"Finding Your Roots with Henry Louis Gates, Jr." - DNA in the Seventh Episode

The seventh episode of Finding Your Roots with Henry Louis Gates, Jr., featuring Samuel L. Jackson, Condoleezza Rice and Ruth Simmons aired on PBS last night. All three of these African Americans had heard rumors that they had European ancestors, but had never had the opportunity to investigate the truth behind this until Dr. Gates asked them to participate in this series. While this episode's focus was on these notable Americans, it was very much Dr. Gates' story too, so bits of his own journey were interwoven throughout the episode.

Dr. Gates

Very early on in the episode, Dr. Gates informed us that he would be using DNA to help trace both the European and African roots of his guests. I was not disappointed with the role of genetic genealogy in this episode, although I would always like to see the science used even more extensively than is possible in this hour format. I thought it was a bit confusing following so many stories at once, so I had to take some time to really study the episode before writing this post.

The first DNA portion dealt with the question of Dr. Gates' own oral family history that told of his direct paternal line descending from a white man named Samuel Brady. His genealogy team was able to track down a direct descendant of Samuel Brady in order to compare their genomes. Since Samuel Brady was Dr. Gates' presumed great great grandfather this means that the team optimally needed to find a descendant of Brady who was one generation closer to him. This is because only approximately 90% of third cousins (which is what they would be if this Brady descendant was the same generation as Dr. Gates) will share enough DNA from their shared great great grandparent to be detected as a genetic match. If they were unable to find a great grandchild of Samuel Brady, another option would be to use Dr. Gates' deceased father's DNA (I'm assuming they still have some in storage) in the comparison or to also test other siblings and/or cousins from Dr. Gates' family who descend from the same paternal line. I am not sure which route they used, but since Dr. Gates consulted with the illustrious geneticist Dr. George Church on this segment, I am confident that there can be no doubt in their conclusion that Dr. Gates is not a descendant of Samuel Brady.

Dr. Gates non-DNA match with the Barber descendant

Dr. Gates' voiceover mentioned another DNA test that he used in this quest, "Another test proved that whoever this man [his direct paternal great great grandfather] was, he was most probably of Irish or Scottish descent." Although not elaborated on in this episode, Dr. Gates is referring to a Y-STR test that he had performed on his Y-Chromosome DNA. In this test a male is able to discover information on his direct paternal ancestral line's origins. In Dr. Gates case, his Y-DNA fits into the Ui Neill Subclade thought to descend from an Irish King named Niall of the Nine Hostages. More details on Dr. Gates search can be found here. (This type of test can be performed by Family Tree DNA.)

The brief conversation between Dr. Gates and Dr. Church yielded a few very helpful quotes for those struggling to understand autosomal DNA testing that I would be remiss not to transcribe here. First he corrected a popular misconception by mentioning that saliva is used for these genetic scans, not blood. Then, Dr. Church explained random autosomal DNA recombination, "Each generation you get a scrambling, you get a rearrangement of the DNA...basically there's a half of the DNA from any generation." Dr. Gates then expounds upon what this means for those if us undergoing autosomal DNA testing in the voiceover, "That means you inherit approximately a quarter of your genome from your grandparents [each] and a sixteenth from your great great grandparents [each], so if two people do share a recent ancestor, they will also share long stretches of identical DNA." These matching stretches of DNA are what 23andMe and Family Tree DNA are looking for when they calculate the results for our Relative Finder and Family Finder match lists. When they are able to detect stretches of identical DNA that are sufficient to suggest a recent relationship, these people who match us are reported as predicted cousins. (Autosomal DNA tests can be ordered through 23andMe or Family Tree DNA's Family Finder.)

