MRCA added as determined from the Modal Difference Chart above:
OBSERVATIONS:
1. COUSINS
P.R. and R.R. share a mutation value that the others in the group do not have. This could indicate an intermediate common ancestor, meaning these two are closer cousins than the rest. There are speculated lineages that show this connection.
MUTATION RATES
Additionally, different STR markers mutate at differing rates. Thus, a mutation on one STR might carry more significance than a mutation on another, since a mutation on a marker that rarely mutates would be an indication of many more generations for the mutation to have occurred. Again, note on the Ralston Project home page, if one selects to view DNA test results, then selects “Colorized Chart”, the STR markers listed across the top are colored. Those with a red background are the fast mutating markers.
Several web sites, such as http://adamsfamilydna.com and http://www.taylorfamilygenes.info, have posted tables showing the average mutation rate of each STR. Of the 111 markers tested at FTDNA, the top four fastest mutating markers are CDYa, CDYb, DYS712, and DYS449. Because these markers mutate so quickly, some analysts exclude these markers from their analysis.
If these fast mutating markers are excluded the results are as follows in these revised Modal Difference Chart:
Following are the revised genetic distance matrices, excluding fast-mutating markers:
CONCLUSION:
The accuracy of these analyses is improved by having as many matches as possible in the group. Having more matching members makes the modal calculation more accurate and offers greater possibilities for determining if intermediate ancestors existed.
Additionally, accuracy is improved by having as many as possible testing at 111 markers. Note in the chart that four members show a mutation count of 2 to 4 from each other 37 markers, indicating the group is related. However, at 111 markers the genetic distance is 6 to 9, meaning the group is only probably related.
The exclusion of fast-mutating markers results in the appearance that the group (at 111 markers) the greatest genetic distance is 7 – probably related. However, if A.R.’s genetic distance ranges from 3 to 5 (Related) with each of the other members, then, each of the other members must also be related.
The most likely scenario for the path to the MRCA is that there are branches with intermediate ancestors, from which closer cousins descend.
