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Moments in Time, Preserved Forever: Prehistoric Footprints Reveal Uncanny Links to Our Past

A beautifully preserved footprint from Engare Sero, Tanzania. Credit: William Harcourt-Smith.

By Beth Harpaz
Editor of SUM

Paleontologists “are as much detectives as they are scientists,” said Professor William Harcourt-Smith (GC/Lehman, Anthropology) in a piece for The Conversation. He was describing the work that he and other researchers did to interpret 408 prehistoric footprints in Northern Tanzania. These tracks, preserved in volcanic ash, were made by at least 20 different humans thousands of years ago. Harcourt-Smith, who’s also a fellow at the American Museum of Natural History, co-authored a study about the footprints for Nature Scientific Reports. In this Q-and-A, he explains what these footprints tell us about our prehistoric ancestors, why you might want to download a 3D image of an ancient foot, and more.

The Graduate Center: The online images of those footprints are surreal. Those feet are between 6,000 and 19,000 years old, yet they’re as familiar as our own feet! Why is looking at those footprints so mind-blowing? And what do we know about the people who made those tracks? 

Harcourt-Smith: These people were us. They were modern humans. Their experience of the world was different, but they’re the same people as us, as a species. These footprints are absolute moments in time preserved forever. These people lived such a long time ago, but their footprints allow us to imagine this moment in time.

Rest assured, modern humans living at this time were very sophisticated — in many ways, as sophisticated as us. They didn’t have the knowledge we have; that’s an additive process. But in terms of their intellectual and social skills, they were like us. They had artistic expression and objects. They had language. They had multiple tools, complicated tools, and complex trade networks. In many parts of the world they were hunter gatherers, and more than likely, this was a hunter-gatherer band. 

This site is in a very harsh landscape with lots of volcanic ash. We did look very carefully over a huge area, but we didn’t find any artifacts. The footprints, that’s all that’s left of them. 

Footprints are all something we leave in the snow or at the beach. You think about when you’re a little kid, and you hop along behind your parents in the sand and there you are, leaving this trace. Usually they get washed way, but in this wonderful, odd site, they were preserved. 
 

GC: One of the coolest aspects of this project are the online, open-access components, including maps of the route these people took, and 3D images of their footprints. Tell us about the digitization. 

Harcourt-Smith: The digitization was very important, and the Smithsonian teams that did the digitization are phenomenal. Any educational institution, museum, or individual can download this material and view it in 3D. If they have the facilities, they can also print the footprints out in 3D and have them as tangible objects. 

The rationale for the digitization is to further (public) knowledge. As scientists, we feel strongly that you need to publish the raw data that comes with your findings. It allows people to see the evidence for themselves. Not that we’ve had any skeptics, but we do live in an age of fake news and misinterpretation of data. And we live in a world where virtual resources are becoming a central part of teaching science. It’s become a very important part of paleontology, geology, and anthropology education and outreach to make these 3D models available where possible. We are a tangible discipline, and 3D printing technology is becoming very affordable. 

Also from an ethical perspective, one ought to publish one’s data, and more journals and institutions require it in the name of transparency and visibility. Somebody else can take these scans and hopefully come up with the same results. To allow people to be involved in independent verification is a cornerstone of science.

GC: You wrote that 17 of the individuals who made the footprints were likely “cooperatively gathering food together,” and 14 of them were female, which could indicate a societal division of labor by gender, with women as foragers. How do you get all of that from footprints? It’s a bit depressing to think that even prehistoric humans had proscribed gender roles!

Harcourt-Smith: We got thousands of statistics and measurements of feet from the Army to come up with this likely makeup of women, a few teenagers, and the odd large guy from the footprints. (The size of one of the few male footprints correlates with a height of a 6-foot human.) So it’s extremely likely that this is the gender makeup. Why that is, and what the connotations are, is where it can get more speculative. We can tell this group was moving at a measured slow pace; they weren’t fleeing. We see this whole group go one way, and a few hours later, another group comes back in the other direction. It looks like they’re going somewhere, doing something, coming back. So perhaps they’re out there foraging. But there are other possibilities. 

GC: These sites have been known to the local Tanzanian Masai for a long time, but when did your team begin its research? 

Harcourt-Smith: The first researchers went to Tanzania in 2009. We wrapped up the most important work in 2012. I’ve personally been there twice, in 2010 and 2012. (A first-year GC student, Nicole Webb [Ph.D. ’18, Anthropology], participated in one of those trips.)

I’m a paleontologist on the anthropology faculty at the GC, but it takes a lot of work with other fields and specialties to get the dating correct. A site like this is very complicated: The footprints were pressed into an ash layer, then pressed into another ash layer. It took a lot of geology. We had to go back a few times to doublecheck our work and collect extra samples. At first we got dates that were very old, and we were suspicious. Then we nailed down some more accurate dates that were a little younger. We had to take our time and be very thorough. Sometimes you find something and publish it the next year; other times, it can take 20 years. 

The 2010 Engare Sero field Team
The 2010 Engare Sero field Team. CUNY faculty member Will Harcourt-Smith is third from left. (Photo courtesy of Harcourt-Smith)

GC: What happens to research like this in the COVID-19 era?

Harcourt-Smith: Fieldwork across the board, not just in paleontology but in many disciplines, has very much been curtailed. The last thing you want to do is potentially come into contact with COVID and then turn up with it in remote populations, some of which may not have access to hospitals. So there’s a big pause on fieldwork, and that creates certain problems. In terms of this particular site, one of the most important things we did was to keep the science going. By publishing right now, it’s nice to remind people of the cool work we’ve done in the past. The virtual world is so important for disseminating interesting science.

Beth Harpaz is the editor of SUM. Follow her on Twitter at @literarydj.

Submitted on: JUL 15, 2020

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