Autosomal DNA: Hints from Our Ancestors

by Finding Your Roots Genetic Genealogy Consultant, CeCe Moore

Autosomal DNA is inherited from all of our ancestral lines, Courtesy: FamilyTreeDNA.com

Autosomal DNA is inherited from all of our ancestral lines, Courtesy: FamilyTreeDNA.com

Last week’s episode featuring Derek Jeter, Billie Jean King and Rebecca Lobo concluded with a short vignette about each of their DNA. Cumulatively this 6-minute piece represented many hours of research and necessarily simplified the process that led us to the conclusions presented. As promised, I will share details of some of the genetic genealogy work done behind the scenes.

Autosomal DNA is inherited from all of our great grandparents and they inherited it from their great grandparents, so we are made up of little bits of our ancestors. Those most closely related to us have contributed the largest fragments of DNA to our genomes, while the more distant ancestors have contributed smaller ones, if any at all.

When I first reviewed Derek Jeter’s autosomal DNA results, even before the research team had begun working on his genealogy, something immediately caught my eye. A number of his matches – those sharing long stretches of DNA with him – had Jeter ancestors of European descent in their family trees. I couldn’t help but be intrigued so I jumped in and started researching his Jeter ancestral line. This eventually led to his 2nd great grandfather Green Jeter, Green’s slave owner James W. Jeter and the question regarding the nature of the relationship between the two. The matches that I had initially noticed, Derek’s 59.4% European ancestry and the clues turned up through the paper trail genealogy research, inspired me to use DNA to try to determine if they could have been father and son.

DNA testing additional family members is often essential to my research. As I mentioned in my first article, I always seek to test family members of the guests as well as any descendants of theorized ancestors. For the Jeter research, we were fortunate that a number of crucial people, including Derek’s father, agreed to be DNA tested. We were also able to find key matches in the already existing databases. We utilized both Y-DNA and autosomal DNA testing in our attempt to determine whether James W. Jeter is Derek’s 3rd great grandfather.

Since Derek does not descend in a direct paternal line from Green Jeter, but rather through his paternal grandmother Lugenia, we were unable to use his Y-chromosome for testing the theory that Green was the son of his slave owner. That didn’t mean that we were out of luck however. We followed the direct male descendants of Green Jeter down to the present day – from father to son – and asked one of Derek’s cousins to take a Y-DNA test. Fortunately, he agreed. To ensure that this cousin did indeed share a genetic relationship with Derek, we tested his autosomal DNA as well. Next, we needed a direct male descendant of James W. Jeter. To find one we built James’ family tree forward in time, a process called “descendancy research”. When we located his 2nd great grandson he generously agreed to test as well. Both the Y-DNA matches and the autosomal DNA matches supported a familial relationship between Green Jeter and his master James W. Jeter. When the DNA evidence was examined in conjunction with the findings from the slave schedules, wills, tax records and land records it made for a solid case that James W. Jeter was indeed the father of Green.

A visual breakdown of Derek Jeter's admixture prepared by the Finding Your Roots team.

A visual breakdown of Derek Jeter’s admixture prepared by the Finding Your Roots team.

Rebecca Lobo had an intriguing and unexpected result from her autosomal DNA test as well. Since autosomal DNA is inherited from all of our great grandparents, it offers insight into each of their ancestral origins. Rebecca’s results revealed a substantial amount of Jewish ancestry, about 10.2%, which falls within the range of what one inherits from a single great grandparent (12.5% on average). Since she has an unknown great grandfather, this was exciting. By testing additional family members and examining the placement and size of the Jewish DNA segments, we were able to reach a definitive conclusion. The pattern across Rebecca’s father’s chromosomes revealed that his Ashkenazi Jewish DNA (21.8% of the total) was inherited from his parent with Eastern European ancestry and not from his parent with Southern European ancestry. Therefore, we were able to state with certainty that this ancestry originated from Rebecca’s paternal grandmother’s branch of the tree. Although we were unable to determine the identity of Rebecca’s unknown great grandfather, her Jewish ancestry is a tantalizing clue.

Lastly, through exploring Billie Jean King’s autosomal DNA we were able to address her family’s oral history and answer the question of whether she had recent genetic Native American ancestry. Since we inherit autosomal DNA from all of our 2nd great grandparents (and almost always all of our 3rd great grandparents too), the breakdown of our ancestral origins, also known as admixture, will be representative of the DNA passed down to us from them. Billie’s admixture revealed no traces of Native American DNA whatsoever. That isn’t to say that she didn’t have a more distant ancestor of Native American ancestry or a recent ancestor who was culturally and socially Native American, but we can conclude unequivocally that she does not have a recent ancestor of substantial Native American genetic ancestry.

Contrary to my expectations, in episode three you will see that autosomal DNA helped to prove one of the guest’s oral family history. In my next article, I will share the surprising journey of that discovery.