From what I have learned most of that is just wishful thinking or clever marketing. The DNA tests used for genealogy purposes will ID someone who shares a common ancestor with you but it does not tell you who the ancestor is or if they lived 100 years ago or 10,000. With the way man has migrated it could be a common ancestor on just about any continent.
I have been tested for the Green surname project at FamilyTreeDNA. It didn't come up with any exact matches but gave me two guys who were matches on 24 out of 25 markers. What does that mean? Not sure. Maybe we have a common ancestor or maybe not. Neither of them could give me any information about their family prior to 1820 which is where my Green family documentation has hit a wall. Maybe one day someone else will submit a test and have a match from an old family bible or some other record, to a John Green, born in 1820 in either South or North Carolina and it will tell me where my Greens came from.
I actually started a Fulford family DNA testing project for my Mother's family, which has already found several family matches with just 10-15 participants.
Why would anyone want to do this? Well a Fulford cousin gave me the following explanation.First an explanation about Y-DNA testing. Y-DNA testing is a new tool for the genealogist or anyone interested in family history. The Y chromosome is passed from father to son virtually unchanged over the generations. This means only males can be used for this particular DNA test.
A kit is sent to the donor's address for the DNA sample. It's a cheek swab. Like brushing your teeth. Simple and painless. Mail back to the lab, and tests are then run. It takes about 6 weeks to get your results.
Test results establish "marker" numbers. These numbers are compared to other donors and when a match occurs, it is proof positive the two donors have a common ancestor. It's that simple.
Here are the top ten reasons to join (or have your male Fulford spouse, father, brother or cousin join) the Fulford Y-DNA Testing Project:
(1) Each donor represents their particular line in the Fulford Y-DNA Testing Project. Years from now, descendants of your family line will be glad you joined.
(2) With a match(s) of Y-DNA to other Fulford participant(s), the donor(s) will know proof positive they share a common ancestor. The test results don't name the common ancestor, but can predict how many generations back he lived. The more markers tested, the closer the prediction.
(3) Matches of Y-DNA between donor(s) confirms your family lineage. You have proof you are related to others with the Fulford name around the world.
(4) The donor will learn the "Recent Ethnic Origins" = Country where his ancestors lived before coming to the USA. Mine is the United Kingdom.
(5) The donor will learn the Haplogroup of his ancestor. This is his ancient ethnic origins. Mine is Nordic (Vikings).
(6) The donor will receive a certificate from the lab showing his Y chromosome marker numbers. If you wish, you may add your markers to any DNA databank. There are 4-5 of these with over 200,000 test results on file. Your privacy is guaranteed. Only you can allow your name and/or test results to be shown anywhere.
(7) The donor's DNA sample will be stored by the lab 25 years at no extra cost.
(8) The donor's marker numbers become a part of the Fulford Y-DNA testing project. Hopefully enough will join so that various Fulford lines of descent will become established for the benefit of current and future Fulford researchers.
(9) The donor's lineage will be added to the Fulford DNA website. This is free advertising for the donor's family line, so that present and/or future researchers/cousins might be able to contact each other.
(10) Test results (marker numbers) will last forever, so it's a bit of immortality. Trouble is for those who haven't joined yet, you aren't getting any younger.