My friend Tony Givens asked me how the heck I obtained the YDNA of my great-great-great-great grandfather Samuel Rankin, who I had identified as my ancestor via YDNA testing. Did we exhume his corpse, or what?
I was initially at a loss how to respond.
The short and almost correct answer is that I obtained Samuel’s YDNA by persuading my cousin Butch Rankin to take a YDNA test. However, I knew that wouldn’t suffice. Instead, I fell back on a standard cross-examination technique, asking leading questions to which I already knew the answer … hoping to answer Tony’s question without delivering an impenetrable lecture.
“So … tell me Tony, you know who your Givens grandfather is, don’t you?”
“Sure,” he said, “his name was David Givens.”
“OK,” said I, “you know the name of David’s father, right?”
“Yep! Harland Givens was my great-grandfather.”
“Well, Tony, if you swab your cheek today for a YDNA test, what would you have?”
Tony looked nonplussed. “A sample of my YDNA?”
“Yes, indeed. You would also have the YDNA of Harland Givens, give or take a few marker values.”
“Can’t be,” said Tony, “he’s been dead for a century.”
At that point, there was no alternative but to deliver a pseudo-scientific lecture about YDNA theory. A short summary follows. I am qualifying it as “pseudo”-scientific because I’m not a scientist and it’s easy to oversimplify these matters. Someone who actually knows something about this stuff may be compelled to post a corrective comment. Bobbi, I hope it will be you. Here goes …
I am female and don’t have a Y-chromosome. Instead, I have two X-chromosomes. Tony, a male, has one X-chromosome and one Y-chromosome. The X and Y are called the “sex chromosomes” because they determine gender. Tony can only have inherited his Y-chromosome from his biological father, since his mother didn’t have one to pass on. Likewise, Tony’s father inherited his Y-chromosome from his father David, who inherited his Y-chromosome from his father Harland Givens, and so on, theoretically ad infinitum up the male Givens line. (This ignores a possible “non-paternal event,” see below).
Those inherited Givens Y-chromosomes could all be identical, in theory. Putting it another way, a male’s Y-chromosome is passed down unchanged from father to son for generation after generation — except for occasional random mutations. If there were no mutations, Tony’s Y-chromosome would be an exact copy of the Y-chromosome of all of his male Givens ancestors.
Thus, the almost correct answer to Tony’s original question was that I obtained my ancestor Samuel Rankin’s YDNA by getting my cousin Butch Rankin to YDNA test. That isn’t quite accurate because mutations have occurred in the intervening generations between Samuel and Butch. If there had been no mutations, then Butch’s Y-chromosome would exactly match his five-great-grandfather Samuel’s.
There is an occasional “oops” in this process, when a man’s Y-chromosome doesn’t match his apparent father’s. This is called a “non-paternal event,” and please don’t get me started on the weirdness of that label. For example, if a male child is adopted, the adopted son inherited his Y-chromosome from his biological father and wouldn’t match his adoptive father. Likewise, if Mrs. Givens were raped and bore a son as a result, the child’s Y-chromosome would be a copy of the rapist’s rather than Mr. Givens’. The same would be true if Mrs. Givens had a son as a result of an extramarital affair.
Except for such non-paternal events, the Y-chromosome follows the line of the male surname without change other than occasional random mutations. This simple fact has given rise to surname DNA projects, in which participants compare their YDNA to other men having the same surname. Women cannot YDNA test, since we have two X-chromosomes. Instead, we cajole our fathers, brothers, sons, uncles and male cousins into swabbing their cheeks for a YDNA test.
There is a potload more science about this, but I’m already in over my head. If you want to learn about STRs (“short tandem repeats”) or SNPs (“single nucleotide polymorphisms”), check out the FAQs at the Family Tree DNA website. Better yet, go search Roberta Estes’s website, “DNAeXplained – Genetic Genealogy.” She does an excellent job of making the science comprehensible.
Let’s leave the science and turn to how YDNA testing can be helpful in family history research.
As one example, it can help an adopted son identify his birth father when all other avenues have failed. I have a friend with a remarkable story who has done exactly that.
For another example, let’s assume that six men having the surname Willis have done 67-marker YDNA tests and joined the Willis DNA project. They are all a very good genetic match, having only one mismatching marker out of 67 between any two of these six men. FYI, the number of mismatched markers is referred to as “Genetic Distance,” so any two of them would be considered a “67-marker match, GD =1.”
