• DNA
  • Dec2

    4 Comments

    UPDATE February 2, 2016: Now that it is more than 2 years down the road, I’ve taken some time to spice up the chart’s flavor a bit and added a 4th-great-grandparents column, as well as the average shared centimorgans (cM). Average cM is very useful when comparing match data from 23andme’s Relative Finder, for example.

    I also added a link right on the chart that will lead people to the Autosomal DNA Statistics over at ISOGG (also linked below in the original post.)

    The chart is still licensed under Creative Commons under the Attribution-ShareAlike license, but I added the Non-Commercial option to it. I’m all for sharing with the community, but if a business wants to use it I’d like to have some say. (Of course, if you are an independent genealogist looking to use it in your work for clients, I may be enticed to limit my charge for its use to a cup of coffee or a firm handshake.)

    Read on for the original blog post – if you dare!…

    Can you say consanguinity? Sure you can.

    If unfamiliar with the term, or kind of familiar as I was before I dove headfirst into this whole genealogy world, The Wikipedia nicely defines it this way:

    Consanguinity (“blood relation”, comes from the Latin consanguinitas) refers to the property of being from the same kinship as another person.

    As one gets going with genealogy, the first real hurdle we need to get past is the whole “What is this ‘eleventeenth cousin thrice removed’ stuff all about?” So, being mostly a visual sort of learner I created a chart to help myself get the idea straight.

    Over time I’ve moved on from needing to reference that chart too often, but lately I’ve found I needed a new addition to that cheat sheet – Shared DNA percentages.

    Why on earth would one need such a thing? If you’ve had your autosomal DNA tested at 23andme or FTDNA, then you are probably getting hints for new cousins all the time. When the familial connection is not obvious (as it almost always is not), it is a good to know how much DNA one might share with a, say, 4th cousin, so you can start looking in the right part of the old family tree for them.

    Consanguinity Chart Now With More DNA Flavor!

    To give me the visual my brain needs to absorb the info, I created this chart at right. If you’d like a copy for your very own, feel free to click this link and download a full size copy from my Box.com account.

    However, shared DNA is not an exact measure of “relatedness” as it falls in the traditional family tree. Due to the random magic of recombination, there is actually a range for how much DNA actually gets passed on from one’s ancestors. For example, while on average one inherits about 50% of each parent’s DNA, the actual amount can be somewhat greater or lesser. As you can imagine – apply that inheritance wiggle room to a 4 or 5 generations between yourself and your match on 23andme and the number can vary quite a bit.

    (I suggest reading ISOGG’s Autosomal DNA Statistics page for a nice overview of this whole topic.)

    In fact, a recent relatively close match of mine on 23andme illustrates this point nicely – I had a new match show up in my results as a possible 4th cousin, among my highest. Nicely for me, this cousin was on my mother’s side, and she has been tested as well.

    23andme Cousin Match Comparison
    Using my handy-dandy consanguinity chart, at 0.27% shared DNA over 3 segments, one can see the result is a bit above the 4th cousin level. All righty! But, if you look at what my mother shares with this same cousin you’ll notice a disparity in the estimate – they share 1.04% over 6 segments. The other good news in this particular match was that she had an obvious surname and location in her profile that I knew about – and is the first person I have been able to find that I can tie directly into my known genealogical research.

    Her actual connection to my mother is as a 2nd cousin, once removed, and a plain vanilla 3rd cousin to me.

    As such, I should expect to share about 0.781% DNA with her – but because I did not happen to inherit 3 of the segments my my mother shares with her, we only have a third of that amount in common.

    Without access to my mother’s results in addition to my own and without the ability to connect to established paper-based research, I easily could have started barking up the wrong tree – and at the 4th or 5th cousin level there are a lot of trees.

    So, while I still think the chart is a nice reference to have as a starting point in the process, those shared DNA percentages need to be taken with a grain of deoxyribonucleic acid. or maybe some sodium chloride.

    Hope people find the chart useful – I have posted it under a Creative Commons license as listed below.

    Creative Commons License
    Consanguinity Chart Now with More DNA Flavor! by John J. Tierney is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.
    Based on a work at http://currach.johnjtierney.com.

