The Little Scottish Cluster is a group of R-L21 men who share a recent common ancestor.  Age estimates for this group generally range from 1000 to 1500 years -- well before the adoption of surnames.  As such there are a wide variety of surnames in the project.  The majority of men in this group, but not all, trace their ancestry to southern Scotland, where their common ancestor is believed to have lived.

The haplotype of the common ancestor (the LSC ancestral haplotype) has been passed down, father to son, for all of the men in the project.  This is the key to identifying men who belong to this cluster, or any other STR cluster.  Any unusual characteristics of the ancestor's haplotype are passed down, almost exactly, to his male descendants.  By examining the haplotype for these unusual characteristics, we can determine if a candidate is likely a Little Scottish Cluster descendant or not.

There are also a number of SNPs associated with the Little Scottish Cluster. The men in the Little Scottish Cluster test positive for the SNP CTS2187/S190, which can be ordered as an advanced test. Some families in the Little Scottish Cluster now have additional SNPs which define their lineage.

There is another cluster of men known as the Scots Cluster, with which this group is often confused. They are a much larger group of men, with a very different haplotype. Their project website is the R-L1335 project.

Within the first 25 markers, the most distinguishing feature of the Little Scottish Cluster haplotype is the odd value of DYS464a = 13.  Another group, Irish Type III, also share this feature, but differ on other markers.  The most distinguishing marker overall is DYS 590, for which the members of the LSC have the value 9, rather than the common value 8.  This marker is only in the 67 and 111-marker tests.

The table below gives the full set of characteristic markers, as well as the common R-L21 value.

There are several Little Scottish Cluster modal haplotypes on ySearch, put there by various researchers for a number of purposes:

• KXNRA - Maintained by Kirsten Saxe - The full 67-marker Little Scottish Cluster modal haplotype.
• U8HJZ - Maintained by Kirsten Saxe - The 37-marker version of the Little Scottish Cluster modal haplotype.
• RRC7B - Maintained by Steve Colson - Used as a research tool to explore possible LSC connections.

Haplogroup

There are several SNPs of relevance to the LSC. In order of age, oldest to youngest, they are L21, DF21, S3058, S424 and S190.

• L21 is the most downstream SNP currently on the Y tree that FTDNA uses.  In FTDNA notation, it corresponds to the haplogroup R1b1a2a1a1b4.  All men in the LSC would test positive for this SNP, if they were to test for it.
• DF21 is a SNP downstream of L21.  This means that all DF21+ men are also L21+, but not vice-versa.  All LSC men would test positive for this SNP.
• S3058 is a SNP downstream of DF21.  All men in the LSC that have tested for this SNP, have so far tested positive for it. There are men outside of the LSC who are also positive for this SNP.
• S424 is a SNP downstream of S3058.  All men in the LSC that have tested for this SNP, have so far tested positive for it.
• CTS2187/S190.  Depending on how you wish to define the LSC, this SNP can either be viewed as defining it, or splitting it.  With the notable exception of Reddin, all other LSC men who have tested for this SNP, have tested positive for it.  Reddin belongs on a small branch parallel to the primary LSC cluster.  His haplotype however, is still very much LSC like, including the marker DYS590 = 9.  Some people have referred to Reddin as a Little Scottish Cousin.

Further analysis and background information can be found at the Little Scottish Cluster webpage.