Understanding Y Haplogroup R-FT256640 and Subclades

Date: [unknown] [unknown]
Location: [unknown]
Surnames/tags: McCool Y-DNA

This research project is intended to help McCool descendants understand Y-DNA Haplogroup R-FT256460, its subclade R-FT303841, and its parent haplogroup, R-FGC13495.

R-FT256460 is a (northern) Irish R1b subclade that falls below R-P312, R-L21, R-DF13, R-L513, R-S6365, and R-FGC13495. It is located at position 9030463 on the Y chromosome, where expected nucleotide G switched to A.

When a new person takes a Big Y-700 test, they usually match to many variants (SNPs) that have been discovered before. They usually (but not always) have one or more variants that haven't yet been seen in other tested men - called private variants (PVs).

Here's how the naming conventions work:

• private variants are unique to a single tester; they are referred to by their location on the Y-chromosome, such as 9030463.
• when a second person matches the previously private variant, the testing company changes it to a named variant, such as FT256460. The first two letters, FT, indicate the naming organization (in this case Family Tree) and the number shows that this was the 256,460th named variant with that prefix. Because FamilyTree is the largest Y DNA tester, they have used multiple prefixes over the years.

Variants occur randomly, but are somewhat uncommon. In the Y chromosome areas examined with the Big Y-700 test, a variant occurs about every 83 years (so once every two to three generations). Variants are then passed down to all future male generations. Note that two or more variants can occur in a single generation, but this is unusual.

By examining which existing variants a tested person has, FamilyTreeDNA can determine the sequence of newly discovered variants.

There are often groups of named variants that are shared by everyone who has one of them. These are often called equivalent SNPs. There is no way to determine which of the variants took place first until a future tester has one of them (or more) but not the others.

FT256460 is currently part of a group of four equivalent SNPs. Every tested McCool in this line (so far) has inherited all four variants. For the sake of convenience, FamilyTreeDNA assigns one of the four as the name of the group until/unless the group is eventually broken down further.  

R-FT256460 Hierarchy

As of November 2023, there are three Big Y-700 tested matching men with McCool paternal-line ancestors in this line. In test-date order, their first initials and FTDNA kit#s are:

• G: 926286
• S: B141731
• D: BP13537

These three men also match to five McCool men who tested at the following lower levels:

• Y-25: none
• Y-37: (1)
• Y-67: (3)
• Y-111: (1)

If any of the five were to ugprade their test to Big Y-700, they would fall somewhere into this hierarchy (although likely to create a new branch.)

When the first McCool in this group took a Big Y test (G: kit# 926286), he matched to a long series of named variants ending in the R-FGC13495 equivalent group. He also had about six private variants that no one else yet matched. He was assigned R-FGC13495 as his haplogroup.

The second Big Y-tested McCool in this line was S: kit# B141731. He matched four of those six existing McCool private variants, and had three new private variants of his own. The four private variants were then Named - and the two McCools received a newly created haplogroup R-FT256460.

The third Big-Y tested McCool in this line was D: kit# BP13537. He matched all of the named variants in the FT256460 group. He matched one of S's private variants, 8389232, which was then named FT303841. He did not match S's other two private variants; he had three new McCool private variants of his own.

S and D were given the new haplogroup, R-FT303841. G did not have that variant, so his haplogroup remained at R-FT256460. This tells us that S and D share a more recent McCool ancestor with each other than they do with G.

This chart summarizes the preceding information and is further explained below:

R-FT25640 Branches: Nov 2023

R-FGC13495: The large gray area at the top shows the ten equivalent SNPs that currently make up the R-FGC13495 haplogroup. The column just to the right of it shows the position of the SNP on the Y chromosome and the change that occurred. For example, BY43659 is located at position 20067186 and reflects a mutation from the previous value of C to G. We don't know the order of the SNPs within the block. The most recent ancestor in the block was born about year 1207 (but could vary from years 1075-1320 - or even 935-1420), almost certainly in Scotland. This was far before surname standardization, so descendants of this haplogroup have a variety of surnames - especially McPherson (and spelling variants).

R-FT256460: The middle blue area shows the four equivalent SNPs that currently make up the R-FT256460 haplogroup. All three men who carry these variants have paternal McCool ancestors. The most recent ancestor in this block was born about 1686 (but could vary from 1590-1766 or even 1479-1829). However, the latest ancestor in this block goes hundreds of years earlier. It's possible that a non-McCool (from before surname standardization) will eventually prove to descend from one or two of these SNPs.

R-FT303841: the orange section at the bottom left shows the single haplogroup named when D tested in April 2023. The most recent common ancestor of S and D was born about 1739, but this could again vary significantly.

Frequently asked questions