The Y chromosome test (that only men can take) has certainly been the "gold standard" over the years. That test is "representative" of the male donor's father, his father's father, his father's father's father, etc. etc. So....if the male DNA donor is a Mr. Jones, for example, then the Y chromosome DNA test result would typically be "representative" of his entire "Jones line." The "monkey wrench" that can be thrown into this test (and into any other DNA test), however, is if there was a "non-paternity event" (i.e., an adoption or an out-of-wedlock birth), somewhere in the donor's line. For example, my mother (who was born a Miss Brown) had a male cousin who is a Mr. Brown, but his Y chromosome DNA test results were a match to only three men who are all Mr. Smiths. We now know that my maternal gg-grandfather named Smith W. Brown was actually an "Smith infant" who was taken-in, named and reared by a Brown family in Middlesex Co., VA (hence, my mother was actually a "biological Smith" versus a "biological Brown"....though she went to her grave in 1997 without knowing that).

The mtDNA test (which can be taken by a man or a women) is "representative" of the donor's mother, that mother's mother. that mother's mother's mother, etc. etc. While similar in concept to the Y chromosome test, the results from this test present a much harder challenge to research. That is because every time a woman marries, she receives a different last name. For example, my mother was a Miss Brown/Mrs. Davidson, but her mother was a Miss Roudabush/Mrs. Brown, while the mother of this last woman was a Miss Messick/Mrs. Roudabush. So....it can become quite complicated to "use" the results of this test (plus, a lot of people have no idea what the maiden name of their mother's mother's mother's mother was, for example).

The third popular DNA test is called the "Family Finder" test by Family Tree DNA, and other companies like "Ancestry" and "23andme" have a similar test. This test can be taken by a man or a woman, and it will basically show "DNA matches" to people (who have also taken this same test) who share any common MALE or FEMALE ancestor with the donor within the last four or five generations (this test apparently can provide some "false positives"....and/or omit relatives all together....once you go back more than about four or five generations). People who take this test frequently have hundreds of matches, since all kinds of male and female cousins can "appear" (with a variety of last names). So....this test can be even harder to "interpret" than the mtDNA test....but is has still proven to be very valuable to some researchers. As an example of the difficulty, one of the donor's "matching" relatives (who also took this DNA test) could be a Mrs. Jones/Miss Smith, for example, but the REASON that the donor is a match to that Mrs. Jones/Miss Smith could be because both donors share a "common Brown relative" from a few earlier generations....plus that "common Brown relative" could have been on either donor's father's "side of the family" or on the mother's "side of the family"....so you can image the effort it can take to "make sense" of the results from this test.

I took the 37 marker Y chromosome test at Family Tree DNA, and I have six other men named "Davidson" at this time who are an "excellent DNA match" to me....and I now know how every one of them connects to my "Davidson line" (and I have similar DNA test results for the above-mentioned Smith/Brown family). I have "traced" all three of these surnames (Davidson, Brown and Smith) to men in those families who were in Virginia in the 1600s.

Comments/questions?

Bill

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