While genealogy has been studied for centuries, an important modern tool is DNA. By comparing DNA tests, we can find how our families are connected. For a surname study, the most important type of DNA test is called “YDNA”. The Y Chromosome is unique in that it is ONLY carried by males and is passed on essentially intact from father to son through the generations. Since, in many cultures, the Surname is ALSO passed from father to son, we can use matching YDNA tests to identify whether two or more men have a common male ancestor.