Today, we wonder why we don't have wheels. 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.
So! Wheels are so great: why
don't I have wheels? Why do I have legs? Animals
move by creeping, leaping, walking, running,
slithering, swimming, and flying. Some animals, and
plants too, even move by rolling. But never on
wheels. Why no wheels?
Once we found out how to make wheels, we went
rolling off into the sunset with them. We took
their use further and further into our lives. We
made carts and chariots -- then potter's wheels,
spinning wheels, gears, and water wheels. We made
clockwork. We made machinery. Finally we made the
automobile.
Our traveling machines roll, but they hardly ever
walk. We've experimented with walking machines, but
we haven't managed to make one that works. Wheels
are the means of choice for moving about. Yet, if
they're so fine, why has natural selection never
fitted any living thing with wheels?
Stephen Jay Gould raises these questions. He points
out that at one time wheels entered human history
and then disappeared. Imperial chariots ranged
North Africa and the Middle East for 2000 years.
But when the Romans finally left, so did chariots.
Wheels were almost forgotten until modern times.
Camels took up the burden of transportation. They
needed less manpower. One boy could handle six
camels; but it took a drayer and several thirsty
oxen to pull a cart. The camel was better suited to
everyday needs in the arid lands. Wheels didn't
fully return to the desert until there were engines
to turn them.
When we look closer we find that the mechanics of
legs and wings are so superbly complex that our
technology simply hasn't mastered them. Maybe
wheels are just a simple stopgap we've had to use
because we can't design legs.
Maybe! But if we can't design legs, neither has
nature ever made a wheel. A wheel poses what we
call a topological problem. It cannot be attached
to the axle about which it turns. It cannot share
the blood supply or be controlled by its owner's
nervous system. The best nature has done is to
equip certain stomach bacteria with a kind of
propeller. That propeller, or flagellum, as it's
called, is so small it can take nourishment, and
neural control, through its cell walls. That's out
of the question for larger organisms.
Of course, nature has bred the wheel. Nature has
bred the one animal clever enough to invent the
wheel. Someday we'll master the wing and the leg as
well. Only when we've learned to make both legs and
wheels will we be able to talk about the
superiority of one over the other.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
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