  • Feb20

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    My 23andme Ancestry Composition Chart

    Click image for larger version.

    23andme recently released a new Ancestry Composition tool that “tells you what percentage of your DNA comes from each of 22 populations worldwide.”

    It is a nicely designed chart – although according to discussion on their forums and even my own results, the specificity seems to affected by the current size of the comparison data set.

    My ancestry is 50% Irish and 50% Czech and I can name the exact towns where 6 out of 8 of my great-grandparents came from. My 99.6% reported European ancestry is purported to be in the “sweet spot” of their data – however my results have a fair amount of “Nonspecific” percentages. They also show what I think is probably noise in their analysis with tiny amounts of South Asian, Middle Eastern and North African in there as well.

    With 23andme’s big push to reach a database of a million people, it will be interesting to see how this composition chart changes over time – assuming they update it regularly as new information becomes available. (Some other reference info on the site has not seemed to keep up with the times.)

    Overall, I am quite happy with the service and hopefully I’ll find a match one day that will help me find where them long lost Tierneys came from back in Ireland.

  • Jan28

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    This method was successful. Your outcomes may vary.


    Dearest Mother

  • May10

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    UPDATE (09 NOV 2015): 23andme is retiring Countries of Ancestry (the tool formerly known as Ancestry Finder) as of November 11, 2015. I’m leaving this blog post out here for posterity, mainly due to vanity and the amount of time I put into creating my Excel sheet. 😉

    Update: I have made some changes to the Import tool – you can download the latest version at the original link listed below. See more info at the bottom of the post.

    After creating and writing up my last post on the process to automate the download of 23andme Ancestry Finder data files for your matches, I could not resist working on a way to combine all of those data files into one.

    I figured Microsoft Excel was the best common denominator to use for this process – there are any number of tools I could use to combine the files and work with them at the command line, but that would limit the number of people who could use it.

    So, here’s the quick scoop: My Excel spreadsheet is designed for use with the .CSV data files you have already downloaded from 23andme’s Ancestry Finder. (Again, see my Ancestry Finder Download Tool post for more info on that process.)

    • It will import ALL .CSV data files in a selected folder
    • It will add a column with the name of the 23andme user the data file came from. (It uses the data file name for that, so don’t rename them after you download them!)

    Then it will make you a sandwich. A nice juicy data sandwich.

    Each data row will have the source person AND matching person’s name in it – otherwise you would have a list of a few hundred thousand matches without knowing whom they belonged to!

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  • May9

    22 Comments

    UPDATE (09 NOV 2015): 23andme is retiring Countries of Ancestry, (the tool formerly known as Ancestry Finder) as of November 11, 2015. I’m leaving this blog post out here for posterity, mainly due to vanity and the amount of time I put into creating my Excel sheet. 😉

    But, as mentioned in the previous update: you should be using the tools at DNAGedcom.com. Good luck to you!

    UPDATE (11 July 2013): It has been more than a year since I created this tool and process, and the 23andme site has gone through some extensive changes. I have not had time to test if the process in this post nor the spreadsheet is still working properly with any possible data format changes.

    Feel free to give it all a shot, but I recommend that you may first want to take a look at the DNAGedcom.com site, which has automated things in a much more user-friendly way!

    Ancestry Finder Drop DownIf you are a 23andme customer, you may have noticed that they updated their Ancestry Finder (AF) tool to make it possible to see the matches of the people with whom you share genomes. You can also download this data in comma-separated-variable (.csv) format.

    That. is. great. stuff.

    I’m sure that people will soon come up with interesting new ways to triangulate their genetic matches and learn more about their ancestry. But, there is one problem: If you are sharing your results with a few hundred people and want to get all of their AF data files, it takes a drop-down selection, wait a few seconds for AF to reload, then a button click and a Save File As click FOR EACH PERSON IN YOUR LIST.

    Holy carpal tunnel.

    I suppose 23andme might make it possible within their system to get them all at once which will make this all moot. But, I thought there must be a better way to get all of these data files and I found a slightly clunky, yet completely workable method.

    There may be more elegant ways to do this, but for now I created an Excel spreadsheet that will help you get you all the data with only a bit copying and pasting – along with some help from a Firefox add-on.

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