Underwater archeology reveals clues about Ice Age humans

[THEME MUSIC] FLORA LICHTMAN: Hey, it’s Flora, and you’re listening to Science Friday. We’re headed to a dig site where archaeologists are looking for relics from human civilization dating back 12,000 years to the last Ice Age. But don’t picture researchers in wide-brimmed hats under the scorching sun with trowels and tiny brushes. Imagine them in scuba gear because this archaeological site is deep under Lake Erie. Why go looking there, and how do you do archeology underwater? Here to tell us more is reporter Reid Frazier from The Allegheny Front in Pittsburgh, who recently tagged along on this expedition. Hey, Reid.

REID FRAZIER: Hey, Flora.

FLORA LICHTMAN: This setup sounds wet and wild. Tell us what it was like.

REID FRAZIER: So we go out on a boat on a rainy morning from Erie, Pennsylvania, into the middle of Lake Erie. And the rain is coming down. Everyone wraps tarps around all of their equipment on this research boat. And we hunker down, and we’re out going into the lake for a couple hours. And at one point, I looked at my GPS and realized we were very close to the Canadian border, which apparently you’re not supposed to cross or you will get in trouble.

FLORA LICHTMAN: [CHUCKLES]

REID FRAZIER: And the captain of the boat goes in these straight lines for seven kilometers, where they drag this sonar equipment behind the boat to scan for suitable sites to dig. And it’s pretty monotonous. If you’ve been on a long boat ride, there’s a lot of just sitting around. There’s a lot of students on the boat. And one of the students in the cabin is reading hard copy of War and Peace, which I know takes a long time because it took me a year to read it. So if that gives you any idea of the kind of downtime there was.

FLORA LICHTMAN: Yeah. This seems like a very different scene than the one we usually imagine, right, for archaeologists.

REID FRAZIER: Yeah, digging down into sandstone in some dry desert somewhere. And yeah, this is definitely not what I thought archeology was all about.

FLORA LICHTMAN: What was the team looking for?

REID FRAZIER: So they have this sonar equipment that can kind of tell them what the soil’s like at the bottom of the lake. And they know that there is a geographic feature at the bottom of the lake about 60 feet down, that at one time was above ground and would have been a likely place where people came and tried to hunt and fish and get enough food to survive about 8,000, 12,000 years ago, in that range. And so they are looking for places to dig down, which pieces of mud to stick their pipes down into to take the coring samples.

FLORA LICHTMAN: Did they find anything useful that day?

REID FRAZIER: Yeah, I think they did. You could tell when their antennae go up and they’re all looking at the lines on the screen, which to you and me are probably just gibberish, but to them they all start noticing a weird line here or there. And I asked, OK, so what are you guys finding? And one of the researchers said, this is an old riverbed, and we wouldn’t dig here in the riverbed. But not far away, there could have been somebody’s camp where they made their tools or they hunted for caribou or big game and did lots of other things that people do.

FLORA LICHTMAN: Hmm. Yeah, I know you report on climate change. Did working on this story change your perspective at all?

REID FRAZIER: Absolutely. I think one of the things that struck me when I was talking to one of the researchers is she said, there aren’t any shorelines from 10,000 or 12,000 years ago anymore that you can dig into that are above ground. And it made me think, yeah, of course. And people live around water, or they spend a lot of time around water, at least, because that’s where a lot of our resources come from. And it puts it in perspective how rapidly things on planet Earth can change. And some of the changes that we’re seeing now, that we’re responsible for through climate change and burning fossil fuels, it just kind of makes you sit up and realize how none of the things that we think of as fixed, including lakes and rivers and shorelines– those are temporary.

FLORA LICHTMAN: Reid Frazier, energy reporter for The Allegheny Front, a Public Radio program in Pittsburgh. Thanks for joining us.

REID FRAZIER: Thank you.

FLORA LICHTMAN: After the break, what has underwater archeology taught us about Ice Age America? Get excited because we are going back in time to giant Florida. Don’t go away.

So what is underwater archeology telling us about life in the Americas 13,000 years ago? Here to dive deeper into this sunken grotto of science is underwater archeologist Dr. Jessi Halligan, who is leading the research at that Lake Erie site and studies early humans of the Americas at Texas A&M. Jessi, welcome.

JESSI HALLIGAN: Thank you so much for having me.

FLORA LICHTMAN: Thank you for being here. So what can we learn from digging underwater that we can’t learn from regular old land archeology?

JESSI HALLIGAN: That’s a fantastic question. And essentially what we can learn underwater is everything about anyone who lived on the coast from about 30,000 years ago until about 6,000 or 7,000 years ago, when sea level reached their modern elevations, right? As the glaciers melted at the end of the last ice age, they drowned the continental shelves of the entire world.

