Monday, May 19, 2014

Once Upon A Time: A SNP Fable

This SNP fable is not literally true in all regards. It is a "fictumentary" based on what we know but liberties are taken to fill in blanks where science has yet to provide more definitive answers. I hope that each time I tell it there will be less fabrication and more scientific fact. SNP discoveries are now being made so fast that such an expectation is not impossible.
SNPs are permanent changes in one location along the genomes of our ancestor that have been passed down to us. We can trace the accumulation of these SNPs, much as we could follow the paths of our ancestors backward in time as if they had left notches in tree trunks as they made their journey through time.

This journey can be traced back thousands of generations. However, in the interest of time, I will fast forward down to the last four millennium or so. This is the story of the journey of my own paternal line as I am discovering it with my results from the BIG Y test. 

As most of you have discovered, all families who share the same surname are not recently related. In my case we discovered a decade ago in early ySTR testing that the Dowells who flourished in Southern Maryland in the late 17th century were not biologically related to those who flourished in Central Virginia in the early 18th century. The surname came into use independently in more than one location. However, these two clans who were to become Dowells had traveled down the SNP highway from the beginning of time until they separated as they approached the Atlantic coast of Europe about four thousand years ago. They were both part of the great R1b migration out of Central and West Asia sometime after the last ice age receded. 

For those of you who know a little about SNPs, both of these two groups who became Dowells belonged to R-L21 which is the most prevalent haplogroup along the western coast of Europe. The timeline is still fuzzy but a few hundred years later they were both part of the SNP DF13 that was the major branch below L21. Here they came to a parting of the ways that we are just now beginning to be able to decipher with results from tests of discovery such as BIG Y, Chromo2, Full Genomes, etc. These tests are still not for the casual genetic genealogists or the timid of wallet, but they are where the fast and furious action is.

The trail of my own paternal line is being revealed to have branched off at SNP S1026. So far the Chromo2 project has discovered six individuals whose ancestors have passed this SNP down to them. Seven, including me, have been identified by the BIG Y test. And the number seems to grow weekly. 

So far my tale is more fact than fiction, but buckle your seat belts. The chart above is thought to describe the genetic journey of seven of us over the last 3,500 years or so. However, we don't know yet in what sequence each of us passed through these various SNP junctions. We will learn more about that as more members of this clan have test results.

The Fable

However, as of now it appears that each of us have approximately thirty or so SNPs spread out over a little more than three thousand years. That averages out to about one SNP junction every one hundred years. It appears at the moment that ancestors of the man whose path is second from the left never left France for the Isles. They stopped just short on the Brittany coast across from Cornwall. The ancestors of the rest of us appear to have made the plunge at some point in the last three thousand years or so. The ancestors of the man on the left seem to have made it to Ireland. 

The ancestral lines of the five of us on the right seem to have stayed together for another five hundred years or so. We all share 5 SNPs not shared by the two on the left. 

Have you heard the one about the three brothers? It looks as if something like that happened almost 2,500 years ago. One headed for Scotland. Well, you
have heard that one before. 

My own ancestral line [the middle one in the chart above] and that of another fellow traveler continued together for about seventeen hundred years or so. The two of us already had STR matches but no common paper trail for the last three hundred years. According to my fable version of our common family history, our closest common male ancestor might have been as far back as eight hundred years ago. TiP at FTDNA predicts our connection is a little closer:  
Generations  Percentage
8 11.54%
12 60.70%
16 88.49%
20 97.48%
24 99.55%

Oh well.

I look forward to the opportunity to learn more about the journey of my own accumulation of SNPs. If you can correct what I have written or add to it, I would love to hear from you. That is how I learn.

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