So – What Happened?

Between 10 and 12,000 years ago, the world changed.  In North America, 35 genera of large mammals became extinct.  Not species, but genera – whole groups of closely related species.  Thirty five genera:  Mammoths, mastodons, giant sloths, horses, saber-toothed cats, the short-faced bear (but not grizzlies), the American lion (but not the Mountain lion), camels (but not llamas and vicunas in South America), the giant beaver, but not the regular little guy.

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So – what happened?  Where’d everybody go?  And why?

For years, paleontologists and archeologists have tried to figure this out.  There have been five main theories to explain this wholesale extinction:

  1. Overkill – to much hunting by the newcomers to North America, the so-called Clovis people;
  2. Environmental change;
  3. Disease;
  4. Some extraterrestrial impact, akin to the comet which is believed to have killed the dinosaurs;
  5. Some combination of any of the above.

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One issue that has come up, because of the paucity of fossil remains, and gaps in the fossil record, is the timing of these extinctions.  Did these genera go extinct at roughly the same time, or were these extinctions staggered, spread out over time? Was this a slow catastrophe, or a fast one?

In 2009, two scientists, J. Tyler Faith and Todd Surovell, took a look at this issue, and published an article titled Synchronous Extinction Of North America’s Pleistocene Mammals, in PNAS, vol. 106, no. 49.  No slouchy journal, either – PNAS means Proceedings of the National Academy of Sciences of the United States of America.

By doing a careful statistic analysis of the fossil remains associated with the extinctions, they concluded that “the combination of these lines of evidence suggests that North American late Pleistocene extinctions are best characterized as a synchronous event.”  Specifically, “our analyses demonstrate that the structure of the chronology of North American late Pleistocene extinctions is consistent with the synchronous extinction of all taxa between 12,000 and 10,000 radiocarbon years. B.P.”

Okay, so what does that mean?

It means that most of these animals all became extinct in a two thousand-year span.  The authors note that:

         “Our simulations do not rule out the possibility that some extinctions may have occurred before 12,000 radiocarbon years B.P. The biogeographic simulation suggests that anywhere from 0 to 8 genera could have disappeared before the terminal Pleistocene . . . Even so, 23–31 genera abruptly disappeared at approximately the same time. Our results leave open the possibility for a small level of background extinctions (0–8 genera) followed by a surge in extinction rates that wiped out the remaining taxa (23–31 genera) between 12,000 and 10,000 radiocarbon years B.P.”

So it is possible, they acknowledge, that of the 35 genera that became extinct, maybe as many as 8 of them had gone extinct earlier that 12,000 years ago.  That still means, however, that 27 of them became extinct in that short – remarkably short – period of time.  As the authors put it,

           “Whether or not background extinctions took place, that a catastrophic event or process occurred at the end of the Pleistocene is abundantly clear.”

The implications for this are important.  Whatever happened, it happened very fast, and was continent-wide.  Europe experienced what the authors call a “long-term, piecemeal extinction process.”  Not so, here.  It happened all across the continent, in what they call “a geologic instant.”

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This conclusion doesn’t necessarily eliminate any of the five possible causes of the mass extinction, but it does put certain constraints on them.  An environmental change, for example, if it was the primary cause of these extinctions, must have been nation-wide and very rapid.  But intriguingly, even those limits – speed and breadth – still fit with three of the possible causes for the extinctions:  “This time period encompasses the earliest secure evidence of human foragers in North America . . . the Younger Dryas cold interval . . . and a possible extraterrestrial impact.”

Well, science marches on.  We still don’t know why these extinctions occurred.  And while two thousand years may be a geologic instant, in the lives of these animals, it encompassed tens or hundreds of generations.  A drought that lasted five hundred years, or seasons so cold that plants wouldn’t grow, could certainly have caused some of these extinctions.  And there may have been a cascade effect, too:  If a given herbivore becomes extinct or vanishingly rare, then the predator that preys on it is in trouble, too.  And family structures may have been disrupted by hunting, too, for that matter:  If the matriarch of the mammoth herd is killed, maybe the young ones don’t know how to survive a particularly harsh winter, or a dry summer.

