Friday, August 8, 2014

AncestryDNA – #BYUFHGC

Michelle ErcanbrackYou’ll have to give me a break. AncestryDNA was the final topic addressed by Ancestry.com family historian, Michelle Ercanbrack. She presented it in the last session on the last day of the BYU Conference on Family History and Genealogy. By this time, my note taking was crumbling into discombobulation. I’ll have to supplement my notes with Ercanbrack’s excellent syllabus.

The contents of the AncestryDNA homepage depend on whether or not you’ve purchased a kit. If you’ve not yet purchase one, the page makes a sales pitch, answers questions, and guides you through the process of purchasing a kit. Four to six weeks after submitting your kit, your DNA home page changes.

The AncestryDNA home page makes a sales pitch if you've not purchased a test 
AncestryDNA home page before purchasing a kit

 The AncestryDNA home page shows your test results if you've purchased a test
AncestryDNA home page after receiving your results

AncestryDNA is an autosomal DNA test. This gives rise to two distinct sections of your DNA test results: ethnicity estimates and cousin matches. Click on either big green button to go to that part of the test results.

Ercanbrack made an important point about the ethnicity estimate. “This is not a pie chart of my pedigree, it is a pie chart of only what I have inherited.” [Earlier in the conference, presenter Angie Bush showed a wonderful chart from Blaine Bettinger’s The Genetic Genealogist blog. The article “Q&A: Everyone Has Two Family Trees – A Genealogical Tree and a Genetic Tree” from 10 November 2009 includes a graphic illustrating the concept that not all your ancestors are represented in your DNA. The shaded ancestors in Bettinger’s fan chart are those whose DNA markers survived to be detected by a DNA test.]

Your Genetic pedigree is a subset of your genealogical pedigree.
Credit: Blaine Bettinger, The Genetic Genealogist

Let me repeat what Ercanbrack said. “This is not a pie chart of my pedigree, it is a pie chart of only what I have inherited.” There is a literal pie chart, but Ancestry.com has deemphasized it. If you look carefully, you can see that the colors in the pie chart, on the map, and in the legend all match.

AncestryDNA compares your DNA to a reference panel of 4,245 DNA samples of natives scattered across 26 regions around the world. This gives, within certain error bands, your distant, ethnic ancestry.

My results are pretty boring. I’m mostly British. My single Scandinavian line looks overrepresented, but that can have several explanations. As ancestors dropped out of my genetic family tree, my Scandinavian ancestors may have been spared in above average amounts. Or Scandinavian incursions (translate: Viking pillaging) into England may have left their mark (well, markers, actually).

AncestryDNA ethnicity estimate report

Likewise, my Irish ancestry seems overstated. But I can click on the name of the region to do a deeper dive. Doing so shows that the stated 21% Irish ancestry might actually be in the range of 6% to 36%. It also shows other information about the region and the reference panel. There are 154 people in the Ireland reference panel. [It occurs to me that Ancestry’s choice of reference persons can also skew results.]

Cousin Matches is the other major section of the AncestryDNA website. It lists other people who have taken the AncestryDNA test who share a significant amount of DNA with you. [AncestryDNA lists 11,500 matches for me, ranging from an uncle to 8th cousins.

AncestryDNA cousin match list

For each match, AncestryDNA specifies a possible relationship and a confidence level for that relationship. If the possible relative has submitted a tree, it shows the number of persons in their tree. If AncestryDNA can find a common ancestor, it displays a shaky leaf next to the person count. When a common ancestor is found, you can display a chart showing exactly how you are related. It also shows when the possible relative last logged in, which sets your expectation as to whether or not the person would respond if you tried to contact them.

AncestryDNA cousin match

While AncestryDNA displays possible matches out to 8th cousins, they warn that 5th cousins or more distant have a less than 50% chance of actually being that closely related. AncestryDNA identifies one of my 8th cousins and was able to find a common ancestor. Our common ancestor was a Dutch settler in New Amsterdam.

AncestryDNA relationship chart

AncestryDNA displays surnames common to your tree and theirs and displays the match’s pedigree, which is helpful when no common ancestor is identified.

In closing, Ercanbrack shared the New York Times article (“Stories That Bind Us,”) about the Emory University study showing that teenagers who know their family histories are more likely to show a higher levels of social and emotional health. She told us that after 9/11, a follow-up story confirmed these results. She challenged us to “find your why” for doing your family history.

2 comments:

  1. This is such an important point about DNA and purported ethnicity: You do not inherit equally from all of your ancestors, so the "results" reflect only what you inherited and do not represent all of your ancestry.

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  2. It is critically important to understand that without chromosome matching tools, these matches mean NOTHING. The shaky leaves merely tell you that you share a common ancestor - NOT which common ancestor has given you the shared DNA. Without going to third party tools, you are fooling yourselves if you think these so-called matches can break down a brick wall. Maybe all those apparent common ancestors mean a breakthrough and maybe all your possible cousins just copied the same misinformation into their trees. And most of you are part of the 50% that don't match at all.

    Beg, demand, cajole... Ancestry into providing real, worthwhile tools instead of prettier graphics.

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