Dr. David Gwynn
speaker
906 appearances
4 recordings
1 series
first heard Nov 2024
last heard 21 Dec
Dr. David Gwynn’s voice in public audio — every appearance, attributed to the second.
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Well, I think that argument is just flat wrong in terms of human impacts. Look, there's lots of reasons to doubt that humans had an impact on these animals, right? And the entire ecosystems, I'm guessing as well, yeah. Well, okay. Thank you. Because in fact, we're talking about 38 different genera in North America alone.
And the estimates of how many animals were out there range upwards of 100 million animals. And you've got a small band of hunter-gatherers coming in with sticks and sharp rocks. I'm exaggerating to make the point here. They're coming into a landscape that they still don't fully understand, that they still don't fully know well.
And as a wonderful archaeologist by the name of George Frizen, who actually did subsistence hunting as a child in the 1920s, has said, to successfully match wits with wild animals with the intent to kill them requires a thorough knowledge of the hunting territory and the behavioral patterns of that animal. And you're not going to get that as you're running pell-mell through the hemisphere, right?
And further, that as a hunter-gatherer, when you're coming into a new landscape, this is not like, let me use a sort of a Civil War analogy. where William Tecumseh Sherman, a Union general, basically burned his way through Georgia on his march to the sea. 62,000 men marching 300 miles just basically devastated everything in a swath about 50 miles wide.
The hunter-gatherers coming into the Americas were not an army, right? They were not able to sort of devastate the ecosystem like that. But really, this all comes down to the empirical test. If overkill, if the notion that people were responsible for Pleistocene extinctions is correct, we should see ample evidence of kill sites, right?
We've got 38 different genera, possibly tens if not hundreds of millions of them. We ought to see dead bodies all over the place with Clovis points stuck in them. And if, in fact, humans were responsible, then the extinction of those 38 genera should all have occurred within the window in which human hunters arrived and spread throughout the hemisphere.
Oh, those are the weapons that are used by the folks who are blamed for the extinction, right? This is the first group of serious hunter-gatherers that we see. They come into the Americas sometime around, they are in the Americas, let me correct myself, around 13,000 years ago. They're around for 500 to 1,000 years, depending on where you are in the continent.
The Clovis point is the so-called smoking gun of the whole extinction scenario, all right? Okay, so we've got our two empirical tests. We should see lots of kill sites and the animals should all go extinct basically simultaneously, coincident with these Clovis groups, okay? All right, so the first test. We have looked at all of the claimed...
Sites for which it is said humans are responsible for the death of one of these giant animals. And there's about almost 100 of them. Of those claimed sites, only 16 of them actually give clear, compelling, and secure evidence that people were responsible for the death or the scavenging of the animal that was found there.
There's another element of that, which is that of those 16 kill sites, there's only mammoth, mastodon, gompothere, which is a form of mastodon, camel, and horse. Camel, wow. Yeah, Pleistocene camels. Pretty cool, huh? So there's only five of the 38 genera. have been found in these sites. What about the other 33?
We have absolutely no evidence of any kind of interaction of humans with these animals. Then the second issue, the timing issue. What we see is that most of these animals are actually not well dated. We know that only a limited number of them have radiocarbon dates. And of that limited number, less than half of all those animals
survive of those 38 genera, survive up until the time humans arrive, which means that some of them may have been gone long before people actually showed up on the landscape. So, how could they be responsible for the disappearance of an animal that happened 6,000 years before they even got there? There's a couple more pieces to that, okay?
So, the timing issue doesn't work, the kill site issue, not enough, right? We also know what extinctions might look like in terms of the kill site record. And let me explain. Humans have been hunting bison for 12,000, 13,000 years. And they've been hunting them in sometimes large numbers.
There are sites in Colorado that are 10,000 years old for which we have 190 bison that got stampeded into an arroyo and died a horrible death. I mean, you've got skeletons that are on their backs and they were clearly riding around, but they were then piled on by three or four other layers of bison. It must have been a terrible way to go.
There's a site in southeastern Wyoming, it's a sinkhole where an estimated 10,000 or more bison were stampeded into the sinkhole repeatedly over several centuries. And yet, after all that intensive hunting, bison are still around. So here we have a record of
heavy-duty almost, I hesitate to use the term industrial scale, but heavy-duty hunting of a species for 12,000 years, but it didn't go extinct. And yet people claim that these 38 genera of animals for which we have only 16 sites giving us evidence that they were hunting went extinct and they call that or they blame that on humans, that seems kind of unlikely.
Lots of stuff is happening at the end of the Pleistocene. We've got an increase in the amount of incoming solar radiation, a rapid rise in atmospheric CO2. We've got warmer climates. Patterns of seasonality are changing. So we're getting, in some areas... which had been sort of relatively mild winters, relatively mild summers. We're now getting really, really cold winters, really hot summers.
We're changing moisture regimes. Ecosystems that had been in place for literally thousands of years are fragmenting because in response to these changes in the climate, species are going off in different directions depending on their ecological tolerances and their thresholds, right? You've got feedback effects because when megafaunal populations die off, they're no longer clearing out
certain types of vegetation from an environment. So you've got changing habitats, you've got changing competitive relationships. So lots of different things are happening in the environment. The real tough question is how do you link that to the processes that would have led to the extinction of these animals.
And the first thing that you need to do is recognize there's not going to be a one-size-fits-all solution to this problem because each animal, each of those several dozen genera of large mammals, which includes actually a number of small animals, which includes, for that matter, trees going extinct at the end of the Pleistocene, turtles going extinct, snakes going extinct.
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