Underwater archeology reveals clues about Ice Age humans

At the end of the last ice age, glacial melt inundated human settlements near shorelines. Underwater archeologists are uncovering their artifacts.

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• 0:00Speaker 00

  WNYC is supported by Bear. Science is about asking questions, testing, trying again. It's not easy, but it's relentless. It evolves, and that's why science delivers. Learn more at sciencedelivers.com.

• 0:17Flora 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 archaeology underwater? Here to tell us more is reporter Reed Frazier from the Allegheny Front in Pittsburgh, who recently tagged along on this expedition. Hey, Reed.

• 0:57Speaker 02

  Hey, Flora.

• 0:58Flora Lichtman?

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

• 1:02Speaker 02

  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 sort of 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. And the captain of the boat goes in these straight lines for like 7 kilometers, where

• 1:41Speaker 02

  they drag this sonar equipment behind the boat to scan for suitable sites to dig. And it's pretty monotonous, you know? If you've been on a long boat ride, there's a lot of just sitting around. And one of the students, there's a lot of students on the boat, and one of the students in the cabin is reading like 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.

• 2:11Flora Lichtman?

  Yeah, I mean, this seems like a very different scene than the one we usually imagine, right?

• 2:15Speaker 02

  Yeah, the sort of-

• 2:16Flora Lichtman?

  For archaeologists.

• 2:17Speaker 02

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

• 2:26Flora Lichtman?

  What was the team looking for?

• 2:28Speaker 02

  So, they have this sonar equipment that could 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, you know, get enough food to survive about 10, 8, 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.

• 3:07Flora Lichtman?

  Did they find anything useful that day?

• 3:09Speaker 02

  Yeah, I mean, I think they did. You could kind of 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 kind of all sort of start noticing a weird line here or there. And I asked, "Okay, 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. You know, 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.

• 3:48Flora Lichtman?

  Hmm. You know, I know you report on climate change. Did working on this story change your perspective at all?

• 3:55Speaker 02

  I mean, absolutely. I think one of the things that struck me when I was talking to one of the researchers, she said, "You know, 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 kind of 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.

• 4:38Speaker 02

  It just kind of makes you kind of sit up and realize how none of the things that we think of is fixed, including like lakes and rivers and shorelines. You know, those are temporary.

• 4:50Flora Lichtman?

  Reed Frazier, energy reporter for the Allegheny Front, a public radio program in Pittsburgh. Thanks for joining us.

• 4:56Speaker 02

  Thank you.

• 4:58Flora Lichtman?

  After the break, what has underwater archaeology taught us about Ice Age America? Get excited, because we are going back in time to giant Florida. Don't go away. Science Friday is supported by Planet Visionaries, the podcast created in partnership with the Rolex Perpetual Planet Initiative. Stay tuned for a trailer and subscribe wherever you get your podcasts.

• 5:29Speaker 03

  Do you want to hear about visionaries creating a better world? People working in conservation, exploration, science, and tech, alongside storytellers imagining and creating a better future. I'm Alex Honnold, professional rock climber and founder of the Honnold Foundation, bringing you season six of Planet Visionaries. This season, I speak to guests like National Geographic photographer Tom Pescek and Anna Raffman, executive director of the Jane Goodall Institute, USA, in partnership with the Rolex Perpetual Planet Initiative. Watch Planet Visionaries on YouTube or wherever you get your podcasts.

• 6:00Flora Lichtman?

  Hey, everybody. If you like Science Friday, I want to recommend another podcast I know you'll love, too. Science vs. From peptides to protein-maxing, Science vs. takes on fads and trends and the opinionated mob—I know you know what I mean—to find out what is fact, what is not, and what's something in between. And they're the only podcast with better pun game than us. So, check them out, Science vs., wherever you get your podcasts.

• 6:33Flora Lichtman?

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

• 6:55Speaker 04

  Thank you so much for having me.

• 6:57Flora Lichtman?

