Blog 2021 10 22 Are you waiting to understand the science of DNA before using it?

I have given several presentations this year about using DNA as just another genealogical tool.  I start by asking how many of them drive AND can explain the science behind the internal combustion engine of their car.  Very few know the science but they drive anyway.  Why?  Because they do not need to know the science to use the car as a tool to get from one point to another.

It is the same with DNA.  If you begin using it as a basic tool in the genealogy tool kit, you will become more comfortable with it.  The more comfortable, the more you start learning new methods to apply it.  It really is that simple.  Just like the auto have various types such as sedan, coupe, convertible, cross-over, and SUV; DNA has three types.  An explanation of each type will help you decide which one to use, or can use, and where to test.

Autosomal DNA (atDNA):  All DNA testing sites utilize the atDNA as the basis of their marketing.  The atDNA test can be taken by anyone and except for close family members: parents, children, and full siblings, the remaining DNA matches are placed into potential categories based on shared centiMorgans (cMs).  I will not fully explain cMs here, except to say that the more shared cMs, the closer the relationship, particularly if there are more and larger shared segments.  Just like gasoline, the more you have, the better off you are.  The atDNA results are good to about the 5th or 6th generation, then the number is so small as to be virtually unusable.

Mitochondrial DNA (mtDNA):  The mtDNA reflects the straight maternal line with virtually no change (mutations) for up to 52 generations.  Anyone can take the mtDNA to identify their mother’s line.  Therefore, if someone takes the mtDNA test the results will completely exclude the father’s family.  This test is currently given only by FamilyTreeDNA® at www.FamilyTreeDNA.com (FTDNA) and is quite expensive.  I personally do not recommend taking the mtDNA if money is tight unless there is a specific brick wall where the test results might be beneficial and the unknown matriarch is within six generations.

Y-DNA Test (Y-DNA):  The Y-DNA reflects the straight paternal line with almost no change (mutation) for up to 25 generations.  Only men can take the Y-DNA test and the results will identify the father’s family to the exclusion of the mother’s family.  This test is currently only given by FTDNA and the cost is less than the mtDNA.  The more markers (points on the chromosome) that are tested, the better.

Understanding centiMorgans (cM):  As stated, I am not explaining what it is, just how to use it.  When your results come back from most testing companies it will not show you have a specific relationship such as Aunt, Uncle, 3rd Cousin once removed.  But several possibilities unless the relationship is a sibling, parent, or child.  It will also report the amount of shared cM and perhaps the largest block or number of segments.  By using the shared cM number and comparing it to the Shared cM Project table listed below, you can begin to see where this person might fit in if you otherwise do not know.

The Shared cM Project:  Many people in the genetic genealogy arena, including Blaine T. Bettinger, and others, put together some great information to help people understand shared cMs, segments, and other DNA results and can be found at https://thegeneticgenealogist.com/wp-content/uploads/2020/03/Shared-cM-Project-Relationship-Chart.png.

What is meant by the cM range, is that you still have to do some traditional research.  Let’s say you share 1,400 cM with someone.  Based on that chart, this person could be Great Aunt/Uncle, Aunt/Uncle, 1st Cousin, Half-Sibling, Grandparent, Grandchild, or Great-Grandparent.  You must determine the reality.  I have two matches, they are siblings but one I share 383cM with and the other 283cM.  Since I know that they are both 1st Cousins once removed, that is where I put them and not as 2nd and 3rd as suggested by the testing company.

Ancestry.com has the largest database, by far, for the atDNA matches.  You can test there and download your raw DNA and then upload, for free, to FTDNA, MyHeritage, and GEDMatch.  GEDMatch is not a testing site but a third-party tool that allows you to compare DNA results regardless of where people were tested.  Do not be overwhelmed if you end up with thousands of matches.  Just work your way from immediate family and Aunts/Uncles and Nephews/Nieces, to 1st cousins, then 2nd, and so on.

Good luck and have fun taking DNA for a test drive.

Start using it and begin feeling more

DNA Clustering and Reports

Evert-Jan Blom, who lives in the Netherlands with his wife and children had a background in Molecular Genetics before getting interested in genealogy. [i] After getting tired of manually trying to connect his matches into groups based on chromosome clustering, he wrote an algorithm (computer code) that did the clustering for him in record time.

This clustering has since become a very popular tool.  In theory, every match on a specific cluster should ultimately share a common ancestor.  While he is no longer allowed to run it against Ancestry.com® matches, his Genetic Affairs will run against your 23 and Me® or your FTDNA DNA matches.  He has also written the same for MyHeritage® and Gedmatch®.

For example, on one of the clusters, I know, based on my own research, that three of the testers descend from the same family as my g-great-grandmother, Lurraine “Lizzy” Elizabeth Reese, the daughter of Samuel Reid and Sarah Catherine Reese, nee Sparks.  Several of the Reese children married Akers and Hamiltons not to mention Akers marrying Hamiltons.  So I can realistically assume that the others who share that cluster must also descend from those family combinations.

These are powerful tools and might be worth your time to investigate.

In addition, he recently added some reports that operate similar to Ancestry’s ThruLines which is based on what others have in their online trees.  However, as the old axiom says, “Garbage in – Garbage out.”  Hopefully, he will improve on this part of code which weighs too heavily on the same or similar name and not on timelines and locations. As I have said concerning ThruLines, if the result does not make sense, do not spend a lot of time chasing it.

As of today, any code that tries to predict pedigree and ancestry is basing the results on trees posted by others and the DNA which these modern testers have attributed to that line.  I was hired awhile back to try and prove that a man who added the nickname Major (he never attained a rank higher than Sergeant) in front of his first name, William, was the son of a county Sheriff who also went by Major since the younger Major one got married in that county.  I proved he was NOT the son because the sheriff’s son was William D., a lawyer who stayed in that county and always signed his name William D.  Whereas the younger Major William moved to Macon, Georgia, and ran a munitions factory.  They were obviously two different Williams.  Plus, the sheriff had two other sons and a daughter.

However, numerous people who have researched the younger Major and his known brother have all attributed their father to the sheriff so ThruLines show the sheriff and makes it appear they share DNA with the sheriff.  They do not.  When clicking on the sheriff, all the DNA matches are via the two misattributed sons and zero sharing with the four known children of the sheriff.

Is this making sense?  To rephrase, the sheriff had four known children, if the younger Major was a son, then his descendants and his known brother’s descendants would share DNA with the four proven children of the sheriff and there are zero matches.  It gives a false narrative.

You can take the information as clues and that is about it.  My oldest proven Thomas ancestor had four children and none are named Joseph.  However, some have attribute Joseph Thomas, born circa 1818, to my known direct ancestor.  However, the reason we do share DNA is that Joseph is actually a grandson of my ancestor and not a son.

That is not to say we cannot use it. I have had several clients move various men in and out of their 4th or 5th great grandfather position just to see the various results.  We are looking for the highest shared cMs with cousins.  Case in point, we are trying to find the father of a Joseph Bishop who was born about 1790, probably in the Spartanburg County area, and appears in the 1810 U. S. Census in Hall County, Georgia.  He then moved to Campbell County, Georgia.  In trying to determine the most logical Bishop family he descends from, we have moved a lot of potential fathers in and out of those positions.  All of the Bishops are related to some extent.  We have narrowed it down to two distinct Bishop families as the most likely.

This does not solve the problem but it does give us a good starting point to spend time researching closer.

Be careful what you believe.  Be careful of any predicted pedigree.

[i] https://www.geneticaffairs.com/about.html

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