Monday, April 2, 2012
"Finding Your Roots with Henry Louis Gates Jr." - DNA in The Third Episode
Last night PBS aired the third episode of Finding Your Roots with Henry Louis Gates Jr. which featured journalist Barbara Walters and educator Geoffrey Canada. The episode revolved around investigating the guests' paternal roots by tackling the challenges of discovering the original surnames of their fathers' ancestral lines. Geoffrey's was obscured mostly due to his extremely limited knowledge of his father's family. Although Barbara had previously had her family tree researched, her immigrant ancestor's name change had not been discovered.
After discovering that Geoffrey Canada's paternal line was descended from Thomas Cannaday, a slave owned by a Charles Cannaday of Franklin County, Virginia, Geoffrey's Y-Chromosome DNA was analyzed to determine if his great-great grandfather Thomas may have been fathered by his slave owner. Not surprisingly, Canada does possess a European Y-Chromosome Haplogroup. In fact, he apparently shares his haplogroup with Kevin Bacon, Robert Downey, Jr. and Harry Connick Jr. Since the majority of men in the Bacon DNA Project, the Downey DNA Project and the sole man in the Conrick DNA Project (possibly a variant of Connick) possess the R1b1a2 Y-Haplogroup (the most common in Europe), it is likely that Geoffrey's Y-DNA Haplogroup is also R1b1a2. This piece of information is not enough to solve the puzzle though, since there is no way to know for sure when that European ancestor entered Geoffrey's direct paternal line, so Dr. Gates' team identified two great grandchildren of Charles Cannaday and asked them to take an autosomal DNA test to determine if their great grandfather is the same man as Geoffrey's 3rd great grandfather. If the working theory was correct, that would mean that these Cannaday descendants are Geoffrey's 2nd cousins twice removed and would be expected to share about .781% of their DNA (the same amount as third cousins). In this case, there is a chance that the autosomal test could be ineffective due to the fact that only about 90% of third cousins have enough shared DNA to be detected by this kind of test. Although it would certainly be worth a shot, this scenario could be stretching the capabilities of autosomal DNA testing just a bit. Even if they were to have a small amount of shared DNA, without extensive testing of other descendants, it might be difficult to say with certainty that the DNA came from this potential shared ancestor rather than another, especially since we know both families' ancestors lived in the same geographical area. In my opinion, a Y-STR DNA test on Charles Cannaday's direct paternal descendants (or his father's, uncle's or brothers' direct paternal descendants) would be more conclusive because it would determine if Geoffrey is carrying a Cannaday Y-Chromosome or not. Unfortunately, the theory did not get to be tested anyway because, in the end, both of the Cannaday descendants identified by Gates' team declined to participate in DNA testing. Dr. Gates, with deadlines looming, was probably forced to leave the question unresolved for now. Many of us genetic genealogists know how it feels to track down the perfect candidate to test out a genealogical theory, only to find that the person identified is unwilling to take a DNA test. It is always disappointing, but given the luxury of time, perhaps his team wouldn't have stopped there. Since the local Cannaday researcher said that she had 3200 Cannadays in her database and that it was still a very common name in the area, the team could have either looked for descendants of Charles Cannaday's father or asked his great great grandchildren to test. (I have found the younger generations are often more willing.) In either case, the potential relationship to Geoffrey would have been one more step removed, thus decreasing the chances of a match even further, but still worth investigating.
Obsessive genetic genealogist that I am, I just couldn't let the Y-STR idea go, so I searched for a Canada/Cannaday DNA Project to try to determine if there were any Cannadays already tested, against whom Geoffrey's Y-STRs could be compared. I was initially surprised to find that no project of this name exists, however I did find a Kennedy DNA Project that lists variants Canaday and Canady. Upon further investigation, I found that there are 15 Canadas, 12 Canadys, six Cannadys, seven Canadays and one Cannaday who have tested at Family Tree DNA (they may not all have taken a Y-STR test). If you look at the Kennedy DNA Project's Results Page, you will find some of them there. There are seven participants of interest - four named Cannady, one Canady, one Canaday and one Canada. Six of these seven fall into the haplogroup R1b1a2. (The one who does not is identified as being descended from a Charles Canaday, but there is no information supplied as to birth or location.) It may be that none of these are directly descended from the direct paternal line of Charles Cannaday of Franklin County, Virginia, but just for kicks, it would be interesting to see if Geoffrey's Y-STRs match any of these participants. I wonder if Dr. Gates' team investigated this avenue.