Five of the men can trace their Willis ancestry with a high degree of confidence back to a John Willis who came to Maryland from the U.K. circa 1700. The sixth man cannot identify a Willis ancestor earlier than 1800. Fortunately, his extremely close genetic match to the other five men makes it a virtual certainty that they share a common ancestor fairly recently, three centuries being “fairly recent” in genetic time. He would be justified in concluding that he is also descended from John Willis of Maryland.
YDNA testing can also disprove relationships. That leads us to the famous Rankin legend inscribed on a bronze tablet in the Mt. Horeb Presbyterian Cemetery in Jefferson County, Tennessee. You can read the entire inscription concerning this interesting piece of family lore in this article.
The Mt. Horeb tablet says this, elided to focus on relevant information:
“William Rankin had … sons, Adam [and] John … Adam married Mary Steele … John … had two sons, Thomas and Richard, and eight daughters.”
If you have read the Rankin articles on this blog, you know that an Adam Rankin of Lancaster County, Pennsylvania who died there in 1747 did, indeed, marry a Mary Steele. You also know that a John Rankin who died in Lancaster in 1749 left a will naming two sons, Thomas and Richard, and eight daughters.
In short, the Mt. Horeb tablet legend says that Adam Rankin (wife Mary Steele) and John Rankin (sons Richard and Thomas) of Lancaster were brothers.
Six descendants of the John Rankin who died in Lancaster in 1749 have YDNA tested and belong to the Rankin Family DNA Project. They are a close genetic match, and their ancestry “paper trails” are solid. All six are descended from John’s son Thomas.
The Rankin Project also has two participants who apparently descend from Adam Rankin and Mary Steele. They are a 67-marker match with a GD = 5, which is not a very close match. The odds are only slightly better than even that they share a common ancestor within the last eight generations. One man’s “paper trail” back to Adam and Mary Steele Rankin is good as gold. The other man’s chart has one weak link, although it is supported by convincing secondary and circumstantial evidence. It is possible (although unlikely, in my opinion) that these two men do not both descend from Adam and Mary, and, instead, their common ancestor is on the other side of the Atlantic.
In any event, the two men who probably do descend from Adam and Mary Steele Rankin are not a YDNA match to the six men who descend from John. A reasonable and perhaps inescapable conclusion, based solely on the available genetic evidence, is that John and Adam Rankin of Lancaster were not brothers. Perhaps, you may say, they had different mothers? It doesn’t matter from whom they inherited their X-chromosomes, though. We are dealing with Y-chromosomes here, and the YDNA of their descendants says that John and Adam did not have the same father.
This has implications further up the ancestral line. Both sets of descendants believe that Adam (or John) was a son of a William Rankin, and that William was a son of an Alexander Rankin. Based on the limited genetic evidence available, they cannot both be correct. Evidence in actual records about Adam or John’s parents would be wonderful, but I don’t know anyone who has found any.
Whatever is correct about William and Alexander, we need to find another descendant of Adam and Mary Steele Rankin to YDNA test and confirm the above conclusions. We also need to find a descendant of Richard, son of John, to confirm John’s line.
Is there anyone reading this who has a male Rankin relative who hasn’t tested? For heaven’s sake, woman, throw him down on the floor and swab his cheek! Even if he isn’t descended from Adam and Mary, or from John’s son Richard, the results of his test will almost certainly help him (and probably others) learn more about their Rankin family history.
Seriously. Whatever your surname may be, if you are interested in your family history, please purchase a YDNA test (if you are a male) from Family Tree DNA. For the record, I’m not on the FTDNA payroll. It is the only firm offering YDNA tests. Start with a 37-marker test. If price isn’t a problem, do the 67-marker test. You can always upgrade to additional markers later without having to test again. If you have any reservations, contact me via a comment and let’s talk.
Meanwhile, I’ll be out there looking for another descendant of Adam and Mary … and a descendant of John’s son Richard …
See you on down the road.
 There is a spectrum of gender identity from male to female that involves questions beyond both the scope of this article and my expertise. I’m using “male” and “female” as though those are the only options, which is an oversimplification.
 A “marker” is a Short Tandem Repeat. I think. They are what get measured or counted or something in a YDNA test.