The AncestryDNA blog features a cute story in which two coworkers test at AncestryDNA and discover that they share matching DNA. This leads to the discovery of shared ancestry:
After a little research together, the connection was discovered. They share 3rd great grandparents. Stephanie shared a picture of the common ancestors they likely inherited their shared DNA from.
AncestryDNA too often creates the impression that if two people share DNA and identify common ancestry in their respective family trees — *presto* — they’ve discovered the likely source of their shared DNA!
Unfortunately, genetic genealogy is rarely so easy.
A number of genetic genealogists have pointed out the errors of AncestryDNA’s ways.
"Ancestry does a good job of linking up people who match by connecting people in their trees. But that doesn’t mean that connection is how they are genetically related…"
"If we are from the same geography, it’s likely that we match on multiple lines. What if we match on paper on two or three lines? How do we know how we are genetically related – through which line or lines?
"At Ancestry, you don’t – you can’t – because they want to ‘keep things simple.’ Let me translate – they would rather leave you with a vague ‘feel good’ notion about who you are related to, even if it’s not true, than give you the tools to discover the truth."
"So, out of my ten matches that have shaky leaves attached, three of them apparently have common ancestors wrongly identified as the source of our matching DNA. Do you see the problem here? Does AncestryDNA? If this match were, instead, at 23andMe or Family Tree DNA, I could check the DNA segment that we share and compare it to my other matches and/or my chromosome map. This would provide additional information and/or evidence to help me determine through which of my ancestral lines this segment of DNA was inherited."
"Without a chromosome browser and access to shared DNA segment data, customers of Ancestry.com’s autosomal DNA genealogy product, AncestryDNA, cannot positively identify the ancestors responsible for the DNA shared with each genetic relative. Without access to and analytic tools for shared DNA segment data, AncestryDNA customers routinely draw inaccurate conclusions about their pedigrees and how they relate to each of their reported DNA matches."
"Customers of genealogical DNA testing from other companies have been asking for better DNA analysis tools. Ancestry.com refuses to supply them, their rationale being concerns of ‘privacy,’ and the idea that they want their product to be more ‘simple’" …
"Simplicity does NOT mean that you deliver an inferior product, on purpose, at full market price to customers who don’t know any better. That is not true simplicity. It’s dishonesty."
Fortunately, there are some third party resources that provide the essential tools that AncestryDNA lacks. (E.g., GEDmatch.com)
Unortunately, it seems as if AncestryDNA doesn’t want people to talk about those resources.
Earlier today, I made a comment on the blog post about the coworkers who found out that they were distant cousins:
"…the common ancestors they likely inherited their shared DNA from."
They need to triangulate to be sure. That requires a bit more luck and a lot more work. For best results, transfer you DNA raw data to GED-match.
On my first attempt to submit the comment, I was immediately slapped down by the spam filter. From prior experiences with Ancestry, I suspected that the word “GEDmatch” was the problem. So I put a hyphen in. ”GED-match” made it around the filter. But a few hours later, I found that my comment had been deleted.
I’ve submitted the comment again (3:51 AM Eastern Time, 25 July 2014). We’ll see how long it holds up:
CeCe Moore provides an update on Ancestry DNA:
In response to questions about AncestryDNA’s plans for adding a chromosome browser or segment data, Kenny repeated that Ancestry is working on something that would give their customers access to that type of data, but that it would be something different than what current chromosome browsers offer. No date was provided for launch or when such a feature might appear. He did admit that at this point the tools that Ancestry has for triangulating data are quite lacking…
In a somewhat related slide, Kenny showed several of his lines that had been “confirmed” by DNA shaky leaf hints. He said that this was “independent” evidence that his tree was correct. As readers of this blog know, unfortunately you cannot always say that is the case.
Some comments related to this important report…
I am amazed by how poorly understood genetic genealogy is, even among those who have a vested interest in understanding it. I’m afraid that very few understand the importance of triangulation and many are misled by AncestryDNA’s shaky leaves. A couple of simple diagrams could make this very clear.
This problem would also become clear for more Ancestry customers if they could see that they have matches who share two ancestral lines but share only one DNA segment. Maybe releasing customers’ matching segment data would burst a few bubbles, but the truth needs to come out or this is going to become pseudoscience for a lot of people.
On the issue of centimorgans at AncestryDNA, I’m happy to hear they’ve made the necessary change, but I’m confused:
"If you tested recently, then your matches are in centimorgans. If it was prior to that date, then your matches are in megabases."
As someone who tested before the switch, does this mean that my matches are stuck in megabases in perpetuity, or does this mean that my older matches are measured in megabases and my newer ones are measured in centimorgans?
Going forward, I hope Ancestry can see the necessity of opening matching segment data, at least for those who would be inclined to opt in. At some point, AncestryDNA could become a bit tarnished when people begin to learn that the shaky leaf hints are unconfirmed possibilities that could be dead wrong.
I hope that anyone who is planning to order mitochondrial testing knows a bit more about it than I did when I sent for my test.
If you’ve decided to do mitochondrial testing, more power to you. The whole community of genealogists will benefit as the database grows. But be aware of the limitations of mitochondrial DNA and adjust your expectations accordingly.
If you scour the internet looking for mitochondrial DNA success stories, you probably will have a bit of difficulty. Why?
Here’s why: In contrast to autosomal DNA and higher level YDNA testing, mitochondrial DNA testing tells you very little about your ancestral connections within the “genealogical time frame” (≈ 500 years). According to Family Tree DNA, full sequence mitochondrial matches reach a 95% confidence interval only when you go back 22 generations. Going back 5 generations, the confidence interval is only 50%:
This doesn’t mean that you can’t put mitochondrial DNA to good use, but it does mean that you will not be able to use it the way you use Y DNA or autosomal DNA. Mitochondrial DNA is generally not a good test to confirm connections or to find matches who are related through a common ancestor within the past 5 or 10 generations.
The primary genealogical value of your mitochondrial testing results is in excluding people from your direct maternal line. In other words, if you need to rule out a specific hypothesis relating to your direct maternal line, mitochondrial testing might be just what you need.
On the other hand, don’t forget that you can learn quite a bit about your direct maternal line (and all other lines) with autosomal testing. In my case, I’ve learned much more about my direct maternal ancestry from autosomal testing than I ever expect to learn from mitochondrial results.
As for me and my family, we’ll earmark our DNA testing funds for autosomal testing (and maybe some targeted Y DNA testing) until we run out of people to test. After that, maybe we’ll give mitochondrial DNA another look.