Dr. George Church founder of The Personal Genome Project

Condoleezza's family had passed down an oral tradition that their paternal ancestress Julia Head was descended from a slave owner named Burrows Woodward Head. Dr. Gates team tracked down Burrows' great granddaughter Rose Mary Head English to perform an autosomal test to compare to Condoleeza's DNA as described above. Geneticist Dr. Joanna Mountain from 23andMe explained, "If they truly are third cousins, we can hope to see some matching DNA, a longer stretch of matching DNA." Once again, as in Dr. Gates case, there was no DNA match. As I mentioned before, for a third cousin relationship, I would recommend additional testing of other family members since about one in ten third cousins will not show a match, but since Condoleezza and Rose Mary are actually second cousins once removed and would be expected to share twice as much DNA on average as compared to 3rd cousins (1.563% versus .781%), it is quite definitive that it was not a match.

Joanna Mountain on "Finding Your Roots with Henry Louis Gates, Jr."

Not content with this negative result, Dr. Gates' team also ordered an admixture test for Condoleeza. This DNA analysis revealed that her genetic makeup is 51% African, 40% European and 9% Native American or Asian. (The tool used for this analysis was 23andMe's Ancestry Painting and is included with their Personal Genome Service.) This proves that although they were unable to determine specifically who Condoleezza's white ancestors were, she definitely has quite a number of them on her family tree.

Next Dr. Gates' team compared the DNA of Ruth Simmons to that of her presumed third cousin Camber Hayman, both descended from the Grapeland, Texas Beasley Family (possibly Charles). Finally, there is a positive match in this episode! Ruth and Camber share 25 cM of DNA across their autosomes (about .33%). This is a predicted 3rd-4th cousin relationship because the amount shared falls between the average amount of DNA expected for a third and fourth cousin (.781% versus .195%). Dr. Gates explains, "The DNA does not tell us the exact generation, but you and Camber share an ancestor since 1800." This is because once the relationship is past second cousins, the random nature of autosomal inheritance makes it difficult to ascertain the exact relationship without more extensive testing of other known relatives.

Ruth Simmons' genetic comparison to Camber Hayman

The truth regarding Samuel's presumed European ancestor, Joel Branham, was presumably too far back for Gates' team to try to sort out using an autosomal DNA test since he was would have been his 3rd great grandfather. The further back an ancestor is in your pedigree, the more difficult it becomes to prove the connection through autosomal DNA testing. It is still possible to do so in the case of a third or fourth great grandfather, but requires extensive testing of extended family on both sides of the equation, an undertaking more fitting for a research project than an hour long television show.

As usual, I wanted the analysis to go further and reach more definitive conclusions. Expert genetic genealogist Dr. Tim Janzen was thinking along those same lines when he wrote to me, "Dr. Gates could have gone another step in his analysis that linked Ruth Simmons to her Beasley ancestor... [he] could have done more autosomal tests on more relatives of Ruth Simmons who were descendants of Mr. Beasley and then compared the data to that of additional relatives of [Camber]. If he had done this...he may have been able to accumulate enough information that he could establish with reasonable certainty which Mr. Beasley was Ruth Simmons' ancestor." Since we saw Ruth's brothers in the episode meeting their cousin Camber, we know that there were at least two other family members whose DNA could have been compared against Camber's. Of course, I realize that trying to fit the family stories of three people into a single episode would not allow for this depth of analysis (but I can dream).

Ruth Simmons meeting her cousin Camber Hayman

For each of the guests, Dr. Gates used the company African Ancestry to recapture some of their deep ancestral information. This company works with Y-Chromosome DNA and mitochondrial DNA (mtDNA) testing, so it can only illuminate the deep ancestry of the guests' direct paternal line (father's father's father, etc...) and their direct maternal line (mother's mother's mother, etc...). This leaves out all of the ancestors in the middle branches of the family tree, but can help trace at least one or two of their "Kunta Kinte ancestors" as Dr. Gates calls them.

Chart of Y-DNA and mtDNA ancestors.
Those ancestors in white are only reached through Autosomal DNA.

