Published April 10, 2017

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A couple of weeks ago, your “Roots & Branches” columnist tackled the explosion of DNA testing in genealogy with the caveat that I know “only enough about DNA and genealogy to be very dangerous.”

You can continue to attach that caveat to anything I write about DNA, but I feel compelled to write about it again with the formal rollout of AncestryDNA’s “Genetic Communities” tool.

First, a comment on what this tool is not. Many folks taking genealogy DNA tests have been most fascinated by the “ethnicity estimates” that Ancestry and other companies have offered.

For these ethnicity estimates, test takers are matched against others in a database and shown rough percentages of “Western European” or “sub-Saharan African” or other such ethnicities at a deep-ancestry level … hundreds or thousands of years ago.

Savvy amateur and professional genealogists tend to roll our eyes at this ethnicity stuff and politely term it “good cocktail party talk.”

The ethnicity estimates, in my opinion, don’t mean much because – especially with such a long lag in time – migrations and misreporting of ethnicity in the database you’re being matched against can result in information that’s easy to misinterpret.

The “Genetic Communities” tool, on the other hand, starts with its target more recent ancestry, particularly the century of 1750 to 1850. The science requires a little more information than a column this length can handle, but Ancestry has an explanatory “white paper” and other question-and-answer primers available at this URL,

For casual genealogists without particularly well-developed trees, the “Genetic Communities” tool has the potential to immediately expand their universe of ethnic and geographic possibilities.

For more experienced genealogists, the tool may only reinforce the paper research that they’ve already done. But it’s probable that some will find a “Genetic Communities” assignment that’s completely new to them, especially if they have a line that they haven’t been able to get back very far (which often bears a decent chance of having been from a different ethnicity – making that line more difficult to trace).

The tool goes beyond DNA to link the samples up with reported migration patterns of the ancestries included in the database. AncestryDNA used literally millions of samples – which includes billions of DNA data points – to build the “Genetic Communities” networks.

While not every individual is assigned to a “Genetic Community” – it depends on how widely dispersed their ancestral DNA is – others are assigned more than one.

As exciting as this tool is now – it will grow only bigger and better as more Ancestry customers test and more “Genetic Communities” are identified.

In addition to Ancestry’s own materials, Blaine T. Bettinger, author of “The Genetic Genealogist” blog, has a great post on the tool … including a downloadable handout listing all of the 300 or so “Genetic Communities” identified so far by Ancestry.