This page discusses the defining mutation for haplogroup G, called M201.   

So far, every tested G person has belonged also to a subgroup of M201.  The M201 mutation 
actually is one of about 300 we have identified that are found in all G persons, and it is 
unknown which was the first to develop.  

Locations of the Origin of Haplogroup G

Those 300 shared mutations seem to represent about 18,000 years during which a G family
group roamed about during the hunter-gatherer days.   Hunter-gatherers could be very
mobile in following migrating animals, and climate changes would have forced them farther 
south at times.    Various studies attribute the homeland of haplogroup G to the Middle
East or Pakistan or somewhere in between.  This speculation seems partially based on 
where G persons live today and where men in other haplogroups derived from the same 
mother group live today.  Southwestern Asia seems the center location of haplogroup G
in the world, and the men we have found with the most diverse types of G haplogroups so
far identified have Armenian ancestry.  Considerable diversity of G subgroups could
point to the longest period of residence.   But no one knows for sure where the small band
of G ancestors was living in the period before today's subgroups developed.  

Unmentioned in the published studies is a possible role for the southeastern quadrant of
Asia in spawning the original G men.  F is the mother group of G, and F is heavily 
concentrated in southern Asia.  In addition, G is now known as the earliest branch
off of F.  Then, one of next offshoots, haplogroup H, is also heavily concentrated in
southern Asia.  One study has also suggested that G may share an early branch with 
F2, which seems a mostly s. e. Asia haplogroup.  

The best way to date G and its subgroups would be by testing the DNA of ancient 
skeletons and dating the bones by proven dating methods.  The oldest Y-DNA so
far identified is about 10,300 years old.  The oldest G skeleton (of unknown G type) is
a bit over 7000 years old and belongs to a specific G branch.

Dating Haplogroup G and M201

In earlier studies, G was dated at most to about 21,000 years ago.  There are actually
two aspects to this.   One date would be that of the oldest shared ancestor of all living
G persons, and the other date would be the date the ancestor of G persons formed a
separate branch off of haplogroup F.   The existence of 300 mutations shared by all
G men suggests that comparing information from today's men will not tell us when 
the very first G man lived because of the gap in time without any branching 
represented by the 300 mutations.  

But if a mutation rate for permanent Y mutations (the SNPs) can be established,
then the 300 mutations of the very early pre-branching period can be translated into
a length of time.  And that is how the approximate 18,000 years figure came to be.

This dating is based on a new method of dating, that of counting SNP mutations,
This first started to have practical uses in late 2012.  And that study (Wei)
suggested that all the haplogroups that branched from haplogroup F (including G)
diverged from F about 46,000 years ago.  This study needs to be done again with
all the haplogroups included to confirm these findings, but we are here using
46,000 years as the working model.  In Aug 2013, Francalacci et al. proposed 
calibrating mutation rates instead according to when Sardinia was first settled.  Since
there is no guarantee that the original settlers had the haplogroups they suggested,
this seems less appealing.  In this over 76,000 years is suggested as the period
in which G separated from F and all dating used on this site would have to be
doubled if Francalacci is correct. 

Poznik et al. in 2013 showed that haplogroup G is the oldest of the 
haplogroups to branch from haplogroup F.  Haplogroups H, I, J, K, L. M, N,
O, P, Q, R, S and T all branch separately and later. 

Older Dating Methods

For a decade or so, the standard dating method used in population genetics 
studies was based instead upon the number of mutations in STR markers.  The
problem with these is that any marker can subsequently mutate back to its
original value thus hiding two mutations.  And this commonly happens.  To 
overcome this problem, a Russian scientist developed a complex formula.
But using marker mutations to calculate time has many drawbacks.  The
validity of the formula seems to break down with dating of recent relationships, and this
prompted some scientists recently to use a method for recent time that presumes there are
yet no hidden mutations. And the validity of the formula gets more difficult to evaluate
the farther back in time one goes.   So it is desirable to eliminate this method of
using marker mutations if the SNP counting methods proves more reliable, as

Haplogroup G Maps

This is the most accurate map yet of the distribution of M201, namely all haplogroup G persons
living today.  But any such map is misleading in that multiple migrations by G subgroups created 
this pattern:
http://en.wikipedia.org/wiki/File:Haplogrupo_G_(ADN-Y).PNG  It seems to overstate the percentage of
G in n.w. Africa, in Switzerland and the Basque area of Spain and understate the percentage
in Turkey.

This map (at top) from a 2012 study by Rootsi et al.
provides a better perspective for Africa, but every locale less than 7.5% M201 is almost invisible 
on this map.  And the software's joining of several locations eliminates the checkboard
reality of M201 percentages in locales in places like Italy.

The map showing all locations where G men in the project report ancestry can be
found at:
Choose the ALL feature at the top left of the map.  Members tend to be mostly from
Europe, and this understates the actual African and Asian coverage of G.

This map shows the diversity of haplogroups in s.w. Asia.  Though some sites are not
included, G shows in the mix mostly in an area from Turkey, n.e. to Kazakhstan, down to 
southern Iran and back to Turkey.  Increase magnification to 150%.

This has the most detailed map (figure 1) of M201 percentages in Iran and adjacent areas:

Source Information

The Zhivotovsky formula is relied on to calculate times to shared ancestors by many
but the new method of counting of SNP mutations in whole Y sequencing from Wei and
others in 2012 may be more accurate:

This study seemingly identified the oldest Y-DNA haplogroup  found in a skeleton 
(10,300 years ago in an Alaska skeleton -- haplogroup Q)

The National Geographic Society is very vague on the location of haplogroup G in early
migrations in Atlas of the Human Journey

Evidence for mobility of men in the Stone Age.

The study dating the oldest G skeletons so far found (only at 7000 yrs ago in Spain):

The Francalacci study from 2013 proposed that each SNP found in the most reliable areas of the 
Y chromosome represents a 200-year period rather than the 100 yrs used by other authors.

Poznik and others in 2013 showed that haplogroup G is the oldest branch off of F.