Dr. Gates and Dr. Rick Kittles, the scientific director of African Ancestry, did a good job of explaining the process of matching the mtDNA and Y-DNA of "living members of the ethnic groups more highly represented in the transatlantic slave trade" with African Americans today. The theory is that if an African American has a match with one of the African residents in the database, then they share a distant ancestor and can thus deduce the likely origin of their direct paternal or maternal ancestor from what they know of the origins of their African match. Some have argued that these tests are not valid since the tribes in Africa have not stayed static over the centuries and/or the database is not broad enough to ascertain the true genetic origins, but I do not have the expertise to address these objections and would leave it to the reader to do their own research on this subject. (The only issue that I had with the segment was when Dr. Kittles said that the Y-DNA and mtDNA are "identical in every generation". This is not strictly true since they both mutate occasionally.)

Map of the African ethnic groups represented in African Ancestry's database

Since the female guests could only have their mtDNA testing done since they do not possess a Y-Chromosome, their brothers were tested when possible. The results of these tests were compared against the company's extensive database of samples from Africa. Each of the guests were informed which ethnic group their Y-DNA and/or mtDNA matched with the most closely, implying a genetic connection to these areas. Dr. Gates also included the middle school students from the Continuum Project in this exercise. It was exciting to see each of the students excited to connect back to their roots in Africa and hear what it meant to them.

Continuum Project students learning about their African roots

The most surprising result of the night belonged to Ruth Simmons. Her mitochondrial DNA traced back not to Africa, but to the Americas. Apparently, Ruth is the only guest tested in this entire series whose direct maternal line traces back to a Native American. Dr. Gates joked that she was the only African American that he knows whose "great great great great grandmother was a Cherokee Princess." Dr. Tim Janzen suggests that it is more likely that Ruth's maternal line descends from the Caribbean (possibly the Taino or Carib Indian tribes) than from the Cherokee Indians. He opines that this would have been a good time for Dr. Gates to have discussed the origin of much of the Native American admixture in African Americans today. Dr. Janzen explains, "It appears that slaves in the Caribbean were significantly admixed with the native population. Some of those slaves were imported into the US and contributed a significant amount into the African American gene pool." (See here and here for background.) Since Ruth's mtDNA did not reveal an African ancestral line, Dr. Gates tested her brother to learn the deep origin of her direct paternal line. It was indeed of African origin, matching the Kota people of Gabon.

Ruth Simmons' mtDNA's deep origin traces to the Americas

Condoleezza was surprised to learn that her mtDNA traced back to the Tikar people of Cameroon because she said when she visited, the people in Ghana had thought that she looked like she might descend from their Ashanti Tribe. What was not mentioned was that since the mtDNA is only relevant to one of her many ancestral lines, she could well have Ashanti ancestors another ancestral line. Samuel seemed happy to discover that his Y-DNA most closely resembles the Benza people of Gabon. Dr. Gates was clear when he explained that this was an effort to find the origins for just two of the guests' ancestral lines, but to each of them after years of having no information on their African origins, it was obviously a lot.

Condoleezza Rice's mtDNA's deep origin traces to Cameroon

At one point in the episode, Dr. Gates mentioned that "few African Americans have ever been able to discover the facts behind these stories". Although the DNA tests in this episode were not wholly successful in identifying the European ancestors of Dr. Gates and his guests, I am confident that, with time, the technology and the databases will grow to such an extent, that success will be possible for most, if not all, of those searching for their roots.

Next week Dr. Gates will explore the diverse ancestries of Martha Stewart, Margaret Cho and Dr. Sanjay Gupta. Would it be wrong for me to reverse my usual wish and say that I hope that the show uses DNA testing a little less next week? (This took me ALL day!)


I have been writing a review of the DNA testing used in each episode:
Week 1- Episode 1 & Episode 2 - Harry Connick Jr. & Branford Marsalis; Cory A. Booker & John Lewis
Week 2- Episode 3 - Barbara Walters & Geoffrey Canada
Week 3- Episode 4 - Kevin Bacon & Kyra Sedgwick
Week 4- Episode 5 -  Rick Warren, Angela Buchdahl & Yasir Qadhi
Week 5- Episode 6 - Robert Downey, Jr. & Maggie Gyllenhaal