No matter how expert you think you are, there is always something to be learned from others.
When I saw that Michelle Trostler of DNA Detectives on Facebook and Identify Family was giving a talk on getting started with AncestryDNA for my local DNA special interest group, the North San Diego County Genealogical Society, I knew I should go, and I am glad that I did.
Personally, I use the Ancestry.com DNA testing service the least of the big three because all my ancestors are relatively recent arrivals (late 1800s and 1930s) so I do not have as many DNA matches there as elsewhere. Thus I know far less about using that site than the others.
Michelle is a knowledgeable and confident speaker. You can hear her at the upcoming i4GG seminar in San Diego as well.
Here are some of the tips from her talk that I found particularly useful.
Many people have the illusion that if their testing company says a person is a 3rd to 5th cousin they really will be. That is not the case.
The testing companies are just making the best guess they can from the data they have. They do not seem to take segment sizes into account, rather they primarily use total shared DNA measured in centimorgans (cMs) for their relatedness estimates, usually the sum of all matching segments of 5 cM or larger. Close relatives will always share larger chunks with each other and so size does matter here.
Recently I have received numerous questions from people trying to figure out if a new match is a half sibling or a niece or a grandchild. These are hard to tell apart without testing more relatives as they all share about 25% of their DNA with each other. So I decided to collect some detailed statistics on those specific relationships with a google form (click here) that includes total segments and segment sizes for a future blog post.
The companies predict reasonably well for close family but it is just not possible to be accurate beyond that due to the randomness of DNA inheritance.
For example, here is a picture from the new 23andme of some of the DNA I share with Dick, a 2nd cousin on Dad’s paternal side so blue, and John, a 2nd cousin on Dad’s maternal side so red.
I share a third again as much DNA with John as I do with Dick, even excluding the 14 cM on the X. The expected amount for a 2nd cousin is 3.125% which is 212.50 cM, right in the middle between these two.
Checking my brother, I see the same effect – he has 282 cM with John versus 185 with Dick. Not surprisingly, when I look at Dad I find that he shares almost twice as much with John as with Dick. Clearly he just inherited more of the same DNA as John’s mother from their common grandparents. Conversely, he inherited less DNA shared with Dick’s mother from his other grandparents.
On the left is a comparison of my first cousin Henry with both Dick and John. The amount he shares with each 2nd cousin is practically identical, as long as you subtract the 40 cM that he shares with John on the X from the total shown by 23andme. Amazing how variable DNA inheritance can be among 2nd cousins.
Click here for the ISOGG wiki article on Autosomal DNA statistics which usually includes the current chart from Blaine Bettinger’s shared centimorgan DNA project.
It is so delightful that you can now easily view your past correspondence with a 23andme match! To do this go to DNA relatives, which defaults to the People section, and click on the person. This takes you to a one-to-one comparison page partially shown below.
Your most recent message will appear in a box in the right hand column and you can scroll back in that box to see previous messages, both sent and received. Not all my oldest messages are there and I am not sure why. I did find one from 2012 and all the ones since 2014 seem to be available.
Past correspondence in the People view – as always, the red arrow has been added by me
I used to have to use the chrome add-on 23++ in order to search my inbox or outbox which took a long time with four years worth of messages to search. Sometimes it even crashed! This is much better.
More on the People view in DNA Relatives
Can’t find the person? You can use the search box on the right in the People view to find them, an improvement over the first roll-out of the new site. Note that the search in the DNA view works immediately as you type, no buttons to push, while the search in this People view requires you to press return. Annoying that they are different.
You can now download your aggregated results from the bottom of the People view page. Continue reading
Many months ago we were promised that the transition would come in August. Last week on July 15, several of my accounts got an email that it was coming in a few days. Today, twelve days later, two of the ten or so accounts I manage at 23andme got emails that they have actually transitioned to the new experience, mine and my dad’s.
This is particularly exciting for me as I can now try out the new automated triangulation tool (click for previous blog post on that) with Dad and my Norwegian 3rd cousin. You need to participate in open sharing to have access to this tool.
When I visited Norway last summer, kits in hand, my third cousin gave me his DNA, so of course he got the new 23andme. I did a blog post on the new experience with his kit and went into the details of how to do the things I was used to doing on the old site on the new site – comparing people, asking for shares, checking new relatives, and so on. In this post, I will try not to repeat myself but rather to report on how the transition worked for me.
If your kit has transitioned, when you log in you see a big green button that says Get started that you have to click, as in the image above.. Continue reading
Matching DNA has put me in touch with an extremely large number of Norwegian cousins who share my fifth grandparents from Fatland farm on Halsnøy Island in Hordaland, Norway. What’s more, perhaps due to the large number of them, I am seeing some triangulation of segments among their results.
Halsnøy Island in Hordaland, Norway from the ferry
This started me thinking about the effect of many generations of big family sizes on the number of sixth cousins I might have from a specific set of 5th grandparents. It would seem to me that the larger the number of cousins, the more likely it is that there are some who share good sized segments with me and Dad.
So I did a little simulation in a spreadsheet. It’s very simple, it assumes that the number of children reproducing in every generation is the same so that you can see the differences for different family sizes. I also did a line or two with the real/estimated numbers from the Fatland couple.
If your family consistently had two children who had two children reproducing for six generations you would only have 64 fifth cousins, but if everyone in your family had six children who had six children then you have almost 50,000 fifth cousins. Quite a difference!