Our local Genealogy Society booklet notes that a test is available to anyone with 150 pounds (English) to spare. It is based on the Y chromosome, which traces male lineage.
Y chromosomes are passed down the male line almost completely unchanged, a man's Y chromosome being 99.9% the same as his father's.
There are mutations but the average rate is only one change in 500 generations (4 generations per century = 12,500yrs).
This means that men with a male ancestor in common will have nearly identical Y chromosomes.It also means that the mutation rate (? each 12,500yrs) can be used to determine when two men last shared a common ancestor.
Would this mean that as the Adair lineage basically seems to have emerged about AD1450 that all male Adairs may have the same DNA back 500 generations or 12,500yrs if there were about 4 generations each century ?(My arithmetic is not 100%)
Would it be the father-son difference is 0.1% each (male) prove anything relative to other Adairs ?