What is a Y-DNA haplogroup?
A Y-DNA haplogroup is a group of individuals who share a common ancestor through the direct paternal line. They are distinguished from each other by the presence of certain mutations on the Y-chromosome of male members of the group. For the haplogroup to be widespread, the common ancestor had to have lived thousands or tens of thousands of years ago. Haplogroups are useful in two ways. One way is that it tells you something about your ancestry. If you join the National Genographic Project or read books on the subject, you can learn when and by what route your ancestors left Africa and something about the path they took to wherever they ended up. Because some haplogroups are correlated with certain places, you can sometimes learn something about their ancestry. For example, the I1 haplogroup is associated with Scandinavia and Northern Germany and certain sub-groups of R1b are associated with Ireland, Frisia, and other parts of Europe. A second way in which haplogroups are useful is to t
