There are probably many readers on here who get a little lost when the topic
turns to SNP's, haplogroups and the different names that haplogroups have.

A SNP (pronounced 'snip') is a Single Nucleotide Polymorphism.  This is a
fancy name for describing a change (mutation) in just one of the letters in
DNA.  For example, this could mean a DNA strand that once read G at one
location has been changed to A.  When a new son is born, his Y-chromosome
will also have the letter A at this location, as will his sons.  Thus, this
new mutation is passed down from generation to generation.

(Just to re-cap, SNP's are not the same as STR's (Short Tandem Repeats).  It
is the STR's on your Y-chromosome that the genealogy/DNA labs commonly
test).

This type of SNP mutation happens so rarely at any one place as to be
unique.  The rate at which these occur is on the thousands of years scale.
Because of this we can deduce lineages that give hints to human evolution
and migration.  Knowing your haplogroup can give you an idea of the ancient
(read Palaeolithic and Neolithic) migrations of your paternal ancestor.
It's not going to help with that 3rd cousin once-removed connection you are
having trouble making, but most find an insight into the journeys of our
ancient ancestors fascinating.

At this point it is probably worth taking a look at the tree drawn up by the
Y-Chromosome Consortium, which is found at
http://ycc.biosci.arizona.edu/nomenclature_system/fig1.html

The 'root' of the human Y-chromosome tree, shown by the arrow, was deduced
from studying the Y-chromosomes of our closest genetic relatives i.e.
orang-utans, chimpanzees and gorillas.  As you move from left to right, you
can see several branches (or clades).  Each branch is defined by a SNP.
Dependent on which SNP's are detected, you can follow the branches down
until you reach the twigs - in this tree the twigs are the haplogroups, of
which there are currently 153!!

You might notice that some of the branches have more than one SNP associated
with it.  For example, next to the root of the tree there is a branch
defined by four such SNP's; SRY10831a, M42, M94 and M139.  These are simply
branches that can be defined by more than one SNP, but essentially give the
same result.

OK, let's take a look at the right hand side of the tree, the haplogroups.
Can you see the column that starts with A1, A2*, A2a, A2b and goes all the
way down to R1b8?  This is the NEW nomenclature system which the scientific
will have been using since it was published.  Just to the right of this
column, there are a further 7 columns.  These are the old nomenclature
systems.

For a bit of an historical background, different labs around the world
discovered different SNP's.  Because a lot of hard work went into
discovering these SNP's, the researchers tended to form their own groups and
keep the techniques and results to themselves for a while.  When these
different groups came to publish their scientific articles, they all had
different naming systems.  Directly comparing the results in two different
papers was therefore very tricky.  This is where a larger consortium of
researchers came together, called themselves the Y-Chromosome Consortium
(YCC) and began to decipher the work from the different groups.  They came
up with the tree that you see today which has helped standardize everyone's
work.

Confusion arises when people refer to the old names.  For example, what we
now call R1b, used to have the haplogroup names of 1, IX, 1L, 44, Eu18, H14
and also D, entirely dependent on which scientific paper you are referring
to.

So the new standard nomenclature system is very handy if everyone sticks to
it.

If you've had your Y-chromosome analysed, you've probably had your STR's
measured and your results came back as a haploTYPE (all those DYS and GATA
markers!).  The good thing about this test is that not only can you use it
to test your recent genealogical problems, but your haploTYPE is often a
very good indicator of what your haploGROUP is.  There is usually quite a
good correlation.

A good example is the haplotype referred to as the Atlantic Modal Haplotype
(AMH).  The AMH is so called because it is very common haplotype on the
Atlantic coast of Europe (i.e. in Portugal, Spain, France, Ireland and the
UK).  This AMH is also very common in people who are in Haplogroup R1b
(which includes R1b*, R1b1, R1b2, R1b3, R1b4, R1b5, R1b6, R1b7 and R1b8).

So if your haplotype is the AMH:
DYS19  = 14
DYS388 = 12
DYS390 = 24
DYS391 = 11
DYS392 = 13
DYS393 = 13

then you can say with fairly good accuracy that you are in R1b.

The origins to this R1b haplogroup are thought to be back in the Upper
Palaeolithic times.  Around 18,000 years ago when the last big ice-age was
at it's maximum, the people populating Europe at the time (stone-aged
hunter-gatherers) had to take refuge away from the ice and retreated back to
South-Western France, Spain and Portugal (even though the Pyrenees had thick
ice on them).  There were also pockets of people in the Balkans and up in
the Ukraine.  When the ice finally retreated (around 11,000 years ago),
these Iberian/French people, who had acquired the mutation that defines them
as R1b, moved across to Italy and also up the Atlantic coast, eventually
making it to Britain.

This migration theory is still being investigated, but the genetic evidence
is quite compelling.  For those who wish to read up on this further take a
look at:

http://www.sciencemag.org/cgi/content/full/290/5494/1155?

which should take you to a paper called -
The Genetic Legacy of Paleolithic Homo sapiens sapiens in Extant Europeans:
A Y Chromosome Perspective
which has been mentioned a couple of times before on this list.

(you may have to sign in to read this and it uses an old nomenclature
system, but it is free!)

If you wish to know your haploGROUP, one way is to compare your haploTYPE
with others at Ybase (http://www.ybase.org).  Many FTDNA customers who have
had their Y-DNA tested have also had their haplogroup predicted from their
results, based upon a comparison with data held at the University of
Arizona.  Fortunately, many of these customers have also entered their
results AND haplogroup at Ybase, so you can usually find your own,
especially if you have European origins.

If you have time to add your results to Ybase too that would be great.  It
is free for everyone to use and only works if people help it grow by adding
to it and spreading the word.  There have been several useful connections
made so far and this should only increase as it becomes larger and
encompasses more surnames and haplotypes.

Most of the haplotypes at Ybase are 'European'.  They are of course found
elsewhere.  This is usually due to the events such as the Spanish conquest
of South America, where the males eventually integrated with the native
population.

Hope this helps shed some light on the whole haplogroup thing.

Kind Regards
Alastair