  Thank you for being here. Okay, so what can we learn from digging underwater that we can't learn from regular old land archaeology?

• 7:06Speaker 04

  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 kind of 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.

• 7:47Speaker 04

  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. Like, a humongous amount of land globally went underwater.

• 8:15Flora Lichtman?

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

• 8:22Speaker 04

  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 in 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.

• 9:02Flora Lichtman?

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

• 9:07Speaker 04

  It was more— 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. Like, 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 in a huge chunk of Florida with mammoths and mastodons wandering around, with the mammoths mostly in the prairie, and the mastodons kind of clustered around the sinkholes that were being fed by the underwater aquifers, right? There would have been capyveras and beavers and short-faced bears and saber-toothed cats

• 9:51Speaker 04

  and people all over the place, kind of living in this really rich environment.

• 9:57Flora Lichtman?

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

• 10:04Speaker 04

  It absolutely has. So, one of the sites that I've been privileged enough to work on off and on over the years, the Paige Ladson site, which is in the Osala 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 mastodon, maybe butchering camel that was around the edge of the sinkhole. We don't know whether they hunted those two animals or whether they scavenged them,

• 10:46Speaker 04

  but they were cutting them apart, living around the edge of the sinkhole and going about their day. So, this was this kind of small part of human history that was just a really everyday sort of site. Not like, you know, it wasn't like people building pyramids or anything like that. It was just like 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, like 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.

• 11:28Speaker 04

  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 digesto, which is basically the stomach contents of ancient mastodons.

• 11:49Flora Lichtman?

  Wait, hold on, pause. Digesto is a technical term?

• 11:54Speaker 04

  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's stomach when it died. And as it rotted away, it kind of floated away into the pond, right? So, some of it was still in the stomachs, some of it was expelled out through the back end.

• 12:17Flora Lichtman?

  This is the term that you can use on public radio when we all know the term we're actually thinking of. But go ahead.

• 12:24Speaker 04

  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 the more formal sort of things, like 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 digesto. So, it can tell us, okay, 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.

• 13:08Speaker 04

  So, they're eating those things that are available, kind of in a semi-wet-ish environment around, like 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.

• 13:25Flora Lichtman?

  And this is, is this earlier or about the same time we thought people were there? Like, does this change the timeline?

• 13:31Speaker 04

  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 like 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.

• 14:10Speaker 04

  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 mixed 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 that, at

• 14:50Speaker 04

  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 a thousand years younger were probably people who learned to make Clovis points, but they were already here, that there were a lot of people kind of everywhere here.

• 15:18Flora Lichtman?

  I don't think of wetness as being great for preservation.

• 15:22Speaker 04

  So, what is best for preservation in archaeological contexts for organic materials? So, things that, 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, just constantness is what matters the most. So, the worst thing for organic preservation is things that call as cell walls to freeze and thaw or explode, right? But if it stays wet and doesn't freeze, it's perfect.

• 16:06Speaker 04

  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 like 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?

• 16:33Flora Lichtman?

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

• 16:43Speaker 04

  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 one-by-one meter square holes, though we would be really weird wearing wet suits and scuba gear, like 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 screens, 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.

• 17:28Flora Lichtman?

  This seems absurdly hard. I mean, when I think of just archaeology in general, it feels like a needle in a haystack problem, but this feels like another level.

• 17:38Speaker 04

  It is hard, and I do spend a lot of time talking about how underwater archaeology 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.

• 18:10Flora Lichtman?

  As a kid, did you, were you like, I want to be a marine biologist and an archaeologist? And I'll just, I'll combine them?

• 18:15Speaker 04

  No, 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 archaeologist, 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.

• 18:41Flora Lichtman?

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

• 18:50Speaker 04

  Thank you so much for having me.

• 18:52Flora Lichtman?

  This was a blast.

• 19:01Flora Lichtman?

  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, 877-4-CY-FRY 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.