You didn’t get all of your ancestors’ DNA, but your close relatives inherited some of the DNA that you didn’t inherit.
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: