Wednesday, May 13, 2020

Dear Randy: "Why Don't I Recognize More Surnames of My DNA Matches?"

A genealogy colleague asked me this question, and I have pondered (and mulled!) it over myself.  

Who are these people that may share my DNA?  Why don't I have more DNA matches named Seaver?

I have 67,251 AncestryDNA matches (7 cM or more).  Only 1,477 (2.2%) of those have 20 cM or more shared DNA.  I have about 380 ThruLines (meaning descendancy paths from a common ancestor to me and to my DNA match).  74 of them have 20 cM or more shared DNA - that's only 20% of the ThruLines.

I have 8,390 MyHeritageDNA matches (8 cM or more).  Only 1,257 (15%) of those have 20 cM or more shared DNA.  I have 9 Theory of Family Relativity matches (meaning descendancy paths from a common ancestor or me and to my DNA match).  8 of them have 20 cM or more shared DNA (89% of the ToFR matches).

There are very few DNA matches with the surname Seaver:

*  1 AncestryDNA match has a Seaver surname, but a 7th cousin
*  42 AncestryDNA matches have a Seaver surname in their tree;  

*  0 MyHeritageDNA match has a Seaver surname.
*  1 MyHeritageDNA match has a Seaver surname in their tree.

I am quite sure that I am not unique in this regard.  If my surname was Smith or Brown, there would be more with my surname.  But not hundreds of them.

I think the same holds true for my other surnames of interest - my 8 great-grandparents were Seaver, Richmond, Hildreth, White, Carringer, Smith, Auble and Kemp.  Those are the names that a person like me might be expected to know if asked on the street or in an email.  White and Smith are fairly common.  But perhaps 50% or more of all persons don't know all of their great-grandparents surnames.

If 30 million USA citizens have taken an autosomal DNA test, that's only 9% of the population of the country.  So far, only 2 out of the 30 million testers have a Seaver surname.  I don't know the statistics on the popularity of Seaver as a surname.  Assuming a 330 million US population, if it was 0.001% (1 out of 100,000), there would be 33,000 Seaver persons.  I think it's less than that!

The point is that sharing segments of DNA indicates that we might be genetically related to our DNA match.  Almost all of my autosomal DNA matches share one of my 128 5th great-grandparents.  But my 128 5th great-grandparents were born in the 1700 to 1750 time frame, and they are 7 generations back from me.  If each generation produced the same number of babies per couple, then I would expect that 1/256 (0.4%, or 261 on AncestryDNA) of my matches would have a Seaver surname (allowing that half would be females who would produce babies with a different surname).

There are 6 potential surname changes from each of those 128 5th great-grands to me and my 6th cousin or closer DNA matches.  In addition, many of my 19th and 20th century ancestral families had small families of 1 to 3 children.

So I think it is expected that someone with autosomal DNA matches may not see many surnames that their matches share with their 8 great-grandparents.  

I did a study 19 months ago about the presence and size of the family trees of my first 500 AncestryDNA matches (see  How Many of my AncestryDNA Matches Have Attached Trees?).  

At that time, the study indicated that for my first 500 AncestryDNA matches:

*  No Tree:                                        122 = 24.4%
*  Private Tree:                                    40 = 8.0%
*  Unlinked Tree:                              122 = 24.4%
*  Less than 10 persons:                     38 = 7.6%
*  10 to 100 persons:                          57 = 11.4%
*  100 to 1000 persons:                      65 = 13.0%
*  1000 to 10,000 persons:                43 = 8.6%
*  Greater than 10,000 persons:        13 = 2.6%

Summing up the ones with attached and readable trees, only 43.2% of my AncestryDNA matches even had a public tree, and of those only 11.2% of them had more than 1000 persons in their tree. Another 13% had 100 to 1000 persons in their tree.  And 44% of those with a tree had less than 100 persons in their tree.  

I have more AncestryDNA matches now, and I will bet that these percentages will be even lower!  

This raises my own question of "Why don't I have more ThruLines and Theories of Family Relativity?"

My answers are:

*  Not many DNA testers have a significant family tree back to, say, 5th great-grandparents.
*  Very few family trees have every ancestor listed back to 5th great-grandparents (I don't, I'll bet no one reading this does!).
*  The Ancestry BIG tree (see A Reader's Take on Problems - Part IV: The Ancestry Big Tree), which was created from Ancestry Member Trees, does not have every person who ever lived since, say, 1600, and that is what is used for ThruLines.
*  The MyHeritage set of MyHeritage trees, along  with FamilySearch Family Tree, Geni World Tree and WikiTree, does not have every person who ever lived since, say, 1600, and that is what is used for the Theory of Family Relativity.
*  We need a BIGGER and more complete BIG family tree!

So the answer to my colleague's question, and my own question, is that there are not enough DNA matches with large and deep family trees (say, 1000 profiles or more back to 5th great-grandparents), and not everyone who has lived since 1600 are in those family trees that are available, and no one has put it all together yet.  

What do my readers think?  Am I wrong?  Please tell me your "Theory of the Missing Surnames," or your views on big, collaborative family trees.  I would love to hear them!


Disclosure:  I have a complimentary subscription to and MyHeritage, and use the sites every day.  I have received material considerations from and MyHeritage in years past, but that does not affect my objectivity in writing about their products and services.

The URL for this post is:

Copyright (c) 2020, Randall J. Seaver

Please comment on this post on the website by clicking the URL above and then the "Comments" link at the bottom of each post.  Share it on Twitter, Facebook, or Pinterest using the icons below.  Or contact me by email at


Linda Stufflebean said...

I agree with all the points you've made. I think the top reason might be that many people only took a DNA test out of curiosity or because it was a gift and have never done any fmaiy history research.

Danine Cozzens said...

I'm still in the process of outwitting this situation by searching out all the descendants of all the siblings of my grandparents, then my g-gs, etc. Since these were large families, it's quite a task! But using Ancestry and census and basic BMD matches, it's been fairly straightforward. Then I sit back and let the Ancestry software do the work for me, at least when people have entered parents and grandparents. It also helps have at least the marriages for the sisters of the g-g-g-s -- that way I know immediately when I see a last name that it's probably going to be a match for a certain line.

searchshack said...

Think that to increase your ThruLines, you need to flush out the families of all of your ancestors and their known descendants. Here is how I increased the ThruLines for my third great grandparents. Researched and wrote about them with extensive sources. Looked at all my DNA matches and their shared matches. Then flushed out my trees to include those trees (lots of work as I do a lot of source verification. Then I shared the blogs with those folks in Ancestry Member Connect who had sources in their trees.
After about two months, I went back to my ThruLines and for most of these ancestors the ThruLines had increased by about 30% -- think Ancestry found more family connections with smaller partial trees. The increase is not equally as it does seem that some families seem to do DNA testing in groups.
Two more third great grandparents to go, then onto my fourth great grandfathers!