I have never answered Carkeet's conclusions and I'm not now but 
I will say one thing. He based a lot of his conclusion on the assumption that I had put up a family tree and that is how I came up with the Clemens/Langdonlinks. Now Barbara is addressing that same issue. 
I had NOT attached a tree to my DNA for the first several years. The DNA matches I got with Clemens and Langdon were sent to me organically by Ancestry and FTDNA (who, at the time, didn't have trees.)
It was only after getting over 100 matches that I attached a tree. 
Regards,
Susan Bailey

Sent from my iPhone

> On Jan 9, 2017, at 10:26 AM, Barbara Schmidt <[log in to unmask]> wrote:
> 
> Hal --
> 
> David Carkeet's research on the flawed methodology used to establish DNA
> connections to Clemens via ancestry.com family trees was the game changer.
> His essay on his months long research and first hand experiences in working
> with the DNA reports is online at:
> 
> http://www.twainquotes.com/Carkeet/AncestryReport.html
> 
> In a nutshell, anyone can plug in a false or inaccurate family tree at
> ancestry.com after submitting a DNA test, and the ancestry.com database
> will generate a list of people who are also related to people in the tree
> one believes is their own tree.  Just about anyone can be distantly related
> to someone else who ties in to the Clemens family tree in some fashion if
> the family tree branches are traced back far enough.  From Carkeet's report:
> 
> "... 'What you are seeing is the result of endogamy, intermarriage within a
> population group. In the year 1700, the population of the United States was
> approximately 250,000 people.' In other words, it is a small world. Or,
> more to the point, it was a small world, with so few people in the pocket
> of immigrant history that I share with my matches that if I select a
> specific name from the past (in this case, with my false genealogy, an
> ancestor of Samuel Clemens), some match of mine from among my more than
> 6,000 matches will descend from that ancestor."
> 
> Barb