Dr. David Gwynn

With ancient environmental DNA, you know when the plants show up. You know when the animals showed up.

With ancient environmental DNA, you know when the plants show up. You know when the animals showed up.

With ancient environmental DNA, you know when the plants show up. You know when the animals showed up.

Sorry about that. Yeah, we go to a lake, we drill, we get a core of sediment, this tube of sediment, and you slice it up like a salami, right? And then you look at what the DNA is in the different slices that are of different ages. And what we found was that that corridor was not biologically viable until around 13,000 to 12,500 years ago.

Sorry about that. Yeah, we go to a lake, we drill, we get a core of sediment, this tube of sediment, and you slice it up like a salami, right? And then you look at what the DNA is in the different slices that are of different ages. And what we found was that that corridor was not biologically viable until around 13,000 to 12,500 years ago.

Sorry about that. Yeah, we go to a lake, we drill, we get a core of sediment, this tube of sediment, and you slice it up like a salami, right? And then you look at what the DNA is in the different slices that are of different ages. And what we found was that that corridor was not biologically viable until around 13,000 to 12,500 years ago.

And of course, we've had people in the Americas already for a few thousand years. So what that tells us is that the ice-free corridor was not the initial route into the Americas because it didn't become a route and available until well after people had already been here, which tells us they must have come down the coast.

And of course, we've had people in the Americas already for a few thousand years. So what that tells us is that the ice-free corridor was not the initial route into the Americas because it didn't become a route and available until well after people had already been here, which tells us they must have come down the coast.

And of course, we've had people in the Americas already for a few thousand years. So what that tells us is that the ice-free corridor was not the initial route into the Americas because it didn't become a route and available until well after people had already been here, which tells us they must have come down the coast.

Yeah, exactly right. This was a very, very different landscape at the end of the Pleistocene. The land bridge itself, I mean, look, for all intents and purposes, if you walked from Northeast Asia and Siberia into Alaska, you wouldn't have noticed the difference in terms of the environment. It was cold. It was dry. It was a grassland.

Yeah, exactly right. This was a very, very different landscape at the end of the Pleistocene. The land bridge itself, I mean, look, for all intents and purposes, if you walked from Northeast Asia and Siberia into Alaska, you wouldn't have noticed the difference in terms of the environment. It was cold. It was dry. It was a grassland.

Yeah, exactly right. This was a very, very different landscape at the end of the Pleistocene. The land bridge itself, I mean, look, for all intents and purposes, if you walked from Northeast Asia and Siberia into Alaska, you wouldn't have noticed the difference in terms of the environment. It was cold. It was dry. It was a grassland.

The tundra, as we think of it today, is a much more geologically recent phenomena. And it has to do with warming and increased precipitation and that kind of thing. So during the Pleistocene in Alaska and across the entire land bridge, you had horses, you had mammoth, you had giant bison. And these are animals that needed to be dry underfoot. right?

The tundra, as we think of it today, is a much more geologically recent phenomena. And it has to do with warming and increased precipitation and that kind of thing. So during the Pleistocene in Alaska and across the entire land bridge, you had horses, you had mammoth, you had giant bison. And these are animals that needed to be dry underfoot. right?

The tundra, as we think of it today, is a much more geologically recent phenomena. And it has to do with warming and increased precipitation and that kind of thing. So during the Pleistocene in Alaska and across the entire land bridge, you had horses, you had mammoth, you had giant bison. And these are animals that needed to be dry underfoot. right?

These are not animals that do very well on tundra. Caribou do great on tundra, but they're really not around during this time in the numbers that mammoth and horse and bison are.

These are not animals that do very well on tundra. Caribou do great on tundra, but they're really not around during this time in the numbers that mammoth and horse and bison are.

These are not animals that do very well on tundra. Caribou do great on tundra, but they're really not around during this time in the numbers that mammoth and horse and bison are.

Well, exactly right. These were diverse landscapes. You've got everything from vast grasslands to deep forest and forests that vary tremendously in terms of the nature of the vegetation. You've got boreal forests, you've got deciduous forests, you've got, as you go further south, of course, you're getting into tropical stuff.

Well, exactly right. These were diverse landscapes. You've got everything from vast grasslands to deep forest and forests that vary tremendously in terms of the nature of the vegetation. You've got boreal forests, you've got deciduous forests, you've got, as you go further south, of course, you're getting into tropical stuff.