We Share X-DNA But No Autosomal DNA...Now What?

Just like autosomal DNA, there's no rhyme or reason why certain family members receive specific segments or specific amounts and others don't.  X-DNA isn't exactly useless, but it kind of sort of is without autosomal DNA.  So what do you do when you have a match in which you share X-DNA but no autosomal DNA?
Well my story actually started back in 2012 when one of my X-DNA matches reached out to me. This match had over 150 surnames listed on his profile and no tree. (I may write a rant about this later).  My X-DNA match and I corresponded back and forth for several weeks about the nature of our relationship.  He was thoroughly convinced that we were related through his Bass line and to take it a step further he was certain that it was the infamous Bass family that hailed from Norfolk County, Virginia that married into Native American and African families.  Well he certainly had a healthy dose of Native American DNA according to 23andme.  As a matter fact the percentages were in the double digits.  So to me it seemed plausible that he was telling the truth.  There was one little thing that stood in our way.  We really didn't understand the X-chromosome and X-DNA inheritance in males and females.  Another thing that we failed to see, was that we actually didn't share any autosomal DNA.  So at the time I was completely happy with knowing our connection was through our mutual Bass lines, but I couldn't definitively prove it.  Afterall, he didn't have a tree in which I could make the connection. He only regurgitated information that was online without connecting it to his pedigree.

Once I received a better understanding of X-DNA inheritance, I really wanted to know if we shared a set of ancestors other than the female ancestor in which we inherited our X-DNA or if we shared autosomal with other matches in common.  Perhaps our female ancestor provided us with autosomal DNA, but we received different segments.  So how would I know if his was the case?  After all I have a match that has done autosomal testing but really isn't interested in putting it to use.

So what did I do?  I used Gedmatch (although this would probably work on DNAGedcom as well). Here is what I did step by step.  Please note that this is not a fail proof way of finding that common ancestor, however it will put you closer than where you were.

1. I ran a One-to-Many (autosomal) list for both my father's kit and my match's kit.  I knew that my match was a paternal match as he shared X-DNA with my dad.  I copied and pasted both lists into Excel
2. Once you copy the first kit into Excel, add an additional column before Column A (Kit number).  You may label this column "Tester".  In that column please type the name of the person's whose kit you just copied onto the spreadsheet.  Copy and paste (or drag) the Tester's name all the way down the column to the last cell that contains Gedmatch information. 
3. Paste the 2nd kit in the same spreadsheet, just underneath the 1st kit that you copied.  Add the name of the 2nd person in Column A (Tester). Copy and paste (or drag) the 2nd Tester's name all the way down
4. Hide any columns that you don't need or want
5. Sort the list one of two ways:  either sort by Kit number or sort by Gedmatch username
6. Once you have sorted look for the duplicates.  If you are proficient in Excel or have working knowledge of the program, you can write a formula using the "Conditional Formatting" feature or if you're a wiz you can write a regular formula that will find the duplicates.  If you are not proficient in Excel, then you will have to manually look for duplicates the old fashion way, which is go through the sorted list and look for duplicates either by kit number or username.  
7. Highlight the duplicate rows.  If you used conditional formatting formula it will highlight the cells in the color that you selected
8. Once you have found the duplicate kit numbers, make sure that Column A (Tester) contains both names of each tester.  As a way to triple check the results, copy the Gedmatch kit number or username and do a search (Ctrl + F) on the One-to-Many pages of both Tester's list to make the kit number/username copied is actually an autosomal match for both Testers
9. Once you have highlighted all of your duplicate kits (highlight entire row), use conditional formatting feature to sort by the color that you used to highlight the duplicate rows.  This will group all of your duplicates together for further analysis

Kit numbers and names have been altered to protect the identities of Gedmatch users.  

Now that you have a list of kit numbers of the matches you have in common with your X-DNA match, you will need located the chromosome segments in which DNA is shared.

1. In Gedmatch, select the 3D Chromosome Browser tool
2. Enter your kit number (or the person you tested), your X-DNA match's kit number along with the matches in which you have in common.  You will only be able to enter a maximum of 10 kits at a time
3. Once you run the tool you will see which chromosomes and the segment locations that you and you X-DNA match shares with your ICW (in common with) matches. (Please keep in mind that you will not have overlapping segments with your X-DNA match, because if you did you wouldn't need to do the additional analysis as discussed in this post.)

So now that you have the charts from the 3D Chromosome Browser tool, what does it all mean?  It means that although you and your X-DNA match may not share autosomal DNA segments, you do share autosomal DNA with others in which you & your X-DNA match share a common ancestor.  The key is too work with your X-DNA match and your ICW matches to figure out if you share a set of ancestors.  For instance, my ICW match, Tom is a confirmed paper trail and DNA match.  Tom and I share a set of paternal (for me) 3rd great grandparents.  My X-DNA match shares autosomal DNA with Tom also.  This may be a very important clue.

Names and kit numbers have been redacted to protect Gedmatch users' identities

Upon checking the details, my X-DNA match shares a 7.3 cM segment of DNA on chromosome #10 with Tom & my father shares 20.7 cM's on chromosome #1 with Tom.  Albeit the segments are on different chromosomes, there is a possibility that it could come from the same ancestor.  Another possibility is that my X-DNA match and Tom could possibly share DNA from another set of Tom's ancestors in which I am have no biological connection.  If my X-DNA match had a tree, we could possibly find additional clues and maybe find the actual source of our connection.  Currently, I am at a disadvantage in ascertaining this information as my X-DNA match does not have a documented tree.  (Pray for me ya'll!)

The Summary by Chromosome chart will give you a high level summary for matching segments on each chromosome.

So as you see the method is not fail proof, however it may help you get one step closer to finding the female ancestor that connects you and your X-DNA matches.  My next step is to run the triangulation tool to see who else matches Tom & my X-DNA match on the same segment of chromosome #10 and do the same for my father & Tom on chromosome #1.  If and when I get in contact with additional matches, I may be able to find additional clues or an answer.

I'd love to hear what methods you are implemening to find additional clues for your X-DNA matches that do not share autosomal DNA with you or any of the kits that you manage.