AncestryDNA and the Longest Segment Match

Gradually Ancestry is releasing additional information about our DNA matches. While there still isn't a chromosome browser the longest segment in common with matches is now listed along with the total DNA and number of segments matched.

Why is this important?

  Debbie Kennett writes:

"This is particularly important for people who are descended from endogamous populations. Knowing the length of the longest segment you and a DNA match have in common can help determine if you’re actually related. The longer the segment, the more likely you’re related. Segment length is also the easiest way to evaluate the difference between multiple matches that all show the same estimated relationship."

Blaine Bettinger writes:

"Knowing the length of the longest segment shared with a match will be enormously beneficial to test-takers with endogamous ancestry. It will allow them to identify, to a degree, matches that share only small pieces of DNA (and thus much older common ancestry) and matches that share at least one large piece of DNA (and thus more recent common ancestry)."

 In an earlier post Blaine has tables with longest segment statistics for different relationships and separate stats for endogamous and non-endogamous relationships. Caution. It's unclear to me, along with many other things, how applicable these stats from 2015 are to results from Ancestry and the way they manipulate the data today.