The Theory of Autosomal DNA Matching

You have seen the basic theory behind y-DNA matches and mt-DNA matches. Briefly the Y chromosome changes minutely about every fourth generation, as you can see by comparing 67 marker results from the same male lineage. In actuality it is a matter of statistical probability and the minor change may have occurred just between the last two generations, or it may have been six generations ago. The usefulness of using the Y chromosome for matches is to learn more about a male line of descent. The mitochondrial DNA changes much less frequently. It changes at about 1/10th the rate of changes in y-DNA. Thus it is of less genealogical help when fine-tuning recent generations of a family line, but can definitely establish a connection to an historical maternal line. (For more on y-DNA or mt-DNA see previous Taylor blogs.)


Autosomal DNA which is tested through as “Family Finder” at www.ftdna.com, is entirely different. This test looks at segments of the non-sex determinate chromosomes and compares matching segments throughout the Family Tree DNA database.

Here is the theory behind this test. Each of us has received our genes from our biological forebears. Each time a new human is created, some genes from each parent are combined and some are not included. Approximately ½ of our autosomal genes come from each of our parents. Each of them received half of their genes from each of their biological parents.

To simplify our understanding we are going to consider these blocks of genetic material as playing cards. Imagine you are holding a hand of cards—8 cards—and each card represents a unique inheritance from one of your great-grandparents. From Great Grandmother Susie you got the Ace of Spades, for example. But you have 8 cards and one is from each of your great-grandparents.

Let’s follow that Ace of Spades backwards in time. Great-grandmother Susie received it from one of her great-grandparents. And that great-grandparent received it from one of his or hers…

Now back to Great-Grandmother Susie. She was part of a large family. Let’s say there were ten children. Maybe half of those children, Susie’s siblings, got that Ace of Spades in their genetic package. Those of Susie’s siblings who reproduced gave their children part of their genetic heritage. For many it may have included the Ace of Spades, but probably not for all.

Now consider again the hand of cards you received as your birth package of DNA. You got the Ace of Spades (which is a simplified way of saying you got a unique segment of DNA). Anyone else in the Family Tree database who also has the Ace of Spades is a cousin to you. Their relationship may be as far back as seven generations, or more! However we know that you are biologically/genetically related individuals. Now the practical aspects of using this autosomal testing method, Family Finder, become of interest. We will take up that topic in a future blog.

Lalia Wilson for the Taylor Surname Project

Lalia is keenly interested in genetic genealogy for many reasons, among them the many common surnames in her personal genealogy. In addition to Taylor, these include: Jackson, Johnson, Madden, Moore, Robinson, Stone and Wilson. These families were in North America prior to 1700 and followed migration paths from Virginia or Pennsylvania or New York to Ohio then Missouri or to Kentucky then Missouri. Please contact Lalia with questions about the blog, or story ideas, or if you think you’re a relative: Lalia W /at/ aol dot com.

Sale on genetic tests!

Greetings fellow Taylor fans!  If you have been putting off genetic testing because it's too expensive, order your tests today.  If you've ever wanted to do genetic genealogy there has been no better time than today.

We at the Taylor project can also probably be of some help with Family Finder, y-DNA or mt-DNA results and matches, if you want our help. We are your first choice for the Y-DNA, of course, but some of us have done a bunch of work on the other tests, too.


The site www.ftdna.com is the place to go. They have by far the biggest database--about 10 times what's available elsewhere--and the focus is on genealogy, which is not necessarily the case at other sites.

For Y-DNA, do 67 markers or more. A 67/67 match means that the men are related (50% probability) no further apart than second cousins. You are wasting time and money to test fewer than 67 markers. (A 12/12 match means you are related in the last 2,000 years! Not much genealogical help.)

I recommend you also do a Family Finder test that tests all family lines on autosomal DNA. This will even be of help assuming you are a male Taylor wanting information only about the Taylor line.  Why?  Because one of your cousins, not a Taylor direct descendant, may have that critical missing piece of information about your Taylor line.

If you want to do mt-DNA, go ahead. So far my brother and I have no matches there, but we do know we are haplogroup T2, the same as many of the deceased in 79 AD in the Vesuvius eruption, and the same as Czar Nicholas II.

Lalia Wilson for the Taylor Surname Project


Lalia is keenly interested in genetic genealogy for many reasons, among them the many common surnames in her personal genealogy. In addition to Taylor, these include: Jackson, Johnson, Madden, Moore, Robinson, Stone and Wilson. These families were in North America prior to 1700 and followed migration paths from Virginia or Pennsylvania or New York to Ohio then Missouri or to Kentucky then Missouri. Please contact Lalia with questions about the blog, or story ideas, or if you think you’re a relative: Lalia W /at/ aol dot com.