SCOTT SIMON, HOST:
Just like today, ancient cities needed sources of clean water to flourish. Obviously, there weren't any Brita filters around when the Mayans lived some 2,000 years ago, when BJ Leiderman began to write our theme music. But new excavations in Guatemala show that Mayans developed a sophisticated method to clean their drinking water, which is used in filtration systems today. Archaeologist and botanist David Lentz is director of this project and professor at the University of Cincinnati. Thanks for being with us.
DAVID LENTZ: My pleasure to be here.
SIMON: What did you find?
LENTZ: Well, Tikal was one of the great ancient Mayan cities. Some people call it the capital of the ancient Maya realm. And at Tikal, there are no rivers or lakes or any permanent bodies of water nearby. The Maya, to actually develop the city and be able to sustain a city, they had a whole ring of reservoirs surrounding the city. In the city, they had many large plazas, and these were all paved so that they would run into the reservoirs. One of the reservoirs - Corriental, it's called - had a zeolite and sand filter at one end. And as water came down into the reservoir, it went through these filters first before dropping into the reservoir.
What's unique about the sand and the zeolite is there's no sand or zeolite around Tikal, so the Maya had to bring this in. And there's a source about 30 miles away that they could've brought this sand and zeolite.
SIMON: How did they figure this out?
LENTZ: You know, the Maya were a very clever and inventive people. They had stunning architecture. They had beautiful sculptures. They were adept at astronomy. They had mathematics.
SIMON: Unfortunately, Tikal, this glory of the ancient world, collapsed, disappeared about a thousand years ago. Some scientists suspected for years that maybe the water reservoirs and water supply failed them.
LENTZ: One of the things that we found - that many of the reservoirs were contaminated with mercury. What happened with these filters is that they would build these filters, and then tropical storms would come along, and then they would wash them out. And then only after they didn't replace the filter do we find mercury. And this came from this material cinnabar, which is a mercury sulfide. They painted it on their walls. They buried their dead in it. It's this very vibrant vermilion color.
LENTZ: The reservoirs were fed from plazas, so all the water that washed off the buildings eventually went into the reservoir, so they had mercury in their water supply. And also, we found that there was blue-green algae in a couple of the main reservoirs. So this was a big problem.
SIMON: Would it be safe to say that like so much else we discover about our own world today, what propels life sometimes can pose a problem down the road?
LENTZ: Yes, that's absolutely right. And another thing that the Maya did that probably created problems for them is that as the city of Tikal grew and grew, they had to create more agricultural land. They ended up clearing over half of their forested land. And so when the rains came down and hit the agricultural land, they lost all of that water. The rainforest would have recycled that water and kept that water going back up into the atmosphere through what we call transpiration.
SIMON: Still, you're left dazzled by the technology they devised, aren't you?
LENTZ: Absolutely. I mean, they were there for almost 2,000 years. You know, the great thing about archaeology is that it helps us understand how civilizations arise and then falter, and they all do in the end. And sometimes, what becomes sustainable for a thousand years at some point is no longer sustainable.
SIMON: Archaeobotanist and University of Cincinnati professor David Lentz, thanks so much for being with us.
LENTZ: It's really a team of people, not just me, so I thank you for giving me this opportunity. Transcript provided by NPR, Copyright NPR.