Posted by Sappho on November 7th, 2013 filed in Blogwatch
One of the difficulties of genetic genealogy is distinguishing between which shared segments actually indicate shared descent in a genealogical timeframe (called “Identical By Descent”), and which are from longer ago, perhaps only pointing toward being part of a shared population (called “Identical By State” or sometimes “false positives”). Different DNA testing companies use different algorithms for trying to supply good matches without too many bad ones. Dienekes Pontikos has a post on a recent article on Dealing with false positive IBD segments. (or “Reducing pervasive false positive identical-by-descent segments detected by large-scale pedigree analysis”).
X DNA has a complicated pattern of inheritance, since men only get it from their mothers, while women get it from both parents. Here are some links on X DNA inheritance:
I meant to link a post explaining why so many of your cousins may turn out to be at the distant end of the ranges your DNA testing company gives for how related they should be, but I can’t find where I saved the link. The gist of it, though, was this point: We have many, many, many more distant cousins than close ones. So, if you share, say, 11 cM with a cousin, that’s enough that you can hope to find a traceable connection, but, of all the people who preserved that 11 cM segment, if your ancestors were reasonably prolific, your more distant cousins will still wind up outnumbering your closer ones.