And that didn’t just happen on the continental shelves. As sea levels rose, rivers changed their bases. Lakes formed a whole bunch of waterways that did not exist 20,000 years ago exist today. And all of those places that didn’t used to have water used to be dry land that were available for all kinds of people and all kinds of places in the world, right? We have on the continental shelves and in the lakes and rivers that are now drowned, land area that is approximately the size of Australia that has gone underwater during this time period. A humongous amount of land globally went underwater.

FLORA LICHTMAN: We just heard about your Lake Erie work. Are there other hotspots for early human civilizations in the Americas that are underwater?

JESSI HALLIGAN: I would in fact argue that Erie is not known to be a hotspot. We’re the first people to do that survey there. The place where most of the research and submerged landscapes has happened in North America so far has been along the West Coast in various places. Some colleagues of mine at the University of Michigan have been doing research in Lake Huron for several years, and have now expanded into other parts of the Great Lakes. And I am the latest in a long history of people doing submerged landscape research in Florida that has been ongoing since the early 1980s or late ’70s, depending on when you want to consider the start date.

FLORA LICHTMAN: So what did Florida look like 13,000 years ago or so? Was it bigger? I guess it was bigger.

JESSI HALLIGAN: It was so much bigger. It was more than twice as big as it is today. And because the sea level was so much lower, there was more topography. Florida today is pretty flat, and offshore is also pretty flat. But if you add 200 more miles to get to the coastlines, you have a lot more space.

And so it would have been, 13,000 years ago, an open prairie and a huge chunk of Florida, with mammoths and mastodons wandering around, with the mammoths mostly in the prairie and the mastodons clustered around the sinkholes that were being fed by the underwater aquifers, right? There would have been capybaras and beavers and short-faced bears and saber-toothed cats and people all over the place, living in this really rich environment.

FLORA LICHTMAN: What have we learned from these sites? Has it changed our view of early human civilization in the Americas?

JESSI HALLIGAN: It absolutely has. So one of the sites that I have been privileged enough to work on, off and on, over the years, the Page-Ladson site, which is in the Aucilla River about 45 minutes from Tallahassee, Florida, has one of the earliest archaeological components that is known in the new world. It dates to about 14,550 years old and is evidence of humans hanging out at the edge of a sinkhole for just a little while, probably butchering a mastodon, maybe butchering a camel that was around the edge of the sinkhole.

We don’t whether they hunted those two animals or whether they scavenged them. But they were cutting them apart, living around the edge of the sinkhole, and going about their day. So this was this small part of human history that was just a really everyday sort of site. It wasn’t like people building pyramids or anything like that. It was just an everyday thing that probably these folks did hundreds of times over the course of a year.

But because it happened at the edge of a sinkhole, and it got wet and stayed wet– people were around the edge of the pond maybe even working in the shallow water. And all of the evidence they left behind got drowned in that shallow pond and stayed wet for 14,000 years. We had this really amazing situation where the remnants were preserved. So it wasn’t just stone tools. It was stone tools and all of the bones of these animals. And they were resting in a bed. That is what we call digesta, which is basically the stomach contents of ancient mastodons.

FLORA LICHTMAN: Wait. Hold on. Pause. “Digesta” is a technical term?

JESSI HALLIGAN: It’s the more polite term because some of it probably came out the end of the elephants while they were hanging out around this pond, but some of it was probably actually in the mastodon stomach when it died. And as it rotted away, it floated away into the pond. So some of it was still in the stomachs. Some of it was expelled out through the back end.

FLORA LICHTMAN: This is the term that you can use on Public Radio, when we all know the term we’re actually thinking of. Go ahead.

JESSI HALLIGAN: Yes. And I’ve got to tell you, you can make really good friends with eight-year-old boys if you can give them a little bag of mastodon poop to keep with them for the rest of their lives. But to get back to more of the more formal things, this was really a great opportunity for archaeologists because it is an everyday event, but also because we were able to radiocarbon date each individual piece of that digesta.

So it can tell us, OK, when did this elephant die around the edge of this pond, and also, how did the environment change over time? And what were they eating? What was their health like? All of those kinds of things, which turns out they were probably there in the late fall because there were a bunch of gourd seeds and grape skins and grape seeds in there. So they’re eating those things that are available in a semi-wet-ish environment around in the late fall. And so probably that’s when the people were there too, and it’s just as part of their seasonal round following these big herd animals and/or going from waterhole to waterhole.

FLORA LICHTMAN: And is this earlier or about the same time we thought people were there? Does this change the timeline?

