Genealogical Y-DNA tests claim to be specific to male bloodline and able to determine relation between two people. How then can two known cousins both in male lines documented in written sources have a genetic distance of one at twelve markers ? In a family traced reliably through charters and manuscripts back to the 1100's, where surname changes have been thoroughly traced, how can it be that DNA samples from hundreds of other surnames who have no known connection or alliance to this family in nearly 1,000 years of its history be DNA matches in a hereditary male line ?
Could it be these tests are not accurate or can be maternally influenced, or maybe even designed to be misleading to keep people coming back and paying for more tests ? How would you even know ? An expert in DNA studies at John Hopkins University I spoke with said the further back in time the greater chance for variances in DNA and it is possible for two people with a genetic distance of even 3 or 4 to still be related just further back in time. How reliable then does that make these tests ? Certainly instructing people the results much be a direct match for two people to be related is misleading.
The above anomalies cannot yet be explained and the award goes to those who can take two different surnames with matching DNA and prove through written sources where that division occurred in a common ancestor.