AncestryDNA’s updated DNA Matches (now in beta testing; available here) has a nice little surprise for those of us who take a statistical approach to our DNA work.
Click on the shared DNA amounts in your match list.
Alternately, you may have a little “i” in a grey circle beneath the predicted relationship. Click it.
You’ll get a pop-up window with some interesting information.
The example above is my mom’s first cousin. She and I share less than average for first cousins once removed; only 32% of people who share 293 cM are 1C1Rs; the majority (63%) are second cousins.
The most likely relationship isn’t always the relationship. An essential question in DNA-based predictions is ‘How much more likely is one relationship than another?‘
Previously, the best data we had for that came from simulated data in Figure 5.2 of the AncestryDNA Matching White Paper, and it took some doing to get the numbers into a useable form. The probabilities from Figure 5.2 are integral to the Shared cM Project Tool and What Are the Odds? at DNApainter.com.
The numbers in the new DNA Matches feature at AncestryDNA are different from the previous data, and they also go down to lower centimorgan levels. I suspect that Ancestry’s scientists have redone their simulations now that their database is larger and improved the likelihoods. This is good news! Better probabilities will improve the predictions in tools like What Are the Odds?
Would you like to help? Compiling this new data from match lists is perfectly suited to crowd-sourcing. The values for centimorgan amounts below 280 cM have already been compiled. You can contribute percentages for matches above 280 cM by completing this survey.
If warranted, the new probabilities will be used to improve the relationship prediction tools at DNApainter.com.