But as to what happened?  We still don’t really know.  As Faith and Surovell put it, “further research on the biogeographic histories of individual species in relation to detailed paleoclimatic, paleoecological, and archaeological data could help to finally pin down the cause of North American end-Pleistocene extinctions.”

The Clovis Mission: Ch. 5: Summers

Rain.  Sheets of rain.  Downpour.

 “Ah, shit.”  Lasher spoke. “C’mon, move it!  We gotta get this shit packed up.”   So right away, even before we looked around, the three of us scrambled around and loaded the horses, and saddled the horses, and put on rain clothes, and generally ran around like idiots, until everything was squared away.  Jack was wet, shivering.  And then, of course, the rain stopped.

And I looked around, for the first time, at North America, roughly 12,000 years ago.  You’ve never experienced anything like this.  The air smelled unbelievably fresh and cool.  The sky was clearing and a brisk wind was blowing.  I could see low hills, obscured a little by the mist that was breaking up.  It was cool, morning, early spring.    A couple birds flashed by, but I couldn’t tell what they were.  Bird song – lots of bird song. The country was lightly wooded.  We were still so close to the Mississippi that trees could grow.  The trees were just budding out.  I saw oaks, hickory, a couple willows down in a stream bed near us.

The horses stamped, and a little steam rose from their coats.  Lasher looked around.  We all looked around.  Jack trotted around us, head down, sniffing avidly.  I found I was grinning. Devereaux laughed a little.  Even Lasher smiled.  After a minute or two, Lasher said “All right, let’s get going.”  So we mounted up and set off. 

The first night, we built a small fire, and set up camp for the first time, on a low rise, in a grove of oaks. And started talking. Lasher did, anyway.  He sat there, drinking tea, and asked me, “So, what are we up against?”  I turned.  “What are we likely to encounter out here?” he said.  “I’ve read some about the Pleistocene, but I’d like to hear what you can tell us.  Hey, Devereaux – listen up!”  Devereaux had been futzing around with one of his rifles, but he stopped, and came over to where we were sitting.

“Well,” I said, “that’s really the sixty-four thousand dollar question, isn’t it?  No-one really knows.  I mean, we have fossil evidence of all kinds of animals, most of whom are now extinct  – extinct in our time, that is.  But there’s tons of stuff we don’t know. “

“What kind of animals?”

“Lots.  Lions, bigger than African lions; bison – like superbison – bigger than today’s.  Camels, horses, cheetahs, hyenas, sloths. Saber toothed cats; a giant bear – the short-faced bear – probably the biggest land predator alive in this time.  Mammoths.”

“Jesus Christ,” Devereaux said.  “It’s the American Serengeti.”

“Yeah, and other animals, too. Only, we don’t know nearly enough about them – how many there were; how they lived, how they hunted.  Almost nothing.  That’s one thing Carver was back here studying.”

“Yeah, or why they went extinct.” Lasher said.

“That’s right – we don’t know why that was. “

“Maybe the cavemen wiped them out,” Devereaux said.

“Well, they weren’t really cavemen,” I said. “The people of what we call the Clovis culture were some of the earliest settlers in North America.  We’ve found their stone points, sometimes associated with the skeletons of mammoths.  But again there is still a lot we don’t know.  Where’d they come from?  When?  How?  How did they live?  Where?  How many were there?  This stuff, too, Carver was supposed to be researching.”

“Okay,” Lasher said “Big animals, and lots of ‘em.  How will they react when they see people?  Do we have to worry about ‘lions and tigers and bears oh my?’”

“Yeah, and what about the natives,” Devereaux asked.  “They gonna sneak up on us?”

“Man, I don’t know,” I said. “The people would probably be curious about us, but how that would play out, I don’t know.”

