I have had my DNA results from Ancestry.com for about a month now. I can not say that I have had any profound discoveries since investing my $100 in this genealogical research but I have learned an awful lot.
One of the the big lessons has been that people don't understand DNA.
I have tried to correspond with some of the people Ancestry says I have genetic matches with. Many of the response have included phrases like, "we are probably related, but not directly." Um, no. See a DNA match means we are probably directly related; that somewhere, maybe way back in history, we have a common ancestor. Now granted, we may never be able to determine who that ancestor is because DNA has been around a lot longer than Watson and Crick's 1953 publication about the double helix; DNA has been around a lot longer than NEHGS (the New England Historic Genealogical Society, founded in 1845); a lot longer than the first human records. DNA has been around as long as life.
So some of these distant cousin matches Ancestry has provided me with go back much further than human records. An generation is approximately 30 year. My parents were born in the 50s, my grandparents were born in the 1920s, my great grandparents were born in the 1890s; and that is just 4 generations. So when Ancestry indicates that there is a low possibility that I am in the range of being 5th to 8th cousins with someone your talking about maybe having a common ancestor 7 generations ago; people born in the late 1700s, before birth certificates, before death certificates, longer than most church records have survived. We may never know if or how I am related to these low-level certainty distant cousins - - BUT...
...BUT, if I can pinpoint a documented ancestor of mine living in the same community in the 1700s as one of your documented ancestors and the two just happen to shared the same surname, um, that is probably the line through which we are somehow directly related; YES, directly. Maybe our common ancestor is much further back than those two contemporaries but I'd bet that is where our common gene pool resides.
And if you don't think that is possible then, well, I kind of don't understand why you took this test; and furthermore I kind of hope I'm wrong about how DNA works. But guess what? I'm not.
If you have 45 minutes to invest in learning more about DNA, I highly recommend watching this video (http://www.youtube.com/watch?v=lkexKLCak5M); The Human Family Tree.