Today, we ask why the Aztecs didn't make full use of
metal. 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.
One question that torments
historians of technology is the "Why didn't?"
question. Why didn't the Chinese, with all their
inventions, produce the industrial revolution? Why
didn't the Romans ever make full use of water
wheels? Why was Europe 400 years behind China in
printing with movable type? All those questions
come back upon the present, of course. Why aren't
we doing the right thing today -- whatever that
So: why didn't the Aztecs ever emerge from the
stone age? Why did such a remarkably advanced
people make such limited use of metal?
Anthropologist Terry Stocker offers a troubling
answer. When you already have a fine technology,
you don't see beyond it. And the Aztecs had
obsidian for their axes and knives.
Obsidian is a naturally-occurring glass, usually
black and opaque. It's harder than steel, and it
fractures smoothly. By splitting it, you can create
murderously sharp blades. For the early Greeks and
Egyptians, obsidian was a profitable medium of
trade, not so easily available. Once artisans had
shaped cutting tools from bronze, they had reason
to give up obsidian.
That never happened in the Aztec world. Southern
Mexico was richly endowed with obsidian.
Anthropologists now think the huge and mysterious
pre-Aztec city of Teotihuacan, near Mexico City,
was the center of an obsidian industry.
Aztec swords were made with rows of small obsidian
teeth. They were murderous weapons for cutting an
enemy. For a long time, historians have marveled at
the amount of ceremonial self-mutilation the Aztecs
underwent. Now we find that being cut with obsidian
is less painful than you'd think, because it makes
such a sharp edge.
So obsidian became woven into Aztec worship as well
as Aztec function. What need could there be for a
replacement material? The Aztecs didn't develop
their use of metal because they couldn't see beyond
Then the Spanish came with their steel guns,
swords, and cannon. They conquered the Aztecs and
tried to erase their history. The sublime irony of
that is, we now use Aztec obsidian to reconstruct
that history. For obsidian carries the imprint of
its own past. Once fractured, obsidian slowly
reacts to water in a chemical process called
hydration. It's possible to read the age of
artifacts by seeing how far that process has gone.
I have a little Aztec image on my desk. It's smooth
and inky black, carved from Mexican obsidian. It
catches the light and rewards the touch. It tells
me, as surely as history does, why the Aztecs
continued to write their story in this hard,
hypnotic, even magical stuff, when simple reason
would've preferred gray steel.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds