GENEALOGY-DNA-L Archives

Archiver > GENEALOGY-DNA > 2010-11 > 1288881610


From: "Lawrence Mayka" <>
Subject: [DNA] FTDNA haplogroup prediction more sophisticated than before?
Date: Thu, 4 Nov 2010 09:41:40 -0500


Many years ago, FTDNA explained its haplogroup prediction algorithm in an
issue of Facts & Genes. Since then, the algorithm has been tweaked, but I
presumed that it still:

- Looked at only the first 12 markers, perhaps because 12-marker tests are
still available

- Ignored geographical and ethnic information, perhaps because undocumented
adoptions (NPEs) are always a possibility

- Did not weight one marker over another, perhaps because such weighting is
itself potentially haplogroup-dependent.

Months ago, however, someone pointed out to me that the same 12-marker
haplotype occasionally produced a slightly different prediction (e.g., R1a
vs. R1a1). I verified that, but presumed that we had merely caught the
database in the middle of a minor algorithm tweak.

However, it is now obvious that FTDNA is doing _something_ more
sophisticated. Consider this actual 12-marker haplotype:

12 22 14 10 13-14 11 15 11 13 11 29

This individual's Y-DNA Haplotree/My Matches page shows no exact matches
(with a confirmed haplogroup); but at 1 step away are:

I1 : 5
J2 : 6
J2ab1 : 3

At 2 steps away are:

I : 1
I1 : 117
J1e : 1
J2 : 20
J2a : 1
J2a4b : 4
J2a4b1 : 10

As far as I know, until recently this case would definitely have merited a
SNP Assurance test. But instead, FTDNA's haplogroup prediction is J2.

The individual's next two marker panels (markers 13-37) make clear that the
prediction is correct, but the question is: How did FTDNA arrive at that?
Is FTDNA now using more than 12 markers for its haplogroup predictions? Or
is FTDNA giving extra weight to DYS388? Or has the algorithm been altered
in some other way?


This thread: