Introduction to Y-DNA

When a man and a woman have a child, their DNA is randomly shuffled and passed down to the off-spring, with only pieces mimicking either parent. In this way precise genetic information about our ancient forebears going back over a couple of centuries becomes lost and is difficult to reconstruct due to this shuffling. Fortunately there does exist a small piece of DNA, which remains largely unchanged from generation to generation. It is the Y chromosome, a tiny fraction of our genome which has the sole purpose of being the sex determinator in males. This is passed down from father to son, generation after generation and remains largely unchanged aside from small mutations which can be used to measure relatedness of males and construct phylogenetic trees of their common paternal ancestry.

This is exactly analogous to surnames and also to the tribal and the patrillineal nature of Gaelic Irish society (and all Indo-European cultures). In this way it acts as an immutable genetic surname (or pre-surname tribal marker). So, you may realize that modern science can be combined with ancient genealogy (or modern genealogy for that matter) to test their validity. The essence of this is if a large group of carriers of a surname possess a single Y SNP mutation, then we can associate this mutation with their most recent male-line ancestor (may or may not be the founder of the surname itself). If we have two males with different surnames, but that, according to ancient genealogies, converge on a common dynastic founder in, say, the 5th century AD, and they share a common Y SNP mutation, then it can also be tenuously construed that this mutation is associated with this common ancestor. This combination of modern scientific developments with ancient genealogies is the essence of this project.