What is the Little Scottish Cluster?
The Little Scottish Cluster (LSC) is a group of families who share a recent Y-DNA (male line) genetic relationship. The most recent common ancestor (MRCA) of this group lived in Scotland about 1200 years ago. The male members of this cluster have similar haplotypes which are distinctly different from other men. The members also carry the SNPs S424 and S190 which are unique to this group.
Genetic genealogy has opened up a new avenue to explore family histories. Genealogists are no longer limited by the existence of historical documents, and are given direct access to the ancestry written in their our genes. Testing DNA itself really does put the gene in genealogy. Paper genealogy can only be used as far back as paper records exist. Beyond that, we have our genetic heritage to rely on.
The genetic testing used in genetic genealogy relies on the identification of two different types of markers, SNPs and STRs. SNPs are mutations at a single position in the DNA, and have a very low mutation rates. They are used to identify branches of our family tree, hundreds or even thousands of years old. STRs are short repeated segments of DNA. They mutate much more quickly than SNPs, and can be used to idenfity branches of a family on timescales relevant to genealogy.
Family Tree DNA is the most widely used testing company for genealogical purposes, and I'd recommend any STR testing to be completed with them. Their large database enables easy comparison to others. Other companies do exist however, and results can be uploaded to shared databases like ySearch for comparision to men tested at different companies.
ScotlandsDNA doesn't test for STRs at all, but only for SNP markers. ScotlandsDNA tests for a number of SNPs which are relevant to the LSC. In particular, they test for S424 and S190, which were discovered there. If you test positive for either of these SNPs, then you are a part of the LSC and I'd invite you to get in touch with me so that I can track your results along with the other LSC men who have tested at FTDNA.
The LSC was discovered with STR marker data, and SNPs have now be found which are specific to this group. A characteristic pattern of STR markers distinguish them from other men. Their nearest matches (given sufficient markers) are always other men in the cluster.
The concept of a STR cluster is not well defined, but is geneally related to the distinctiveness of its member's haplotypes. Convergence issues aside, the haplotypes should be very similar to each other, and very different from everyone else. How this situation comes about is a part of their history. Each cluster has one founder who is the most recent common ancestor (MRCA) of the cluster. This founder's haplotype, often referred to as the ancestral haplotype of the cluster, may not have been very different from the men around him at the time he lived. Over time however, other parallel lines have died out, leaving a group whose marker values are now very different from everyone else outside of the cluster.
The founder of the Little Scottish Cluster lived over a thousand years ago and well before the formal adoption of surnames. His descendants now carry a wide variety of surnames. Some of these surnames were adopted early on and have a large number of members. Others were adopted much later leading to a much smaller family. Some of these surnames have remained in their native Scotland, while many of them have spread to Ireland, England and beyond.
Within each of the surname groups, the members may be able (at least in principle) to trace their ancestry back to the first member of the LSC to adopt that surname. Although there may be LSC men who carry a particular surname, in general, not all men with that surname will belong to the LSC. In most cases, each surname will have at most one LSC lineage, but a couple exceptions do exist. Conventional paper genealogy as well as analysis of each member's haplotype can be used to reconstruct each surname's family tree.
Assuming you are a member of this cluster, an issue we will discuss in the next section, we have only genetic genealogy and the occasional historical record to guide us in understanding our larger family. By reconstructing the family trees for each of the members various surnames, and then fitting these pieces together, we can hopefully reconstruct our larger family tree.