Tom Sever, archaeologist

NASA's only archaeologist explains why the Maya matter, how satellite images can find underground paths, and why he doesn't have time for Indiana Jones. Interview by Massie Santos Ballon

May 25, 2008

Photo courtesy of NASA

If you Google "Tom Sever," the image that pops up is a man in sweat-stained khakis and rain hat who seems to be looking for a bullwhip. In person, however, Sever looks more like Tom Selleck than Indiana Jones.

Perhaps best known for his work with Mayan ruins in Central America, Sever, 59, attended seminary school to become a Catholic priest. He quickly found another calling watching the night skies. With graduate degrees in archaeoastronomy and anthropology, he has plied his trade for NASA for nearly 30 years. He's currently based at the Marshall Space Flight Center in Alabama.

Sever pioneered the use of computer software to read satellite images of the Earth and identify ruins all over the world, using a technique known as remote sensing. The computer processes grayscale digital images from satellites; the user slides the data through a series of mathematical functions to reveal features that otherwise might remain hidden. "The advancement is not in the sensors themselves, but in our capability to process and find information in a wide range of data," Sever says.

In the 1980s, Sever used Landsat images to identify Mayan sites near a proposed hydroelectric dam project on a river along the Mexico-Guatemala border. The images also revealed that Mexico's forests were decimated, while Guatemala still had rainforest cover. His work was instrumental in creating the Maya Biosphere Reserve, an international conservation and sustainable development collaboration between Mexico, Guatemala, and Belize.

In seminary school, Sever says the priests used to end each class by asking whether anyone other than "Doubting Thomas" had any questions. After he spoke in Boston at the February 2008 meeting of the American Association for the Advancement of Science (AAAS), he agreed to have the tables turned and answer a few himself.

Much of your research, especially in recent years, focuses on the Maya. What's the appeal of studying them?

It's the greatest demographic disaster in human prehistory. This great civilization mastered the forest for centuries — how did they do it? What in the world caused them to die off so quickly? A lot of my research now is modeling, where we're reconstructing how the Maya were able to feed this landscape. By running these models we're able to figure out how they sustained it, how the climate and the landscape changed around them, and then apply it to Central America today or tropical forests around the world. In other words, the thing about archaeology is that for the first time it's relevant. We're working with climatologists and atmospheric modelers and putting the human dimension in these research areas.

That's interesting that you say for the first time archaeology is relevant.

Relevant in a major way. What happened is that at a global scale, archaeologists around the world using this technology and working with modelers could start to learn about human adaptation in the past and in the present, and what might come in the future.

At AAAS, you mentioned you are going back to the bajos [seasonal wetlands] of Guatemala in April. What do you expect to find there?

One of the questions we have is: How did the Maya manage water? We're finding canals and so forth that they used to store water in. We sent the image to a stream morphologist and a hydrologist and a geologist. They all agree that those features are manmade, but we have to go confirm that.

"When I come home [from the field], I am really chewed up. You literally have ticks on you by the thousands if not millions, and that's not an exaggeration. Mold grows on you and so forth. My wife gives me my own bedroom for about two weeks."

Do you visit the site every year?

I've been going to the field every year since 1987 to visit Guatemala, and Costa Rica since 1985, but not every year. Last year I was in the Amazon.

I had imagined that you just look at a satellite photo and pick out various features. It sounds like it's not always so easy.

Everyone thinks the satellite images they see are just how they came off the satellite. That is not the case at all. A lot of these features are difficult to extract and find. A lot of people simply wouldn't know what they're looking at.

Can you give an example of an image people keep misinterpreting?

No, but on the positive side, the image I showed [at the AAAS talk and which led to the Maya Biosphere Reserve] caused the presidents of Mexico and Guatemala to shake hands. In the same way when [University of New Hampshire archaeologist] Bill Saturno and I mapped all the Maya sites in this region, everybody in Maya archaeology said, "Wow, I didn't know you could do that." But it's always been a challenge. In 1985, the head of Harvard's anthropology department told me my problem was that I was trying to bring math and science to a group of people that became archaeologists because it didn't require math.

Have you come up with a good response for him since then?

To this day a lot of archaeologists still don't understand the technology. The difference is this: If you were to go to the jungle to do fieldwork by traditional methods, you would get 10 people in a line and walk forward. Every 50 feet, you'd dig a shovel in the ground to see if you could find anything. You can't cut the vegetation to begin with, and a lot of the features we're looking at are invisible to the naked eye. We're able to see where these things are first, then send people out weeks in advance to cut the footpaths so we don't stand there and swat mosquitoes for a week.

This remote sensing technology requires that you go to the field a lot. Is that part of the work's appeal?

When I was young it was. Now traveling has become such a difficulty with airlines as a result of 9/11. It's just a real annoyance now. But once you get there, seeing different cultures and different people is a fun part of the job.

What's your favorite place?

My favorite place to work is in Peru, the Andes in Peru. I just think it's the most beautiful place on Earth. I've worked in Israel, and my dissertation was on Chaco Canyon, New Mexico, but I just love the Andes.

You mentioned that fieldwork is more difficult in a tropical forest. Could you talk about some of the challenges you face when you're working in dense vegetation?

The heat is intolerable. There's all kinds of dangerous things — poisonous snakes, killer bees, deadly 4-inch wasps. One of our guys was stung on the hand and I thought he was dead. We were up with him all night. When I come home, I am really chewed up. You literally have ticks on you by the thousands if not millions, and that's not an exaggeration. Mold grows on you and so forth. I'm talking about the fieldwork where you're in a hammock every night and you can't bathe and start getting a little gritty. My wife gives me my own bedroom for about two weeks and she looks at my stuff, all my clothes. I have to pour it out in the driveway, and she takes sticks and figures what can be bleached and saved and what goes into the trashcan immediately.

Has she become an expert in figuring out what kinds of strange and interesting insects you bring home?

No, but I have malaria, so you come down with these things. In anthropology, the reason we never talk about this stuff is because the people who live there go through this every day. It's not fantasized; they die and no one cares. So that's why we never highlight the conditions. It's just almost unethical.

So how big is the first aid kit you carry around?

I never carried antivenin for the fleur de lance snake, so I just presumed that when it happened, I was dead. I've known several people who have died from fleur de lance snakebites.

I heard you'd been approached to do a 30-year retrospective program of Indiana Jones — and turned it down.

How did you find out about the Indiana Jones thing?

When I came into the AAAS meeting room, you were discussing it with somebody.

Why don't I do that? The answer is time and editorial control. I get approached by a bunch of these. The History Channel, for instance, wants to do a 13-part series which would take three-and-a-half months of filming. It's time I don't have. And these programs, they're a whole bunch of independent competitors who go out and make programs, then they try to sell it to Discovery. So the more interesting they can make it, the better. Companies will buy it, and they get a bigger audience. They will use something that will make you look absolutely ridiculous, and most people will think you really believe that. The other part is just personal. I hate attention. I've addressed Congress — presented my research to them. I don't get nervous lecturing, but I just don't like any attention at all. My idea of hell is to go to a Mexican restaurant and the staff comes out singing "Happy Birthday." There are people who love that attention. Not me.

Massie Santos Ballon, a graduate student in the Science Communication Program at UC Santa Cruz, earned a B.A. in molecular biology and biochemistry from Wesleyan University. She writes a regular science column for the Philippine Daily Inquirer. She has worked as a reporting intern at the Monterey County Herald, the Stanford University News Office, and, an online newsletter about the clean technology industry. Massie will work in Mountain View, CA, this summer as a writing intern at 23andMe, a personal genetics analysis company.

© 2008 Massie Santos Ballon