Like last week, geneticist Joanna Mountain from 23andMe appeared on the episode - this time to explain the Y-DNA analysis. Interestingly, in this segment there appears to be two spots where there are inaccuracies in regard to this DNA test. The first one occurs starting at 41:15 when Dr. Gates asked Dr. Mountain, "So a Y-DNA analysis, in other words, is what people in the barber shop talk about the paternity test?" and she (appears to have) answered, "It sure is." The exchange seems awkward and I believe this mistake was made in editing. I am sure that Dr. Mountain would never imply that a Y-DNA test is the same thing as a paternity test since it unquestionably is not. (I think what happened is that her comment was not actually in response to that questions, but was pasted in from another part of the segment.) A traditional paternity test is based on autosomal STRs markers, like CODIS . While it's true that a Y-DNA test could informally be used as such, in reality it cannot tell us if two people are father and son, only that they come from the same direct paternal line. (They could actually be brothers, uncle/nephew, first cousins, second cousins, etc...) The second mistake was probably merely a slip of the tongue on the part of Dr. Gates, but still worth clarifying since genetic genealogy is so new to many of the viewers. Starting at 43:35, Dr Gates explained what the results of this Y-DNA test mean for Geoffrey, "We do know without a shadow of a doubt that a white man fathered your female slave ancestor [bold mine] and entered your family line." I'm sure he meant to say "impregnated your female slave ancestor" since it was actually Geoffrey's male ancestor that was fathered by a white man. We know this because the Y-DNA only follows the direct paternal line. By definition, women cannot be introduced into this line because they do not inherit a Y-Chromosome. I don't mean to call anyone out on these mistakes, but I do think it is important to explain and clarify in an effort not to confuse any viewers new to the concept of genetic genealogy.
The next time DNA was mentioned in the episode was when Dr. Gates asked Barbara what percentage of her DNA she thought was of Jewish origin and she guessed 99.9%. An admixture test, which appeared to be FTDNA's Population Finder (included with the Family Finder test) revealed that she is actually ~91% Middle Eastern (Jewish) and ~9% European (non-Jewish). Dr. Gates noted that this exercise with Barbara illustrated that DNA analysis is revealing that "our family trees are more diverse than we had assumed."
This concept is proving true for African Americans as well. "In the African American community, genetic evidence of our rainbow-colored roots is challenging long-held assumptions about what it means to be black," Dr. Gates explained. To illustrate this, reminiscent of last week's scene in the barber shop, Dr. Gates asked several students from Geoffrey's school to estimate how much of their DNA is African, European and Native American. After swabbing their cheeks, the students were surprised to find from their admixture tests (which appeared to be from 23andMe) that their ancestry was more diverse than they first imagined. After learning that a portion of her DNA was European one student said, "I didn't know that I was European.. now I don't consider myself just black." Gates emphasized that these tests "deconstruct the notion of race" and reveal that "we are all mixed up".
I'm very pleased that DNA was again a vital component of this episode, but a little disappointed that they weren't able to use it more conclusively to determine Geoffrey's paternal ancestry. I guess that is realistic though and better than implying that genetic genealogy is always easy. By the way, can you believe Barbara Walters is 82?! She must have some pretty darn good DNA! I thought it was kind of funny that her family's original surname Waremwasser sounded an awful lot like Gilda Radner's Baba Wawa. I look forward to next week's episode with Kevin Bacon and Kyra Sedgwick. I hope they perform autosomal DNA tests on the couple to see if Kyra's fear is true and they are indeed "kissing cousins". See you then!