After testing a small number of Sinclair / St. Clair / Sinceler (etc) family members worldwide, we noticed that we had several haplogroups present in our study who didn’t seem to share a common ancestor until quite far back in time, some as long ago as 30,000 BCE. This led to many in our family voicing the oft-repeated thought that there was only one ‘true Sinclair bloodline’ and the others were the result of non-paternity events or folks in old Scotland taking the name of the laird. This notion is, in my opinion, the direct result of genealogists who seek to find one ancestor back in time for every member of the family who shares a name. Our Sinclair family is no different. The one supposed ancestor for our family has, for the last 200 years, been ‘documented’ as Rollo of Normandy. I suspected that the answer was not quite so clear cut as this and began looking for alternative hypotheses.


Our hypothesis is that, ours’ being a name adopted from land in western Europe, some of our ancestors with wildly differing haplotypes might have found themselves living on the land in the period in which surnames were being adopted. If correct for even two of our lineages, this study will prove that our family origins are far more complex than traditional documents genealogy can resolve.

Alternatively, if the data leads to the likelihood that a significant number of the family were not in regions from which they could have acquired the surname during a reasonable period in which surnames were acquired, then they must have taken one of the Sinclair variant names from some other source, leaving open the previously mentioned “laird” theory and others.

The General Process

Men: DNA results are a string of 37, 67, or 111 parts of the human chromosome called alleles. Each test subject is checked on the same parts of the chromosome. The values will be different based on how they’ve mutated over the centuries. Cousins who share a male ancestor within a genealogical time frame will find they’ve only mutated on a few of these markers. However, in some of our lineages, the alleles have mutated more rapidly, making it look like they’re not as closely related. Family Tree DNA’s comparison tools cut it off at 7 steps of mutation.

Men who stop with the 37-marker or 67-marker test are missing out on deeper learning. An example is the old televisions which had a fuzzy picture. That’s the 37 and 67-marker tests…fuzzy. The Big Y 700 test is like a huge 4K TV. You will be looking at the same picture, but it’s super clear what you’ll be looking at.

Women: Genetic females cannot take a Y-DNA test because they do not have a Y chromosome. However, if you are interested in learning about your paternal line’s ancestry, we recommend finding a genetic male to test—like a brother, uncle, father, or cousin. Another thing you can do FTDNA’s Maternal Ancestry test for $159 USD and look for cousins who might be Saint-Clairs further back.

These sequences of alleles are not found within genes and have no known genetic function. The reason it works for genealogical purposes is that the observed mutations, once they happen in an individual, are carried by that person’s descendants forward in time and are like road signs along the way. The mutating alleles are neither harmful nor helpful; they simply happen now and then, and they persist because the body doesn’t notice the difference. These persistent yet changeable variations are the markers that allow us to tell our lineages within a family apart and roughly how far apart they may be.

FTDNA also tells each person tested which haplotype they are. In population genetics, individual haplotypes are classified into wide categories called haplogroups. Haplogroups are so broad that they are of little direct value in genealogy. Think of them as the big branches on the tree of human evolution.

When compared to good documents research, or other data points, the alleles become much more meaningful. We currently have 14+ lineages which seem to connect sometime within the last 5,000 to 20,000 years. This is not uncommon. I’ve looked into many different family projects and many of their lineages don’t appear to connect until at least 25,000 years ago. Some don’t connect for well over 70,000 years. Our family is lucky in that we have tremendous documents research back to circa 1000 AD which gives us another data point with which to compare.

When you take the test, the results come back to both you. They will also come to Steve and Danny. At that point we will begin to help you interpret what they mean.

STRs versus SNPs

STRs (Short Tandem Repeats) can mutate at any time. When I started the DNA study back in 2004, all we had to test were STRs…I think only the 12-marker and 25-market. Family Tree DNA kept adding more STRs until they got out to the 37, 67, and 111-marker tests. The 111-marker test helped  understand things.

SNPs (single-nucleotide polymorphisms), are believed to mutate only once and then never again, making them incredibly reliable for determining relatedness.

Our Herdmanston Lineage is a good example of why SNP testing (pronounced “Snip”) is so critical. When we tested a direct male blood descendant of the this line and his STR results began coming in, he matched a group of about 10 people in the study in the 12-marker region. This is a group I had nicknamed “The Mystery Lineage” because, while we knew they all had genealogy pointing back to lowland Scotland, we couldn’t pin them to the family narrative.

The problem was, he didn’t match them on the 25-marker region, so I waited on the 37-marker results to come in. Again, he was matching no one at all in the entire FTDNA database. Finally, when the 67-marker results came in, we had matches, the closest being a 62 of 67-marker match. But these markers aren’t very reliable when you’re looking for connections before the 1700s, or to definitively prove matches from the 1700s to today. When we got several intrepid DNA explorers in the Herdmanston lineage to do the Big Y test (pre-Big Y 700), what I had been calling the mystery lineage all fit neatly into the Herdmanston bunch. Another group who goes back to Virginia also folded into the Herdmanston group.

That’s why we recommend that males in the study take the Big Y 700 test. It will test out to more than 700,000 parts of the human chromosome.

This is a sample of our extensive results page, which helps our study participants understand how to learn more after advancing from STR testing results to SNP testing (the full chart is online here).