Engines of Our Ingenuity

No. 389:    COBA

by John H. Lienhard

Click here for audio of Episode 389.

Today, we watch a lonely city die. 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.

The 7th-century Mayans didn't have the wheel. They didn't have anything like the mathematics that was already old in Europe and Asia. And yet, during the next century, they built the city of Coba in northeastern Yucatán. The city covered 30 square miles and was home for some 50,000 people. Until recent centuries, that was the size of the great cities of Europe -- Athens, Rome, Paris, and London.

The crowning glory of Coba is a 120-foot pyramid rising out of the undergrowth. From its top you can see 6500 mounds where the jungle has grown over its buildings and buried them.

Another kind of structure catches our eye when we look more closely. Fifty roads radiate from the city. Actually, road is an odd word to use in a land that never took up the wheel. These are stone footpaths that reach as far as 60 miles through flat jungle and swamp terrain. They express linkage and connection for a highly civilized people more than they express real need. Along these roads we find ceremonial stones engraved to great people and events. We also find toll booths.

Coba lasted 600 years. Finally, its people walked away and let the jungle grow over it. They left 300 years before the Spanish invasions. They weren't driven out; so what did happen?

The answer is that this great city wasn't the fruit of great technology. It was instead a tribute to organization and cooperation. The Mayans of Coba were isolated from other advanced peoples. They used what they themselves invented; but other cultures didn't feed them with ideas. Without the wheel, they didn't have pulleys -- no block and tackle. They used less technology than the Egyptians 4000 years before them. They made majestic structures without the keystone -- without geometry.

The lack of one technology in particular killed Coba. The Mayans didn't know about crop rotation. Agriculture was first invented in the Middle East -- in a much harsher land. Those first farmers learned to nurture the soil that nurtured them. But the Mayans planted corn, over and over, on a shallow bed of topsoil. In the end they killed the earth. They drove themselves away.

The people of Coba did show us inventive genius. We find traces in this abandoned city -- the idea of an alphabet, of sewage disposal and plumbing, of art, and of fish farming. What they lacked was cultural mixing. They lacked an infusion of ideas from other peoples and other lands. ¨What really killed the city of Coba? It was the lack of alien influence -- the strangers from across the river -- people with different thoughts. Coba died of intellectual isolation.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)


Barr, V., A Mayan Engineering Legacy, Coba. Mechanical Engineering, Vol. 112, No. 2, 1990, pp. 66-71.

Barr's article was based on material provided by Glenn Barr, Santa Barbara Community College, and by Dr. Brian Dillon, UCLA.


The Engines of Our Ingenuity is Copyright © 1988-1997 by John H. Lienhard.

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