The St Clairs of Herdmanston were the first St Clair family documented in Scotland during the 12^th century. However, it has never been made clear if they share direct paternal ancestry with the St Clairs of Roslin, who came to prominence in the latter part of the 13^thcentury. They may be two completely different branches, but the data we presently have is inconclusive.

For a while the Herdmanston lineage, previously dubbed “mystery lineage”, was stuck at the P310 SNP, which dates to around 5,800ybp (YFull). However, a number of pioneering members took the giant leap into next generation sequencing and FTDNA’s ultimate Y-DNA test, the Big Y. Things have now moved on. Using the YFull NGS (next generation sequencing) interpretation service, the TMCRA (time of most recent common ancestor) for the Herdmanston lineage Big Y samples has been estimated to date 475ybp (years before present); therefore, a common ancestor around 1541* A.D. Two of the Big Ys analysed by YFull from this lineage are particularly interesting, they don’t have the St Clair surname because both their ancestors were Forresters, a name we see feature in the late medieval St Clair narrative. 

The next task for this lineage will be to identify an SNP within the early middle ages to genealogical timeframe, this will make testing for this lineage much easier and affordable. It can also be used to test out theories concerning their possible origins.

*'Before Present' is calculated to begin at 1950 in the archaeological discipline for the purpose of radiocarbon dating. However, YFull uses a formula of 144.41 years being the average time in between SNPs and 60 for the assumed age of the person. YFull also round off TMRCAs to 25, 50 & 100 years, depending on the estimated age range.

Ancestral Group 2

The St Clairs were documented in Caithness as early as 1321 when Sir Henry Sinclair of Roslin was the Scots baillie to Caithness; then in 1364 we find Thomas Sinclair similarly employed in Orkney where he was ‘Baillie of the King of Norway’. But it wasn’t until 1379, when the St Clairs of Roslin became earls of Orkney, that this geographic location really became associated with the name St Clair and Sinclair. What is interesting, is that the R-S5246 SNP has been given an estimated date very close to the time that the St Clairs of Roslin became earls of Orkney in 1379.

The single kit featuring under the main A2 Sinclairs of Orkney, Earldom group is very interesting. Their surname is Cummings and are positive for both S5246+ and FGC15253+, but negative for FGC15254-, so possibly quite early split after the foundation of the St Clairs of Orkney or just before when they were barons of Roslin in Lothian. 

A2i. The “Orkney and Shetland Cluster” is additionally positive for FGC15254+, FGC15256+ SNPs.

One of the kits in this cluster has their earliest known ancestor as born about 1600 in East Lothian. They don’t have any known ancestry much further north. If there were considerably more, then perhaps geographies for this cluster would expand further south; although it may only suggest a post Orkney migration.

A2ii. The “Caithness Cluster” differs, they are negative for the FGC15256- SNP, but are further identified by being positive for the FGC35613+ SNP.

Another interesting thing to observe is the DYS487 YSTR marker: A2i “Orkney and Shetland Cluster” is “13” and A2ii “Caithness Cluster” is “12”. Earlier matches are DYS487=13, so we could be looking at the “Caithness Cluster” mutating away on this marker.

The Z8 SNP Pack is the recommended option for those who match close on the YSTRs

Note: the kits marked S2O (Sinclair 2 Origins) are related to this group through their early - possibly Frankish - to pre-medieval Germanic origins. 

Resources:

FTDNA haplogroup projects, and geographical projects such as the FTDNA Orkney project

https://www.familytreedna.com/public/Orkney/default.aspx?section=yresults

If you are R1b-P312, search out your haplogroup in Alex Williamson's The Big Tree, which is a draft phylogeny for NGS (next generation sequencing) raw data from tests like the Big Y 

http://www.ytree.net

If you don't know where that SNP belongs, search for it in the NGS YFull Tree

https://www.yfull.com/tree/