On this subject, I found this article from our newspaper's Sunday supplement
rather thought-provoking.  It is a column by Marilyn von Savant, who is
listed in the "Guinness Book of World Records" Hall of Fame for "Highest
IQ."

Q: If we have two parents, four grandparents, eight great-grandparents and
so on, by the 30th generation a person would have 1,073,741,824
great-great...grandparents. How can this be explained? The population of the
whole world would not have been over a billion people in the day of Lady
Godiva, who was my husband's 28th great grandmother. (submitted by Julie
Tomlinson, Waycross, GA).

A: I answered this question once, but it has become so popular again that I
think we should revisit it. The number of 30th-generation ancestral
positions seems too large, as you say, but many people are occupying more
than one of those positions at the same time. Here's a diagram that
illustrates why, starting with eight children:

(this is followed by a rather long and tedious chart that essentially says:
1. Eight children when grown pair off into four couples.
2. The four couples produce the eight children.
3. Those eight children, when grown, decide to pair off in different
couples.
4. And these four couples produce eight more children.
5. When grown, these eight pair off into four different couples again, etc.
and so on.)

In other words, you have 16 fourth-generation ancestral positions, but the
same original eight people are fitting all of them. If your husband traces
his ancestry just past Lady Godiva, all those 1,073,741,824 roles you
mention would be filled (repeatedly) by the relevant portion (but not all of
them, as in Savant's special case) of the 300 million or so people alive
back then. Imagine: In the 11th century, your husband could have called Lady
Godiva "Grandma"!

This gave me an insight into evolution I had not considered before.  When
you think about it, you wonder why more living things are not alike instead
of different.  I.e., we all descend from some common ancestors.

Just think, we may all be related one way or another (what horrible thoughts
that brings up!).

Sylvia S. Edwards
Huntsville, Alabama
[log in to unmask]