A Relationship Outlier

Blaine Bettinger runs the Shared Centimorgan Project in which he's collected thousands of data points for amount of DNA shared between people with known relationships.  He can give a range of DNA which has been observed to be shared for people with specific known relationships.  If you have a new DNA match, you can see how much DNA you share with that person and use Blaine's chart to identify potential relationships that are possible with that person.

Shared cM Project.  From http://thegeneticgenealogist.com/wp-content/uploads/2016/06/Shared-cM-Project-Version-2-UPDATED-1.pdf.  Used with permission.

An Issue With Lazarus

I've written about Lazarus before, a tool available via GedMatch which allows for you to reconstruct a partial genome of a deceased ancestor using living relatives' DNA.  Lazarus requires you to put direct descendants of this ancestor into Group 1 and other relatives of that person in Group 2.  The idea is that if a segment is shared between a descendant of that individual as well as by one of his or her cousins, that segment can be attributed to the deceased ancestor (weeding out segments that come from other ancestors of those in Group 1).  Particularly when dealing with endogamy, there could be extra segments introduced, but that's not the point of this post.

Enough of my relatives have tested that I've been able to create Lazarus kits for multiple ancestors.  But I've been noticing some odd results for many of them.  Here's one example, in trying to recreate my grandfather's genome.

My Uncle's Shared Segments with Don

Long Segment--But No Close Connection

Particularly when dealing with endogamy, where it is difficult to tell apart cousins who are actually relatively closely related as opposed to those who are very distantly related in multiple ways, a good metric to hone in on matches who may actually be related in genealogically-traceable time is the size of the largest shared segment of DNA.  I've had good success finding people who are actually related or at least are from a very close geographic proximity to one of my ancestral towns, even if we can't find the actual paper trail connection.

But sometimes those large segments may be passed down for many generations.  Several of my kits--all related on my maternal grandmother's side--share the same large segments with several kits administered by a man named Luc.

Luc's Tested Family Members--With DNA Shared With My Relatives

Another Generation of Diamonds?

I had tested my father's Y DNA several years ago.  As is not uncommon for Jews (who have not had surnames for too long), he had no matches with the surname Diamond besides his second cousin who I'd also tested--but had lots of matches with lots of people with Jewish surnames.  But then about 2 months ago a new match popped up--with the surname Diamond.

The first match is Uncle Leibish's grandson.  The second is this new match