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Tech is speeding up the search for ships — and stories — from the trans-Atlantic slave trade
Feb 22, 2022

Tech is speeding up the search for ships — and stories — from the trans-Atlantic slave trade

As the cost of advanced technology has fallen, marine archaeology has become more accessible. "When we uncover these ships, it causes a resurgence of memory in communities," said anthropology professor Justin Dunnavant.

Some of the history of slavery in the Americas still rests on the ocean floor, in the form of sunken ships that once carried captives to the U.S. or the Caribbean region — for lives of enslavement, at least for those who survived the crossing.

Marine archaeologists and a small army of scuba divers are working to uncover those stories, using the latest technology to locate some of those ships and add more context to history. A new podcast from National Geographic, “Into the Depths,” features the experiences of some of these divers.

One of them is Justin Dunnavant, an archaeologist and assistant professor of anthropology at the University of California, Los Angeles. He joined “Marketplace Tech” to explain how advances in technology are changing his work.

Justin Dunnavant: We’ve seen maritime archaeology develop rapidly over the last 50 years. Really a lot of it has been a reduction in the cost of the technologies that we use and a reduction in the cost of doing the surveys. And so we have been able to use advanced technologies, like side-scan sonar, which gives us a reading of the bottom of the ocean floor, as well as a magnetometer — which is essentially a giant metal detector that we can attach onto the back of our boats to pick up metals, similar to the way that you would on a beach or in a field with a handheld metal detector.

Kimberly Adams: When you say that cost has gone down, can you give some comparisons?

Dunnavant: Oh, man. I tell people we’re like sort of ex-construction workers in many cases, in the sense that a lot of the technologies we use are actually also used in construction or development projects. On land, I know that anybody who’s done survey work, or you see people on the sides of the roads with these tripods that are shooting lasers into a prism. That total station machine used to cost upwards of $20,000 to $50,000. Now, you can find them as low as $5,000 in some cases. And the accuracy has improved so much. We can get measurements, you know, up to 2- to 3-centimeter accuracy.

Adams: That tech helps you locate where the shipwrecks may be, but then what?

Justin Dunnavant  smiles for a photo with a computer monitor in the background.
Justin Dunnavant (Susan Urmy)

Dunnavant: Then, it’s incumbent upon us to actually scuba dive onto the wreck. The mapping component is probably the most low-tech that we get. We normally just go down with a slate, a No. 2 pencil and Mylar paper and start to sketch away what we see underneath the water. There are new technologies that are developing. A lot of people are starting to use what we call photogrammetry now, where we take underwater cameras and shoot hundreds of photographs of a site and then throw it into a software package that compiles them into a 3D image. But that doesn’t really work too well for these flat wrecks. You can imagine what a 3D image of a two-dimensional object would be. So that’s when, again, we go back to that pencil and slate technology.

Adams: What are you trying to learn from finding and mapping the slave ships in particular?

Dunnavant: Yeah, I mean, one of the most important things we try to do is we often treat these wrecks almost like plane crashes, and we’re trying to re-create the wrecking event. On the one hand, a lot of times these wrecks occurred because the ships would hit a reef or hit something underneath the seafloor, which would cause it to fall apart, break apart, and then eventually sink. We are looking for objects and artifacts that could tell us more about what was actually on the ship when it went down. And then the other elements of this — and this is with all the archaeological work that we do — we’re trying to reactivate these stories into popular memory. A lot of people don’t really think about slavery on a day-to-day basis, they don’t think about the ramifications of it, and they don’t think about their connections to it. But when we uncover these ships, it causes a resurgence of this memory in communities. And then people start remembering conversations they’ve had with parents or grandparents or things that they may have read about their own local histories.

Adams: What was the most meaningful dive for you that you’ve done so far?

Dunnavant: Actually, I would say the most meaningful dive wasn’t even really a dive. I had the opportunity to go over top of the Clotilda, which was the last slave ship to enter the United States. I was on the boat with a descendant of somebody whose ancestor was enslaved on the Clotilda, as well as a descendant of the captain of that ship. And that was the first time they had met, and it was the first time they had been to the site together. And again, I think that is probably one of the most memorable moments because it was a moment where we’re starting to have these intergenerational conversations about memory and repair and what kind of history we can actually learn and develop together if we stay committed.

Adams: Some of your work also deals with not just the ships themselves, but also some of the knock-on effects of the trans-Atlantic slave trade. Can you talk about that?

Dunnavant: I would say actually the bulk of my research is studying and exploring the environmental impacts and the environmental ramifications of the trans-Atlantic slave trade, as well as trying to locate and understand how it is that enslaved Africans were using the landscapes that they found themselves in. We are using some advanced technologies right now, including lidar, which stands for light detection and ranging. These are satellite images and can give us a 3D scan and reading of the geography, and we’re using that to then create 3D models, digitizing historic maps and overlaying them so that we can better understand not only where it is that people were living, but perhaps where it is that enslaved Africans were running away to and establishing their own independent camps.

Adams: You mentioned earlier that the cost of some of this tech is going down. How does this decreasing cost factor into who gets to do maritime archaeology?

Dunnavant: It’s giving us wider access to who it is that can do this work and what stories we can tell, more importantly. Because it was so costly, we had to focus on the larger sites such as the Titanic. But now that costs have gone down, we can focus on the smaller sites, the more mundane histories that really surface and stay around local communities. And that can give us insight into a whole range of other stories that we didn’t even have the ability to think about, you know, 15 or 20 years ago. Universities are expanding their programs and training in maritime archaeology. More people are getting into scuba diving and swimming, which is causing them to ask interesting questions and search for more sites. So, it’s really opening us up to a new space, and it’s an exciting future ahead of us.

Dunnavant was featured in a recent episode of that National Geographic podcast, “Into the Depths,” which explores the work of Diving With a Purpose, a group of Black divers who travel the world helping to locate, map and memorialize the sites of wrecked ships that carried enslaved Africans.

Dunnavant also does work with the Slave Wrecks Project, an initiative by the National Museum of African American History & Culture, which also works to study sunken slave ships to tell more nuanced stories of the trans-Atlantic slave trade.

Marine archaeologists don’t just study ships. Dunnavant told me the story of a Tuskegee Airman’s plane that was discovered in Lake Huron a few years ago. You can hear a 2017 Michigan Public Radio interview with one of the divers who explored the site. In a bit of serendipity, that wreck was discovered exactly 70 years to the day the plane went down.

There is history in the water, and technology is making it easier to find.

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The team

Michael Lipkin Senior Producer
Stephanie Hughes Producer
Jesus Alvarado Assistant Producer