Tuesday, April 19, 2016

Update: Expect changes in your AncestryDNA results in next week or two.

As I mentioned in my previous post, changes are going to be made in Ancestry's Timber algorithm in the next week or two according to Blaine Bettinger in a post on his Genetic Genealogist blog.

Update: Action post from Roberta at DNAeXplained regarding this change. https://dna-explained.com/2016/04/19/upcoming-ancestry-dna-update-urgent/

I won't quote all of Blaine's post here, you can read it for yourself at
http://thegeneticgenealogist.com/2016/04/19/ancestrydna-plans-update-to-matching-algorithm/, but here are some significant changes mentioned by him in his post.

Among the changes that are expected in this update are the following (bolding below is mine):
"•Phasing Improvement – AncestryDNA has significantly increased the reference haplotype set used for phasing prior to cousin matching, meaning that the quality of AncestryDNA’s phasing will increase. This should result in fewer phasing errors, and thus fewer lost matches and false positives."
"•Matching Improvement – AncestryDNA is changing how they identify matches between individuals. Previously, AncestryDNA was using “windows” or blocks of DNA to compare two individuals. They will now be used a SNP-based method to compare people. The problem with the previous method is that if the windows didn’t overlap a segment properly, they could either miss the segment entirely or shorten the segment. The SNP-based method will no longer miss or shorten these segments. As a result of this switch, it is expected that many matching segments will increase in size. The total shared cM with many, and possibly most, matches will increase."

"•Match Confidence Changes – there will also be a change to the matching thresholds/confidence scores; specifically, the relationship prediction thresholds will be more stringent. As a result, we will see some of our existing matches SHIFT; they will NOT be disappearing. Thus, we will NOT be losing any 2nd, 3rd, or 4th cousin matches, in the sense that these matches are gone. Instead, we will see some 2nds go to 3rd or 4th (possibly, but this will be a rare shift for most existing customers), see some 3rds go to 4th or distant (slightly less rare), and we will definitely see many 4ths go to the distant category."

Bottom line for me, at least, is that I will have to go back to every match entry in my database and update them all with the new information. I would suggest that you all record your current total page count for each of your test an then when the change is made, you will have a better understanding of when the change has been made and the impact on your total matches. Depending on your preference you may wish to hold off recording info in your spread sheets until after the latest changes are made. I will get a real good look at what changes are made thanks to all the info in my spreadsheet already.

So I am batting a thousand. Teach Ancestry in genealogy one of my genealogy classes and expect major changes after class is over.  Guess that keeps me in business. ;-)