Curiosity got me on that too, so I looked for info and found Human Y-chromosome DNA haplogroup which indicates that "Y-chromosomal Adam is the name given by researchers to a theoretical male who is the most recent common patrilineal (male-lineage) ancestor of all living humans." There's a chart lower down showing the dispersion.
Thanks, Boogieman - interesting.
Here’s a creationist’s take on the haplogroups and Mt DNA as viewed from a Biblical perspective:
http://creation.com/noah-and-genetics