The short answer is we haven't found anything definitive yet.
Three individuals from this group have taken the autosomal test (that I know of) offered at Ancestry and all show European Ancestry.However, since you lose half of your potential DNA from your parents, once you go back about 7 generations, the amount of DNA you still have from any one of your ggggg grandparents is less than 1 %.Since the non European ancestor is probably back several generations prior to this, you can see the problem.
At Family Tree DNA, where the Vinton County Group Project is located, it's a little bit different. We have the results of a YDNA test for the descendant of Holman Thacker.This is a father to son transfer of DNA, so it only shows one line of an individual's DNA.In this case, the Haplogroup is R1bi which is of European origin.(Because of other DNA information too complicated to go into we know that this individual's origins are mostly likely in the British Isles).
The interesting part is that there were matches to this individual's DNA already in the Family Tree DNA database, but they were not Thacker matches as you would expect.The match was found in the Gibson Surname project, specifically the descendants of Gilbert Gibson.In other words, the genetic surname for Holman Thacker line is Gibson not Thacker. Without other Thackers from Vinton County taking the test we don't know if this is true of all of our Thackers, some of our Thackers, or if this only pertains to Holman Thacker's line.
We have 3 individuals who have taken the mitochondrial DNA (mtDNA) test. Each of us has mitochondrial DNA but only women can pass it to their children.This is very stable DNA that does not mutate rapidly, so that even if you find an exact match from taking the full sequence test it only means that somewhere in the past 400 years, you have the same ancestress.
A descendant of Mildred Jane Thacker (wife of Wetherfoot Napper) took the test and her Haplogroup is H1c.The H haplogroup is the most common mtDNA Haplogroup found in Western Europe. H1 (a subgroup of H) is found in 10% of France, British Isle etc Population - the highest concentration, almost 28%, is found in the Basque population. There were five individual's who were an exact match, and we have yet to discover (and may never discover) the common ancestress.
The other two who took the mtDNA test were a descendant of Ann Thacker (wife of Levi Napper, daughter of David Thacker and Sally Lemay Thacker) and a descendant of Frances Thacker (wife of Nimrod Nicholas Thacker).Ann had only one exact match in the entire Family Tree DNA database - that of the descendant of Frances Thacker, meaning that Ann and Frances have a common ancestress.Which means they could have the same mother, or they could have the same grandmother, or they could have the same great grandmother etc.
Their Haplogroup is U3a. U3 is found in Europe and in Western Asia.It is mostly found around the Black Sea area (think Bulgaria, Georgia, Romania, Turkey, Syria, Jordan, the southwestern area of Russia etc.) It is very rarely found in Western Europe - less than .5%
As more people take part in these tests (and I hope some decide to take the test), we will be able to find more answers to the puzzle of the Vinton County Group.
If you or your friend have any more questions, please feel free to contact me.