Today, you and I are kin. The University of
Houston's College of Engineering presents this
series about the machines that make our
civilization run, and the people whose ingenuity
created them.
A while back a friend got
deeply into genealogy. One day he pulled out some
papers that showed he was related to Charlemagne. I
allowed that was very impressive. Now I've just
read an article in the magazine The
Sciences, and guess what! I am also kin to
Charlemagne. And so are you.
Each generation back, the number of your great
grandparents doubles. The length of a generation
can be variable. For most cultures, thirty years
would be a conservatively long generation.
Charlemagne lived in the late eighth century, about
forty generations ago. To count how many
progenitors you had in the late eighth century we
raise two to the fortieth power. That gives about a
trillion. The problem is, that's at least a
thousand times more than the world population was
in AD 800.
"How can that be?" you ask. Easy enough.
Charlemagne was almost certainly your grand-parent
many times over. Subsequent generations were almost
all cousins, albeit many times removed.
Now, while you can safely bet that you're related
to Charlemagne, there remains a very slim chance
that you're not. So let's go back further.
Cleopatra lived some 67 generations back. The
number of your grand-parents that long ago was many
trillion times larger than the population of Earth.
Follow your maternal grandfather's lineage, and
your paternal grandmother's, and you'll soon enough
run across increasing numbers of the same people --
like Charlemagne -- as you move backward in time.
Now go all the way back to early modern humans,
30,000 years ago when Earth's population was very
sparse. The number of your forebears is so vast as
to be beyond my calculator's ability to show it to
me. Each of those ancient beings had to've been
your grandparent an uncountable number of times
over. We needn't go anywhere near that far back to
be certain of our relationship to Confucius,
Alexander the great or King Tut. Every Viking woman
and medieval African chieftain, every early Mongol
mother and Australian bushman would turn up over
and over in your family tree.
When we've finished this exercise, racism becomes
no more than a bad joke. The idea that I am not
black, and that Marian Anderson was not white,
becomes ridiculous. After not-too-many centuries,
we all share the same forebears. Actually, it'd be
more accurate to say that the concept of race
itself is the bad joke.
The genetic implications are vast. We're a single
species with far less genetic diversity than we'd
assumed. As the number of our progenitors fans
outward into the past, and the actual population
shrinks, we reach Africa some 4000 generations ago.
The number of the first modern humans appears to've
been only a few thousand.
We thus come quite close to being the children of
an ancient Eve and Adam. Our vast uncountable army
of forebears all converge upon that small band of
early human ancestors who spread out, first across
Europe and Asia, and then over the entire world.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
(Theme music)