“They better not fuck with us,” Devereaux said.  Christ!  All of a sudden he was a tough guy.

“Look,” I said, “they’re not cavemen.  They’re homo sapiens, just like us.  Modern humans.  As smart as we are, and presumably well adapted to living out here.  We can’t just kill them.”

“No-one’s talking about killing them, right Devereaux?” Lasher said.  “But what about the animals?  Wolf packs, or lions or what have you?”

“I honestly don’t know,” I said.  “This country is so lightly populated that most of the animals, the predators will never have seen people before.  They’d have no reason to fear us.  But we won’t be familiar to them either, so I don’t think they’ll regard us as prey.”

“Yeah,” Lasher said, “but they’re top of the line – apex predators.  They’d have no reason to fear us, right?  But maybe they’re curious.  Or really hungry.  Maybe we look like easy meals to them.  And didn’t you say there were horses here, now?  I’ll bet they’ve seen horses before, and think they’re tasty as hell.”  He stood up.  “So what I think is, we’d better be careful.  I think we’ll take watches, tonight and every night.  Wear the night vision goggles, and keep a sharp eye out. “

That actually seemed like a good idea.  All of a sudden I had visions of packs of huge dire wolves slowly sneaking up and surrounding us.   Just meat for the ravenous.

Nothing happened that night.  We took watches, and it was weird, I can tell you, sitting there, in the absolute darkness, the fire died down to only embers, no ambient light.  The stars looked low, close to the earth, brilliant, like a flung pitcher of milk.  A few clouds, scudding across the sky.  The sliver of the moon rose late. 

I heard coyotes yelping, and then, farther off, wolves. A pack, howling.  That wild and alien sound was haunting.  Jack stiffened, and I thought that he was going to chime in with their chorus. But then I heard the hoarse coughing roar of lion.  A lion!  That’s when I knew, I mean really knew, that we were someplace entirely other, some place and time wholly different from our own.  The horses stamped, restlessly, with some atavistic sense that that wild sound meant danger.  Jack’s ears pricked up, and he growled once, low in his throat.  I called him over, and he flopped down next to me, and I petted him for a while.  Just before dawn, a fox came snooping around the edges of our camp, but our scent was unfamiliar, and it didn’t come into the camp.

Dawn, clear and quite cool.  The sky at first a light, pale blue. The birdsong was loud.    Larks, thrushes, robins. Skeins of geese and other waterfowl, flying north.  Because it was, really, our first day, we celebrated at breakfast with some of the precious store of coffee we had brought with us. 

It didn’t take long to establish our routine, even though there wasn’t, really, any routine, at all.  What I mean is, we’d set out early in the morning, making our way west and a little south, stop briefly at midday, then ride on until evening, when we’d set up our camp.  But there was no routine, really, because of the terrain.  The ground here, in what would later be Missouri and eastern Kansas was rough, wild, unfamiliar.  Deadfalls, streams, rocky outcroppings – everything had to be climbed over or around.  Jack loped around, walking, trotting, sniffing the air, of course, but we kept him close to us – didn’t let him range out in front, the way he had when he’d hiked together back home.  In the mornings, before we mounted up, and at lunch, and then again, in the evenings, I’d work with him, reinforcing our bond, and improving his training.

We passed through the some light woods, and had to stop when a small herd of woods bison came through.  They seemed enormous, dark chocolate-brown, moving sedately, silently past.  Totally unafraid of us.  One bull snorted a little as he passed.  And then gone, like a dream.  Strange that animals that large could move so quietly.  No calves, yet, probably too early in the year.  I grabbed Jack’s collar, out of habit; and then decided to try an experiment.  So I let him go, and simply said “stay.”  And he stayed.  Oh, he looked at the bison as they passed, and sniffed them, and crouched down in that way that border collies have – but he stayed.

