The number of ancestors is simple to calculate as it is a simple mathematical progression: every person has two parents, four grandparents, eight great-grandparents, sixteen great-great-grandparents and so on. The number doubles with each generation. As you go back in years, the numbers soon become very large.

Family Forest, the producers of a CD-ROM lineage-linked database that digitally connects people with each other, can be considered experts in this topic. They have an excellent chart that illustrates the numbers quite well. Take a look at: www.familyforest.com/resources.html

Answer to the earlier question: If we assume that there is a new generation every twenty-five years, someone born 400 years before you would be 16 generations removed from you. According to the Family Forest chart, you would have 65,535 unique ancestors born in the previous 16 generations, assuming no overlap (that is, none of your ancestors were cousins to other ancestors).

However, all families can find a few cousins somewhere in the limbs of the family tree, resulting in the same ancestor(s) showing up in multiple places in the pedigree charts. Ask anyone who has done French-Canadian genealogy or has researched any families that lived for generations in one small village almost anyplace on earth.

If you go back to the time of Charlemagne, roughly 40 to 50 generations ago, you discover that you theoretically have more than one trillion ancestors! Of course, that’s far more than the total number of people who ever lived on the face of the earth. Obviously, you and everyone else have cousin marriages in your ancestry, resulting in ancestors showing up in multiple places in your family tree.