Todd A. Farmerie (taf2@po.CWRU.Edu)
17 Jan 1995 02:08:21 GMT

In a previous article, () says:

>How can we possibly have more ancestors in a coexisting generation than
>the total known population of the earth?
>I know for a fact that I have a mother and a father who each has a mother
>and a father, etc... The direct ancestral chart would look like so:
>Generation Population
>1 2 (Mother and father)
>2 4 (grandparents)
>3 8 (greatgrandparents)....
>20 1,048,576
>30 1,073,741,841
>Going backwards it does not take too long to run into a problem.
>What am I missing? Please email your response to me. Thanks

This is nothing new to genealogist. Prior to recent times, people lived
in small towns with little mixing. Even with forty families in this small
town, it would not take long for all residents of the town to be descended
from all forty of the original families. Taking your calculations in
reverse, a potential spouse would be descended from:

Generation # of founding families descended from:
1 1 (parents)
2 2 (mother's & father's)
3 4 (each grandparent)
4 8
5 16
6 32

I will stop here because after only 6 generations (ca. 180 years) a
potential bride is descended from over half of the original families. The
groom is also descended from the same number, and thus every bride and
groom will both be descended from (assuming no prior intermarriage) 24 of
the founding couples, and each only have 8 unique to them. Take this
another three generations, and every potential partner is descended from
every one of the founding families. After this point, not a single new
ancestor is added with each successive generation. (Many New England towns
were approaching the point where there were few unrelated brides by the
time of the American Revolution.)

Each immigrant to the community carried new ancestors, but these likely
came from the adjacent town, and descended from all of the families there.
Thus, after the spread of that blood through the new town, a second
immigrant from that town would add nothing. In addition, with an expanding
population, the neighboring town probably descends from the same founder
population as the founders of the town in question did.

When this pattern is viewed over a millenium (or more) that passed between
major population movevents, it leaves everyone within a large area
descended from a small number of founders 30 generations before, with few
additional ancestors added from the time of that starting point, even when
marrying someone from the next county or region.

This discussion, of course, focusses on European models, but in other parts
of the world, different marriage patterns (such as always getting a bride
from a neighboring community) result in the same effect over 30
generations, that being no new ancestors with additional generations.

As you can see, this is nothing that cannot easily be explained, nothing to
be sceptical about and nothing that has any bearing on some of the other
groups that this is cross posted to. Whatever your point was, there is
nothing amiss here.