After several days of travel, the woods thinned, and the country became more savannah–like. It was our third day, when we first saw them – Mammoths.  A group of them.  The matriarch leading them, then several cows with calves.  Browsing leisurely through the trees.  They were enormous.  Brown hair, coming off in patches, chunks, streamers.  Grumbling, rumbling noises as they moved, with that slow, ponderous, implacable gait.  They seemed out-of-place.  They were out-of-place – better adapted to steppe country than to the savannah that surrounded us.  Their huge tusks were better suited to sweeping snow off covered ground, and their thick shaggy pelts were hardly necessary, at this time of year, in this climate.  Why they were this far south, I didn’t know.  They continued to browse, moving in a generally northeast direction.  I watched them for what seemed like hours, until they disappeared.  Even Devereaux seemed moved.  Until I heard him say, “Jesus, what a trophy that’d make.” 

 

A Great Big Bear

It’s got a really poor name.  Terrible, really.  The short-faced bear.  Better to call it the Plains Tyrant, or Rampaging Death, something to convey its size, power, and majesty.  Lord of the Land.  Almost anything would be a better name than the short-faced bear.

And what a bear it was. Arctodus simus is the latin name, for all you fans of nomenclature out there. Short-faced because, well, because it had a somewhat shortened muzzle.  But I’ll tell you what – you see one, you’ll know right away – instantly – that you’re looking at a bear.

A helluva big bear, too.  Listen to what Wickipedia says: “Arctodus simus may have once been Earth’s largest mammalian, terrestrial carnivore.”

Big.  Really big.  Stood six feet high at the shoulders.  For comparison, a grizzly stands about four feet high at the shoulders. Weighed up to a ton.  On its hind legs, standing, it may have been eleven feet tall.  And they’ve found its claw marks fifteen feet sbove the ground.

Arctodus simus reconstruction

Arctodus simus reconstruction (Photo credit: Wikipedia)

But it was no lumbering beast.  It had long legs, longer proportionally than modern bears.  So it was fast, too – maybe 30, 35, maybe 40 miles per hour.

And, oh yeah, it appears that it was carnivorous.  Most modern bears (not the Polar bear, though) are omnivorous – eating plants, vegetation and some meat.  But not our bear.  The short-faced bear ate meat.  Lots of it.  Based on its size, its weight, it would have needed on the order of thirty five pounds of meat per day.

Its anatomy is interesting.  Its long legs gave it speed, but its build was such that it couldn’t twist and turn rapidly, running down prey.  Some scientists think that it was a kleptoparasite, and used its speed to come up to other predator’s kills, and its size to intimidate them – the dire wolves, the saber-toothed cats, the American lion – and drive them off the kill.

I suspect that it was opportunistic, scavenging, stealing the kills of other animals, but also hunting when the opportunity arose.

Gone now.  Extinct.  Died off about eleven thousand years ago.  Why?  No one yet knows.

Humans in Europe hunted cave bears.  It seems reasonable to  suppose that early humans here hunted them, too.  But the reason why they’ve become extinct is not known. In fact, even that sentence is somewhat misleading – there may have been not one, but multiple reasons for its extinction.

Here’s are two short excerpts from my novel, which deals with the short-faced bears:

The plains were endless, treeless, windswept.  The weather continued warm and dry. The grass was short, grazed by the herds we saw. The country was not flat, but rolling, like the swell on the ocean.  And so we’d see bison grazing on a far slope, or pronghorns, or small family bands of horses. 

Saw another bear-wolf interaction, too.  We came over a rise and saw that a pack of dire wolves had brought an old bull down.  They were snarling and eating, when over the far shoulder of the rise came a bear.  On the plains, all we saw were short-faced bears.  That is what I am referring to here.  We only saw grizzlies once we were up in the mountains.  Like the one we had seen before, it was enormous, pacing at a high rate of speed.  When it saw the carcass, though, it burst into a sprint, and man, it was fast.  It charged directly at the wolves surrounding the carcass, and they fled before it, snapping and yipping. 

