Hello List,
I hope you will forgive me if I repost a message I just sent on
another list. It addresses the question of why you would test more
markers. This is a clue to me that I need to create some more FAQs!
===========================
What tests you take depends on what you're trying to prove, along with
a consideration of what prior tests have told you.
Back in the days when FTDNA was marketing only 12, then 25, then 37
markers, most people were simply trying to prove their membership in a
particular family. Even then, it was recognized that, with common
haplotypes, haplogroups, and/or surnames, 37 markers was often not
enough to made a solid determination. In most cases, 67 markers are
currently adequate for supporting a connection to a paper progenitor.
However...
As more and more people get tested, the probability of getting a match
by coincidence rises, and we already have known cases where matches of
61/67 and 64/67 were disproven by deep SNP testing. The problem is
most acute in haplogroup R1b, by far the most common haplogroup in
western Europe. Some 80-90% of men in the British Isles are R1b. If
the surname is also common, great caution is needed before declaring a
match. And this is, by the way, the reason I encourage at least one
male in each family, especially R1b's, to be deep SNP tested.
Once you have proven which family you belong to, whether you go beyond
67 markers depends largely on the detail to which you want to support
your paper pedigree. The more markers you test, the more likely you
are to find "branching" markers, ones that identify different lines in
the family. The best example I have for this, right now, is a
Virginia CORBIN family:
http://dgmweb.net/DNA/Corbin/CorbinDNA-results-HgI1.html#AS2
The branch markers are highlighted in magenta and green; and, if
you'll scroll to the right, you can see how the markers identify these
two branches of the family.
I explain my use of "signature" and "branch" markers in more detail
on
this page:
http://dgmweb.net/DNA/General/SignatureMarkers.html
In terms of supporting the lines of descendants from a progenitor,
there's really no such thing as too many markers -- and for that
purpose, 67 is not enough because, for example, we are not so lucky
with this South Carolina CORBIN family where, except for the two
brothers, we have not yet picked up any useful branching markers:
http://dgmweb.net/DNA/Corbin/CorbinDNA-results-HgR1b.html#SC-Pickens
[We are similarly unlucky with the CARRICOs descended from Peter
CARRICO, 1674 immigrant to Maryland.]
The bottom line is that the more you test, the more you know. Whether
knowing is worth the cost is a personally decision, but of all the
things you can spend money on to advance your genealogy, Y-DNA testing
gives you the most bang for the buck -- and getting results of some
kind is a certainty. I don't even like to think about how much money
I've wasted over the years on books, microfilm, and CDs -- and hiring
professional genealogists -- that yielded nothing.
IMO, it is never wasted money to upgrade your Y-DNA testing though, if
money is an issue, I'll certainly concede that spending money on your
genealogy is definitely a luxury, not a necessity. Also for certain,
any of your descendants who get hooked on genealogy will bless you for
having maxed out your tests. I think of DNA test results as part of
the legacy you pass on.
Hope this helps,
Diana