23andMe DNA kits are on sale through October 15, 2019.
Clustering methods are all the rage in genetic genealogy these days, for good reason. They offer a tidy visualization of which of our DNA matches also share DNA with one another. That’s information we can use to corroborate our biological family trees and to identify brick-wall ancestors. What clusters don’t do, however, is generate a family tree for you.
23andMe just changed all that!
A few days ago, 23andMe surprised us all with a new “auto-built” tree feature based on shared DNA clusters. The tool, simply called Family Tree, is currently available to customers who have signed up for 23andMe’s beta testing program. It’s accessed via the Family & Friends menu. (You can sign up, too, using the instructions at the bottom of this post.)
The tree generated for my father looks like this. I’ve replaced the match names with letters to protect their privacy. These matches all share 50 cM or more with my father.
What’s going on here?
23andMe’s FAQ says:
When you participate in DNA Relatives or make one-to-one connections with other 23andMe customers, 23andMe compares your DNA and predicts your genetic relationships.
To build your predicted family tree, we then go a step farther: we also look at the relationships between your relatives, and calculate many different ways you could all be related to each other. The tree you see represents the most likely tree out of all the possibilities we calculated.
Without explicitly stating so, 23andMe has clustered the 15 matches who share the most DNA with my father (including myself) and fit them into a hypothetical tree based on whom else they match, how much DNA they share with us and with one another, and their ages.
To see what I mean, compare the family tree above with this cluster report from the DNAgedcom Client for the same set of matches. Matches are listed in order across the top and down the left side. Where two matches also match one another, the intersecting box is colored in. The cells on the diagonal are always filled in, because that’s where each match is compared to themselves.
Match G is a first cousin once removed to my father. Match G also shares DNA with Matches A through F and with Match H, but Match H doesn’t share DNA with any of the others. 23andMe’s system has figured out that Match H is related through one branch of the tree while Matches A through F are related through another.
What’s more, the algorithm is comparing how much each pair shares to estimate how they are related to one another. For example, Match C is the father of Match D, so 23andMe put them as parent–child in the tree. That one’s easy, of course.
A more sophisticated analysis suggests how Matches A, B, and C might be related to one another. Match C shares approximately 800 cM with both Match A and Match B, which is in the first cousin range. However, Matches A and B only share about 200 cM with one another, so the three of them can’t all be first cousins to one another. An alternate scenario is that Matches A and B are 2nd cousins to one another and Match C is their great uncle. This possibility fits better to both the DNA data and to their ages (which we users can’t always see but 23andMe’s system can).
And that’s precisely what turned out to be the case based on a quick dive into their family trees. I already knew how Match C was related to me, and it only took a few minutes of online research to corroborate that Matches A and B are the grandchildren of his brothers.
You Can Annotate the Tree
An exciting feature is that you can annotate the tree with the names, birth/death years, and locations of the people in the tree. Eventually, the deceased people in your tree will be visible to your matches, much like at 23andMe’s competitors, enhancing your genealogical research and that of your matches.
Tree annotations are still in development, and there are limitations. For example, Maria Eva Weigel in the screenshot above was married twice. Her daughter Elizabeth Mühl was the only child of her first marriage, so the descendants of her second husband (Jacob Schmitt) are half cousins to us. There is currently no way to indicate half relationships in the system.
Nor is there a way to correct placements that turn out to be wrong. All of the matches in my father’s auto-tree were on the correct branches, but several were in the wrong generation (see below). Other users are reporting that maternal relatives are linked to the paternal side and vice versa. 23andMe plans to introduce a tree editor to allow us to correct these issues, but it’s not available yet. (That’s the down side of participating in a beta program.)
Key to remember is that the tree isn’t “sided”, meaning that you can’t tell whether your matches are maternally or paternally related to you by which side of the diagram they’re on. For example, in my auto-tree, my paternal matches are on the left, while in my father’s tree, his paternal matches are on the right.
Also, the system doesn’t appear to be using haplogroups or X segments to “side” people. My father shares a substantial amount of DNA with Match D on the X chromosome, which men only inherit from their mothers, but 23andMe gave no indication that Match D is a maternal match. Perhaps they will use X DNA and haplogroups to “side” our trees in the future.
Finally, bear in mind that the proposed relationships are educated guesses, not fact. Of 13 matches in my father’s tree (excluding myself and the child of Match C), I’ve been able to place 10 of them definitively. All of them are positioned on the correct branches in the auto-tree, but five of them are in the wrong generation. Four of those five are estimated to be one generation more distantly related than they really are, e.g., a 2nd cousin once removed said to be a third, while one is a true third cousin said to be a 2nd cousin twice removed. I expect the estimates to improve over time as they gather more information from real-world relationships and as the database grows.
Oh, and the font size … oh my! The tool was clearly programmed by someone who has 20-something year old eyes, whereas mine are a few decades older. The names are so small they’re almost impossible to read. That’s what customer feedback is for, right?!
Sign Up for the Beta Program
Enrolling in the beta program gives you access to new features early. Companies beta test newly developed products to see how customers respond. For that reason, you should understand that beta tools may have unexpected glitches and are likely to change over time as the company continues to perfect them. If you’re not comfortable with that, wait for the finished product rather than joining the beta program.
If you’d like to go ahead and join, here’s how:
- Log into your 23andMe account and click on your name at the top-right to get a pull-down menu. Click “Settings”.
- On the next page, scroll down to the “Preferences” section and click the hot pink “Become a tester” button.
- That’s it! You should be enrolled in the Family Tree beta program within a day or so.
- The tree is accessed via the Family and Friends menu in your 23andMe account.
- The system may walk you through a couple of introductory screens before you can see the tree. These are expected to change as 23andMe develops the system.