Ashkenazi Y-DNA Haplogroup G

Based upon the methodology posted here and using the sample set described here, as of January 2019 it appears that there are three ancestral Y-DNA lines in haplogroup G in the Ashkenazi Jewish population: (1) the G-FGC35913 subcluster of G-BY764; (2) the G-FGC31712 subcluster of G-FGC249; and (3) the G-L201 subcluster of G-L1324.  Trees for each of those clusters are posted below.

G-BY764

Upstream SNPs: 
M201>L89>PF5721>M377>BY794>BY764
TMRCA (YFull Tree)
G-M3124: 3,200 ybp (2,000-4,800 ybp @95%) (G-M3124 is one level above G-M283 on the YFull tree and therefore may be at the same level as G-BY764)
G-Y15563: 1,050 ybp (750-1,400 ybp @95%) (G-Y15563 is at the same level as F-FGC35913)
TMRCA (JewishDNA.net)
G-M377 (AB-056): 899-1058 CE (@95%)

The G-FGC35913 cluster follows the same pattern as many of the larger Ashkenazi clusters, with (1) a shared direct male ancestor dating back to about the second half of the first millenium CE, as evidenced by initial branching during that time frame; and (2) substantial branching within those subbranches that presumably dates back to the time when the Ashkenazi population began its massive expansion out of a small bottlenecked population, about 700 to 1,000 years ago.  

G-FGC249
Upstream SNPs: 
M201>L89>P15>L1259>L30>L141>P303>L140>PF3346>PF3345>CTS342>CTS8476> CTS5990>CTS7045>Z3428>Z26414>FGC7477>FGC264>Z6028>FGC249
ISOGG Tree (2019): G2a2b2a1c1a1b1a1a1
TMRCA (YFull Tree)
G-FGC228: 1,250 ybp (750-1,800 ybp @95%) (G-FGC228 is at the same level as G-FGC249)
TMRCA (JewishDNA.net)
G-L140-FGC249: 576-947 CE (@95%) 

Branching is shown here starting at the G-FGC249 level to indicate that the G-FGC263 and G-FGC31715 branches share a direct male ancestor, who presumably lived in the Near East.

The G-FGC31715 cluster follows the same pattern as many of the larger Ashkenazi clusters, with (1) a shared direct male ancestor dating back to about the second half of the first millenium CE, as evidenced by initial branching during that time frame; and (2) substantial branching within those subbranches that presumably dates back to the time when the Ashkenazi population began its massive expansion out of a small bottlenecked population, about 700 to 1,000 years ago.  (Note that, for example, the G-FGC31708 branch out of the G-FGC31715 level leaves behind a G-FGC31715* branch, and that, as a result, the tree above shows branching below the G-FGC31715 level even though it shows only a single SNP downstream from G-FGC31715.)

The fact that the sample set includes a large number of G-FGC263 men but no branching below the G-FGC263 level suggests that few if any men in the G-FGC263 cluster have done Big Y testing.

G-L1324 (G-L201 subcluster)
Upstream SNPs: 
M201>M285>CTS11562>BY1124>Z3353>L1324
TMRCA (YFull Tree)
G-L1324: 4,800 ybp (4,100-5,600 ybp @95%)
G-L201: 500 ybp (175-850 ybp @95%)
G-L1323: 750 ybp (550-1,000 ybp @95%)
G-Y14914: 1,600 ybp (1,000-2,200 ybp @95%)
TMRCA (JewishDNA.net)
G-M342-L201: 1,106-1,536 CE (@95%) (for G-L201, one SNP downstream from G-L1324)

Branching is shown here starting at the G-L1324 level to indicate that the four branches below that level share a direct male ancestor, who presumably lived in the Near East.

The G-L201 subcluster is the only subcluster within the G-L1324 cluster that includes men in the sample set.  The fact that the sample set includes a significant number of G-L201 men but no branching below the G-L201 suggests that few if any men in the G-L201 cluster have done Big Y testing.  Because there are no men in the sample set who belong to the G-L1323, G-Y14914, or G-Z44585 subclusters of G-L1324 but the total number of men in FTDNA's database in those clusters is small, it is unclear whether any of those clusters may be Ashkenazi.

Y-DNA SNPs Not Appearing on Trees Posted Above
In addition to the SNPs posted above, there are a number of SNPs identified through the methodology used on this website that do not appear in any of the trees posted above.   In some cases, primarily with regard to SNPs reported by Family Tree DNA based upon the results of Big Y testing or Geno 2.0 testing, the reported SNPs are ancestral to the SNPs set forth in one or more of the trees above; if the tested man is Ashkenazi on his direct male line, Big Y testing would likely determine that he belongs to one of the clusters set forth above. In other instances, it is possible that SNPs identify a small and/or undertested Ashkenazi cluster; further testing or information may identify such clusters.   Often, because the methodology used herein to identify potential Ashkenazi SNPs is overinclusive (especially for the 50 cM cohort but also, on occasion, for the 80 cM and 100 cM cohorts), SNPs set forth below do not reflect Ashkenazi (or Jewish) ancestry on the direct male line.  Finally, there are some SNPs (identified with "N/A") that do not appear on FTDNA's Y-DNA haplotree at all.
Upstream SNPs.  The following SNPs in the table above (identified in red) are upstream from SNPs found in one or more Ashkenazi Y-DNA clusters: CTS5990, L140, L30, M201, M285, M377, P15, P303, PF3345, and Z3428.  

If men who are reported based upon STR or Geno 2.0 testing as having these SNPs are of Ashkenazi descent on their direct male line, there is a high probability that such men belong to one of those Ashkenazi Y-DNA clusters.  However, a large proportion of the men reported as having these terminal SNPs are not of Ashkenazi descent on their direct male lines.

Downstream SNPs that may reflect an Ashkenazi Y-DNA line.  The following terminal SNPs in the table above (identified in blue) do not appear in the Ashkenazi Y-DNA trees posted above, but may reflect an Ashkenazi Y-DNA line: G-L830, S-11415, Z18606, Z43085, and Z44224.  

Other SNPs.  With the exception of the SNPs that are not on FTDNA's Y-DNA Haplotree (identified with "N/A"), it is unlikely that men reported as having terminal SNPs other than the upstream SNPs identified above are of Ashkenazi descent on their direct male lines.