For more than 10 years, we have made rapid and useful progress in using yDNA for our genealogical research. This work has mainly been through ySTR - "markers" - that are tested by the commercial companies. If you test at FTDNA (like I do), you are familiar with 25, 37, 67 and maybe even 111 markers. A steady increase in the number of markers has helped us refine our understanding of who we match - and who we don't match. We've struggled with "false matches" at 12 and 25 markers, upgraded to 37 and 67 markers to confirm our matches and used shared mutations to identify branching within our genetic family (often called a "Lineage" or "Group")
Now, we seem to be on the verge of genealogical assistance from another part of the y-Chromosome - the SNP (Single Nucleotide Polymorphism). A SNP is a mutation that occurs "once in history" and is passed down to all of the male descendants of the man who first had the mutation. As the centuries have passed, these SNPs have built up in a logical progression that has allowed scientists to catalog them and then deduce their place in the history of man. As the knowledge of SNPs expanded, scientists were able to use them to discern the branches on the "Family Tree of Man" - branches that are called "Haplogroups".
Initially, Haplogroups were assigned letters of the alphabet as the defining SNPs were discovered - so there is no logic in which branch received which name. If you have been involved with the use of DNA for Genealogy for very long, you can remember when Haplogroups were very short - like I1, I2, G, R1a, R1b, etc. After 5 years, my own Haplogroup had lengthened from "R1b" - by one digit - to "R1b1". While we have focused on our marker and surname based research, the identification of SNPs has exploded - which means that Haplogroups have gotten much longer - indicating more and more branching that has been discovered. Currently, my own Haplogroup has extended to R1b1a2a1a1b3c2 - much longer that "R1b1" from the early days!
Despite the explosion of SNPs, the branching still hasn't reached into the marker territory - as a typical Lineage (Group) still has the same Haplogroup as many other Lineages across many surname families. A few Lineages, like my own Barton Lineage I have their own unique SNP - but that is still very rare.
But look out!!!! The SNPs are coming!! I can't visualize whether it will be less than a year, one year, or a "few" years - but it is clear that the time is coming when Haplogroups will be branching within Lineages. We'll be seeing more and more Lineages with their own defining Haplogroup and will also will be seeing multiple Haplogroups with a Lineage. As the SNP research fulfills its possiblitilies, we should see Haplogroup branching tracking into historic times and connecting with our known paper trails.
What will this mean to each of us? It's too early to be certain, but there seems to be a good chance that SNP defined Haplogroups will be able to replace those lost paper trails and allow us to understand how we are related.
I can't wait!