While DNA passes from parent to child, each child only gets half of each of their individual parent’s DNA. Consequently, as a lineage is worked back in time, there will be ancestors in your genealogical tree with whom you might not share any DNA. It doesn’t mean that the ancestor is not your ancestor. It simply means that their DNA did not makes it’s way all the way down to you. While DNA is microscopically small, there’s only so much your body needs.

Some suggest (for example, Blaine Bettinger in his  The Family Tree Guide to DNA Testing and Genetic Genealogy) that once a lineage is traced back to the 4th great-grandparents that there are paper genealogy tree ancestors with whom you do not share DNA.  That’s why you may share no DNA with another descendant of one of your 5th great-grandparents.

Of course there have to be ancestors in your tree with whom you do share DNA.



6 Responses

  1. I have a mystery grandfather that through DNA I have a good idea who it may have been, but likely will never be able to prove by paper. He is dead and had no other children that I have found. How do I handle that? Do I just make a footnote/asterisk on my suspicions?

  2. I have a couple sets of 5th great grandparents in which I don’t have any DNA matches. Thanks for the post. It confirms that this is possible.

    • It also depends on how many other descendants of that couple have tested, but I have several relatives from ancestors this far back who have tested and who are DNA matches with me.

  3. Very true. I have DNA ancestors that have appeared to contribute DNA as far back as 8 generations, then I have lines where DNA matches stop at 6 generations. It’s all very interesting.

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