But they didn’t go far.  They began circling the bear, now busily eating.  They rushed its rear, snapping and feinting.  The bear was forced to turn and turn again, to keep the wolves at bay.  One wolf – dark gray – bolder than the rest ran in and snapped onto the bear’s haunch and gave that savage head-twisting yank that dogs and wolves do.  The bear snarled, whirled, and slashed with its huge paw.  And connected. Its paw only seemed to brush the wolf’s flank, but the wolf tumbled fifteen or so feet away, and lay thrashing on the ground. But the remaining wolves continued pressing in, so that the bear was whirling continuously now, unable to eat, unable to rest.  Finally, the bear broke for it, and sprinted away, with several wolves at its heels.  They chased it farther than I would have thought, disappearing up and over the rise.  But shortly, all of them returned, and rejoined the pack, now gorging on the kill.

Here’s a riddle for you science buffs out there:  Wolves don’t hibernate.  Grizzlies do. Did the short-faced bear, a plains dwelling predator, hibernate? 

*****

             “Hey!”  We both heard it at the same time.  One of our guys, calling, loudly, urgently.  We galloped the rest of the way back to camp.

            Three of them, up in the trees.  Two horses down, the rest gone, scattered.  And a bear, a short-faced bear, was eating one of the horses it had killed.

            Lasher fired just before I did, and the bear went down.  It was old.  Its muzzle was graying, and one of its canines had broken off, and its jaw was infected. Still it was impressive.  The size of these animals – all of them – the lions, the bears, the sloths, still surprised me.  They were, quite simply, unlike anything I’d ever seen in my time, in the present.

            This bear had stood six feet high at the shoulder.  Its paws were far larger than my hand.  Unlike the claws of grizzly bears, its claws were not particularly long, and were blunted, presumably because of the running and trotting it did.  It was a much faster animal, built for more speed than the grizzly.  The name “short-faced bear” is, to my way of thinking, a misnomer.  Yes, it is true, that relative to other bears, its muzzle was not as long.  But it was certainly long enough.  Its head looked exactly like what it was – the head of a large, predatory bear.  An anatomist might see one and think, “my word, that bear has a notably short face,” but I’ll tell you, what I saw was a bear, a real big bear, length of face be damned.

            It took them a little while to climb down out of the trees. 

            “What happened?” Lasher asked.

            “Man, it was quick,” Devereaux said.  “The three of us were sitting around.  Me and Whister were talking, Collins was sitting over there, when all of a sudden we heard the horses start freaking out.  Then some of them ran through camp, then that bear exploded out of the woods, and knocked two of them down, Boom! Boom! Like that, with just two swipes of his paw!

            “I’d left my rifle and pistol in the tent, like an idiot, so I yelled at everyone to climb up in the trees.”

            “Didn’t really matter much, though.  The bear wasn’t interested in us.  He went over to that one horse you saw, and started eating. Man, I didn’t think I could climb high enough!”

            Try to visualize this.  You’re looking at a bear, a big, shaggy, brown-coated bear, which even standing on all fours is as tall as you, taller when he lifts up his head, and much, much taller when he stands on his hind legs.  And standing there, on all fours, as tall as you, he’s also long, as long as your kitchen table. Long, strong legs, with paws and claws, and a muzzle with big sharp teeth.  You see, this bear is as big as a horse, maybe bigger.  This is our bear.

And he’s fast, really fast. Probably not as fast as a horse on flat level ground, but bursting out from an ambush. . . .  And then, he is massively strong.  Those paws, swung with his immense weight behind them would have no trouble knocking a horse down, and, in this case, no trouble breaking its neck.  Or two necks as it turned out.  Both horses, dead.  One eviscerated, where he’d had started eating.

            All in all, this was bad.  The bear was too big to move, as were the horses.  The carcasses would draw predators from miles around.  So even though it was now late afternoon, we would have to move.  But we had no horses – they’d run off, and were scattered.  Not good.  And, of course, we had lost two of them permanently.