Genealogy Consanguinity & DNA — #Genealogy #DNA #Kinship

by C. Michael Eliasz-Solomon

Consanguinity Chart Now … by John J. Tierney used via CC rights

 This is a beautiful data visualization tool of “relatedness” (Consanguinity) between yourself and an ancestor/descendant. Stanczyk loves good #STEM.  Mr. Tierney modified his excellent chart to add, “What percentage of DNA do you share with your family members”.

Kinship is characterized by the sharing of a common ancestor(s).  Consanguinity is derived from its Latin root:   consanguineous ∴  “of common blood”.

Today, I wanted to use this excellent chart to talk about the three types of Genealogical DNA tests:



autosomal DNA


This way a genealogist can determine for him/her-self what benefit each type of DNA testing offers. mtDNA is for tracing the matrilineal line (your mother/maternal side). Y-Chromosome is for tracing your patrilineal line (aka surname tracing) or your father’s side. These two dnas are for tracing direct descent as these sex-based chromosomes are copied identically from one generation to the next, not half/half as the autosomal dna chromosome’s dna. Correctly, said the mutations in mtDNA and Y-DNA are more infrequent than the non-sex based genome (i.e. autosome) and they are not mixed like the other 22 chromosome’s dna. If you follow the blue arrows (in the diagram) up/down your family tree that is your linear descent; so you mtDNA to trace your mother’s side and use YDNA to trace your father’s side to your proverbial mitochondrial-Eve or your Y-Adam. You are testing for the blue boxes in our diagram.

So what is autosomal DNA?


Inside Red Lines – are autosomal DNA generations.

The autosomal DNA are the dna from the other 22 non-sex chromosomes pairs. Autosomal DNA testing is a genealogical DNA test that uses either autosomal STRs or autosomal SNPs. (STR’s are Short Tandem Repeats; SNPs are single-nucleotide polymorphisms.) However, testing companies do not currently offer autosomal STRs tests that use enough STR markers for genealogy. The preferred choice for both genealogy and ethnic population matching is microarray chips that use hundreds of thousands of autosomal SNPs.

Mathematically, speaking you need at least six generations back before you get enough certainty(99% certainty) to do matching to find distant cousins by using current Genealogical DNA testing. So if you do not have your 4x-great-grandparents’ (all 64 of them) surnames then you are NOT guaranteed to be able to use current DNA tests to determine your relatedness to another genealogist (and his/her ancestors who must also have six generations in their tree too).

I am thinking we are still one or two generations (35-70 years) away from using this as a viable technique that will work with any two random genealogists — mathematically speaking. Obvious exceptions are Icelandiks or Amish or other relatively closed-genetic populations who may have greater success (or counter-intuitively lesser) with fewer generations. Its all in the DNA and in the quality of the testing to catch the diversity in your genome.

You will notice that the fine chart we have been using, including the one with the red-lines (my lines) that indicate autosomal DNA testing candidates, does NOT show enough generations. It would need to be extended one more generation. So we need the surnames of 64 people with whom we only share 1.5675% of our DNA with. That is with direct descent. If we are matching to the autosome DNA  (i.e. our Nth cousin, M-times removed) then we are matching to someone who we may only share 0.0243% blood with. That is 2/100th of 1 percent !

Related Blog Article


p style=”text-align:justify;”>Violinist’s Thumb24-January-2014 – This has many great links to other articles and includes some pertinent facts on DNA to think about. A Guaranteed thought provoker of a blog.


3 Comments to “Genealogy Consanguinity & DNA — #Genealogy #DNA #Kinship”

  1. What do you call this relationship? My 4 X great Grandfather Andrew Montanye had a Daughter named Eliza who married James Sickler. they had a son named Ziba, and Ziba Sickler’s daughter Eliza married John Melvin French, John had a son Myron French.
    Andrew Montanye also had a son named David who married Lovina Newman, they had a daughter name Angeline Montanye, who married William F. Jones, they had a sone named Theodore who married Flora Setzer, they had a a daughter Dorothy Lillian Jones.
    Myron E. French a descendant of the first named Andrew Montanye, married Doroty L. Jones who is also a decendant of Andrew Montanye. (Yes Andrew is a descendant of THE colonists de la Monyanye’s of New Amsterdam NY/ later named New York City).
    So as a result I have twice as much Montanye blood coursing though my veins.


    • Lorraine,
      Thanks for reading and writing. Yeah by the time you get to your 4x great-grandparents and further you find one person in many of the boxes due to re-marriages/leverite marriages, etc. SO you get all kinds of relationships (many of which I cannot calculate). I wonder if there are rules for calculating these relationships.

      My father has a family tree with such complexities and I see calculates their relationship to me in way that I find “non-optimal”. So keep your eyes sharp.


  2. That fellow’s chart is pretty, but I think the math and relationships are wrong. If siblings have the same parents, aren’t all of them fishing from the same gene pool? So, why does the chart show siblings at 50% instead of 100% consanguinity? The same proportion should hold between all siblings, up the line. It also looks as if the relationship labels for the oldest two green boxes have the wrong numbers: at the 4th generation, we have our great-grandparents with our great-great-granduncles/aunts for their siblings, and at the 5th generation, we have our great-great-grandparents with our great-great-great-granduncles/aunts for their siblings.

    Liked by 1 person

Tell Me Your Thoughts ...

Please log in using one of these methods to post your comment: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: