In order to be born, you needed:
2 parents
4 grandparents
8 great-grandparents
16 second great-grandparents
32 third great-grandparents
64 fourth great-grandparents
128 fifth great-grandparents
256 s...
In Tasmania and Kentucky they skimp a bit, I'm told, and some don't have the regulation number of great-grandparents :D