JESSI HALLIGAN: Well it has changed the timeline. So when the original excavators published their research back in the early 2000s, it was sort of ignored because there was this really dominant idea of human settlement in the Americas, and those people were known as Clovis people because of these big spear points that were originally found in Clovis, New Mexico in the 1930s. And so for many, many years, the dominant idea from the 1930s until the mid-2000 was that Clovis people were the first people on this continent.

The oldest Clovis dates that we have, being the most generous, are about 13,200 years old. So an archaeological site that’s 14,550 years old is significantly older than that. And that really did challenge some of the paradigms. And some archaeologists still think that there are questions about this site. They think the fact that we had to dive 30-feet deep into a watery sinkhole means that we don’t understand what we saw maybe. Or maybe there were some kind of geological processes that we don’t understand that mix things up and made the dates wrong and so our site isn’t as old as we say it is, because how could it possibly be that much older than Clovis?

Everything we have found to test the site so far makes it really clear that at least the mastodon poop was 14,550 years old. And the artifacts within it were really well sealed in layers that were not messed up. And so it really does change things. Because if a site in the middle of nowhere in Florida is 14,550 years old, that means that Clovis people 1,000 years younger were probably people who learned to make Clovis points, but they were already here, that there were a lot of people everywhere here.

FLORA LICHTMAN: I don’t think of wetness as being great for preservation.

JESSI HALLIGAN: So what is best for preservation in archaeological contexts for organic materials, so things like plants and animals and bones and all of that, the things that are best for that kind of preservation are constant environments. So if something is buried immediately after it’s left behind, and what it’s buried in stays the same temperature or the same humidity or stays– this just constantness is what matters the most. So the worst thing for organic preservation is things that cause the cell walls to freeze and thaw or explode.

But if it stays wet and doesn’t freeze, it’s perfect. Like, look for instance at the underwater shipwrecks in the Great Lakes. They are some of the best preserved shipwrecks anywhere in the world, even though it freezes every winter up North because it’s cold, dark water that doesn’t change its conditions over time. Or the bog bodies in Ireland, they got into the wet, and they stayed wet until people found them. And they’re so well preserved compared to other places, right?

FLORA LICHTMAN: We heard a little bit from Reid about the sonar part of your work, looking for sites. Do you also strap on scuba gear and bring a pickaxe underwater?

JESSI HALLIGAN: Not a pickaxe. But yes, we wear scuba gear regularly. If you saw us doing our underwater excavations, if you could drain the water, we would look just like archaeologists digging on land. We dig in 1-by-1 meter square holes, though we would be really weird wearing wetsuits and scuba gear. We’d be weirdos.

But the process is the same. We dig in square holes, using trowels to dig the dirt. And our dirt goes away. Instead of using a dustpan and a broom to put the dirt into a bucket and carry it off to screen, we have these things called induction dredges that basically vacuum the loose dirt and send it up to the surface, where people are looking at it for any artifacts or bones we might have missed.

FLORA LICHTMAN: This seems absurdly hard. When I think of just archeology in general, it feels like a needle-in-a-haystack problem, but this feels like another level.

JESSI HALLIGAN: It is hard, and I do spend a lot of time talking about how underwater archeology is a stupid sport because we have small engines, and we have to deal with weather, and we have to deal with what the waves are doing. In some places you have to work when the tide’s high or when the tide’s low and not any other time. It is hard. But the reason why it’s worth it is because it’s the only place you can answer some of these questions about human history, right? And so hard doesn’t mean not worth doing, I guess.

FLORA LICHTMAN: As a kid, were you like, I want to be a marine biologist and an archeologist, and I’ll just– I’ll combine them?

JESSI HALLIGAN: No, not at all. I was 18 years old the first time I saw an ocean. I grew up on a cattle ranch in the middle of South Dakota. And I knew I wanted to be an archeologist. And I knew I wanted to study Indigenous people in the Americas because that was the landscape I grew up on and in the world I grew up on, right? But I had no idea that I was going to end up having to learn to scuba dive to do it.

FLORA LICHTMAN: [LAUGHS]

Dr. Jessi Halligan, underwater archeologist and associate professor at Texas A&M in College Station, Texas. Jessi, thank you so much for joining me today.

JESSI HALLIGAN: Thank you so much for having me.

FLORA LICHTMAN: This was a blast.

Before we go. The most wonderful time of the year is right around the bend. That’s right. Cephalopod Week is coming up, and we are planning a squid, octopus, cuttlefish blowout. And we want your burning cephalopod questions, deep or shallow, flashy or hiding in plain sight. We will get you some answers. So call us– 877-4SCI-FRI is our number– with all of your octopus, squid, and cuttlefish questions. This episode was produced by Kathleen Davis. We’ll catch you next time. I’m Flora Lichtman.

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