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Second Founder Theory

by Philip Shaddock

I was puzzled for a long time about the fact all the branches of the Shattocke family seemed to have sprung into existence in the early to mid-15th century whereas the YFull estimate of the most recent common ancestor was dated in the early 14th century, a century earlier. Why did it take a century or more for the branches from that male founder to appear? It wasn't until I began looking at lists of SNPs returned by advanced YDNA testing that I came up with the reason why.

The studies of our ancient family branching is based on examining a type of mutation found on the male Y chromosome called an SNP (single nucleotide polymorphism). These mutations occur, on average, once every 144 years (using the Family Tree DNA "Big Y" NGS technology). 

In the diagram at the left, the long row of yellow dots represents a list of SNP mutations found in all Shattocke descendants, including our Parrish and Byars cousins. The mutant SNPs we share came into existence over a 2300 year period. In fact the closest living relatives to Shattockes who have tested share with us a man who lived 4300 years ago with a mutant SNP called Z36. About 1315 AD, a descendant of Z36 had an SNP mutation called "Y16884." In their analysis, YFull identifies Y16884 as the common ancestor of us all. But was he the real founder of our family?

The 37 SNPs that show up in all Shattocke and Parrish / Byars Big Y DNA results are not the only ones we have. They are just the mutant ones we share.

As the family branched, new mutant SNP appeared. In the diagram C and D sub-branches of the family share the SNPs that are colored green. Groups A and B do not share these SNPs because they occurred in descendants from a different branch of the family. 

The A (blue), B (red), C (pink) and D (orange) sub-groups have what are called "private SNPs" meaning they have SNPs that are not shared by the other branches of the family. The basic logic behind the diagram is that mutant SNPs are inherited by sons and passed on to ensuing generations. That long yellow sequence of dots means that our branch of the human family accumulated 37 private SNPs over the 2300 years since we split off from the Z36 male common ancestor. No other humans except Shattockes and our Parrish and Byars cousins has this unique combination of mutations. 

Note: The diagram is an illustration for this thought exercise, not a reflection of actual Shattocke data, except for the symbolic representation (the 32 yellow dots) showing shared SNPs found in every Shattocke's result.

Because SNP mutations only occur every 144 years on average, there is not going to be an SNP mutation in each generation.  The empty circles with dotted lines represent a generation in which no SNP mutation occurred. (The other possibility is that the DNA test failed to detect an SNP or we have not tested an individual with this SNP as yet.)

What you see in the diagram is a scenario where a second founder of the Shattocke family was born without an SNP mutation. So he is invisible to the advanced YDNA test.  He is not actually a second founder. He is in fact the founder, the real common ancestor of us all. Because he did not have a new SNP mutation he is invisible to DNA testing!

He was born around 1420, although this date cannot be precisely pinpointed because he left no signature on the SNP trail. I have given him this approximate date because records show Shattockes existed in Somerset and in Devon near the border with Somerset as early as 1525. There is also a record of a Thomas Shattocke, who was a tenant in the Taunton Deane area of west Somerset dated 1450.  

At this point the oldest branch of the Shattocke family are the North Molton Shattockes with an estimated common ancestor who lived in 1465. Because SNP mutations are random, we have to treat these dates with some skepticism. However the more Shattocke descendants we DNA test the more confident we can be about the accuracy of the dates. 

What gives me confidence about a theory of a second founder, in fact the real founder of all Shattockes and Parrishs / Byars, is the observation that no common ancestor has been found earlier than 1465. The genealogical data drawn from records like wills, tax records and protestation forms also indicate a very small population of Shattockes in the early 15th century.  

The best theory to fit the data is that we are descended from a common ancestor who lived sometime in the 15th century. He had no SNP mutation so we will not find an SNP for him in our results, but we can extrapolate his existence from the data. I am calling this the "second founder thesis," although he is the real founder, it's just that we cannot see him because he never had an SNP mutation.

But there is a big question that remains. I am saying the real founder lived about 1450. Shouldn't he have had cousins descended from Y16884 five or six generations earlier? 

In single surname studies, there is a natural attrition of the branches of the family tree over time. A family has all daughters. Sons have no children. Disease and death wipe out entire families. During medieval times population growth was flat due to these factors. Late in the fifteen century and in the sixteenth century, England's population growth recovered...in fact boomed. Study of the Shattocke genetic heritage parallels this pattern. So a possible theory is that only one of the male descendants of the original founding Shattocke (Y16884 in ca. 1315) survived the late medieval period. As the general population revived, six branches formed, descended from the "second founder," who lived sometime around the middle of the 15th century. 

That is one theory. There is a simpler theory.

I had assumed for a long time that Y16884 was a German immigrant who arrived in England around 1315. But what if that German immigrant arrived in England in the early 15th century rather than a hundred years earlier? That would explain why we have not found cousins descended from Y16884 anywhere in England or the former English colonies. If cousins of Y16884 do exist, they will be found in Germany, the Netherlands, Belgium or northern France and NOT England or its former colonies. And that would explain why the branches seem to blossom from a single individual in 1450 instead of 1315.

This solution takes care of another problem. Five of the six branches of Shattockes share variations of the the Shattocke name (Shattock, Shaddick, Shaddock, Shattuck, Shadduck). One branch has the name Parrish or Byars, but it was probably a Shattocke NPE in early 17th century Virginia. Etymologists have traditionally treated Shattock or Shaddock as a German name. Since surnames arose quite late in the medieval period, it is more likely there was a German immigrant to England with the surname Shattock ca. 1450 than ca. 1315. 

I am going to give the "second founder" the name of "Thomas Shattocke," the name of the tenant in the Taunton Deane list of 1450, and assume he was thirty years of age when the list was made.