I like ahnentafels!

If you started doing genealogy back in the olden days, as I did, you probably used ahnentafels. They are a simple way to number your direct ancestors.  Ahnentafel numbering can be useful in our DNA notes too!

In genealogy presentations, I sometimes include a screen capture that includes an ahnentafel number, and then participants want to know what that means. So this month, I offer a short post about that.

Wikipedia describes it thus: “Ahnentafel, also known as the Eytzinger Method, Sosa Method, and Sosa-Stradonitz Method, allows for the numbering of ancestors beginning with a descendant. This system allows one to derive an ancestor’s number without compiling the list and allows one to derive an ancestor’s relationship based on their number.

The number of a person’s father is the double of their own number, and the number of a person’s mother is the double of that person, plus one. For instance, if the number of John Smith is 10, his father is 20, and his mother is 21.”

For an illustration, see Image 1.

Image 1.

ahnentafel sample

The start individual, male or female, is number 1. That person’s father is 2.  (Any person’s father in the chart is always twice the number of his child. So, 2’s father is 4. The father of 7 will be 14, etc.)

A child’s mother is always the child’s father’s number + 1. So, if I am 1, my father is 2 and my mother is 2+1=3. If my dad is 2, then his father is twice 2, or 4. My dad’s mother is 4+1=5. Other than #1, even numbers in an ahnentafel are always men/fathers, and odd numbers are always women/mothers.

Let’s take it backwards too. Who is number 13? It’s always the wife of 12, who is the father of 6, who is the father of 3, who is the wife of 2, who is the father of 1. So if I am #1, then #13 is always my mom’s paternal grandmother. (If this method of numbering is new to you, follow along with the chart and let it sink in a little.)

An ahnentafel is very streamlined. Its rules address only direct ancestors, and they don’t consider multiple marriages or siblings or cousins or many of the more intricate relationships we may explore in our families. But an ahnentfafel does have value–especially for DNA, since those DNA segments can only come to us from those direct ancestors.

For genealogy in general, it gives us a space-saving means to simply list all our direct ancestors in a meaningful order. But I like to use it in my DNA record-keeping too.

Image 2 is an excerpt of how I label the ancestors from whom I inherited certain chromosome segments mapped in DNApainter.com. (You don’t need to include ahnentafel numbers; I just like to! In the key to the right, I first have them sorted by grandparent: green is paternal grandfather’s line, yellow is paternal grandmother’s lines, blue is maternal grandfather’s lines, and red is maternal grandmother’s lines. Within each of those, I sorted by 3-digit ahnentafel number of the direct ancestor who passed that DNA segment down to me.)

Image 2.

ahnentafel in DNApainter

I also use ahnentafel numbers in my spreadsheets and documents for MRCA (Most Recent Common Ancestor) related to a specific cousin or DNA segment. If space is an issue, it takes up a lot less space to enter ’15’ than to enter ‘Magdalena Dorothea Kostmerchock’.

I like to use it in my AncestryDNA notes area too. With the MedBetter chrome extension, I can filter my matches to see only those I’ve marked with a specified hashtag. In Image 3, you’ll see I have two 4th cousins. One has MRCA spelled Dorsey-Tinnon, the other has MRCA spelled Darcy-Tynan. The families had used inconsistent spelling. But I can filter based on the ahnentafel number of our Most Recent Common Ancestors and find both of them.

Image 3.

ahnentafel in MedBetter

If I am looking at an ancestor I’ve identified as #56, I always know exactly who he is: he’s the father of 28, who’s the father of 14, who’s the father of 7, i.e. the wife of 6, who was the father of 3: my mother. So MRCA #56 is my mom’s maternal grandfather’s father’s father. (It takes up a lot less space to just enter #56!)

You may find places in your genealogy or DNA match data to use ahnentafel numbering too!

Ann Raymont (c) Oct 2018

3 thoughts on “I like ahnentafels!

  1. smpfamily

    An excellent suggestion! Especially since my ancestors spelled their names differently in different records in different languages in different countries, and my matches’ names are often spelled differently for the same people!

    Liked by 1 person

  2. Deborah

    Thank you! I’ve been seeing this around for months, and ignoring it because I had a misconception about how it worked! This is a great explanation, and heck yeah, it’s a great idea!



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