Logan DNA Project, Part 1

Introducing Y-DNA testing

“Brick Walls” are the inevitable dead ends in every branch on every family tree. We all have them, but thanks to the Logan DNA project, we can look beyond them. For example, many members of the project now know where in Scotland their Logan ancestors lived. This includes differentiating between Highland and Lowland Logans.

The purpose of this article is to introduce you to genetic genealogy with a focus on the Y-DNA test and the Logan DNA project. Let’s start by briefly looking at the three major tests that are available commercially today:

Autosomal DNA is the most common test. It is offered by 23andMe and Ancestry. This test looks at the DNA you inherited from both parents and compares it to other test takers. The amount two test takers have in common will tell them how they are related. This test is very powerful for identifying relatives. However, over time the amount of shared DNA drops rapidly, and, therefore, this test will struggle to find matches beyond a 4^th cousin. This limits how far back in time this test can be of assistance.

Mitochondrial DNA (mtDNA) is inherited exclusively from your mother. Unlike Autosomal DNA, the mtDNA is passed down from a mother to her children without any mixing. This means that you are likely to have an exact copy of your mother’s mtDNA.

 This test compares your mtDNA to other test takers, with the focus of grouping those with like DNA together into “haplogroups.” Due to mtDNA’s very slow mutation rate, you and your exact match may share a common ancestor who was born thousands of years ago. As a result, testers can expect to receive a migration map showing how their maternal line moved throughout the world over time.

Y-DNA, like mtDNA, is passed down without mixing. Unlike mtDNA, Y-DNA is only passed from father to son. Therefore, this test is ideal for surname studies, like the Logan DNA project. Projects like these allow testers to look beyond their brick wall and find dates and locations of common ancestors.

Inheriting Y-DNA:

When you participate in a surname project, it is critical to identify who can take this test. To assist, please refer to the Y-DNA descent tree in figure 1. This tree illustrates how Y-DNA is passed down from a fictional John Logan. In this tree, you will see that all boxes in green represent males who inherited John Logan’s Y-DNA. The red boxes did not. Therefore, only sons B & C inherited John’s Y-DNA and could directly participate in the Logan DNA project.

Figure 1- Y-DNA descent tree

Testing Y-DNA:

Y-DNA is passed on from father to son directly, without mixing, and typically unchanged. However, on approximately every 3-4 generations mutation occurs (changes to the DNA structure). If this mutation does not impact health, it will continue to be passed down the paternal line. It is these mutations that Y-DNA testing uncovers.

As mutations to Y-DNA happen at a predictable rate, scientists can estimate the birth year for tester’s ancestors, along their paternal line. At the risk of oversimplifying, if two testers have a very small difference between their Y-DNA, then they are likely to have a common ancestor that lived within the last ~ 200 years. Major differences in their Y-DNA could mean they share a common male ancestor who was born ten thousand to hundreds of thousands of years ago.

Testing companies represent this by putting people into “haplogroups”. For example, most, and maybe all, individuals in green, in figure 1, would be in the same haplogroup.

Haplogroup descent tree (Haplotree):

Not only can testing companies tell you what haplogroup you are in, they can tell you how haplogroups relate to each other. This allows testing companies to place their customers on their Y-DNA haplogroup tree.

In figure 2 the same fictional John Logan from fig. 1, has passed his Y-DNA down 5 generations to two 3^rd great-grandsons. At some point between John and 3^rd great-grandson C, there was a mutation in John’s Y-DNA. A test would be able to identify this mutation and recognize that 3^rd great-grandson C is part of a haplogroup that descended from John’s. As there have been no mutations between John and 3^rd great-grandson B, they are both in the same haplogroup.

Figure 2- Simple haplogroup tree

If you run this simple example over a 200k – 300k year time span, then you get a haplogroup tree for all men. As things stand today, the testing company we use for the Logan DNA project has identified over 93,000 branches in the Y-DNA haplotree, allowing for a detailed family tree for all men.

To visualize this, figure 3 illustrates a very simplified version of the Y-DNA haplotree. To keep it manageable, it focuses on “super haplogroups”, which represents very large populations, haplogroups combine to make up a super haplogroup.

As you can see in figure 3 our earliest ancestor was the “founder” of super haplogroup “A”. His descendants were the first men in super haplogroups “B” and “CF”. This continued for thousands of years until all current super haplogroups were formed. One of the more recent ones was super haplogroup “R” which emerged around 26,000 BCE, give or take ~4,000 years. Most men of Scottish descent have inherited their Y-DNA from that first man who formed super haplogroup “R.”

Figure 3 - Y-DNA descent tree

Beyond this chart all super haplogroups continued to diversify. As there are not enough letters to represent all the haplogroups, the names had to get more complex. One example shown in Figure 3 is haplogroup R-M173 which descended from super haplogroup R.

The Y-DNA haplotree will do much more than tell you where you sit within this alphabet soup. For example, your author’s haplogroup emerged from super haplogroup “R.” Our Society’s President, J Kevin Logan emerged from super haplogroup “I”. These two connect at super haplogroup “IJK” which emerged from “GHIJK around 45,000 years ago, give or take 6,000 years. In other words, both Kevin and I share a common male ancestor who lived ~45,000 years ago. Current research suggests that this common ancestor may have lived on the Arabian Peninsula with his descendants taking diverse paths to the British Isles.

In my next blog I will discuss how you can join the Logan DNA project, how to take the test, and expected outcomes.