If Yellowstone National Park is dangerous now, it’s a cakewalk compared to the prehistoric Pleistocene age.
Imagine a volatile thermal supervolcano simmering underfoot as mammoths, mastodons, short-faced bears, dire wolves, saber-toothed tigers and even early camels roamed the region, all competing to feed and not be food.
Lambert and Reed, both renowned researchers with advanced degrees, jointly delivered the presentation “Dire Wolves, Mammoths and Humans — Yellowstone in the Pleistocene” as part of Yellowstone Forever’s summer speaker series.
The presentation was partly prompted by the recent work of Colossal Biosciences, which aims to "de-extinct" dire wolves and wooly mammoths and possibly reintegrate them into the wild.
With super-sized predators, multi-ton herbivores, extreme weather conditions — it’s a wonder humans survived at all. And yet, the people of the Pleistocene endured to become Yellowstone’s “hyper keystone predators.”
“We are pansies compared to what we were a mere 10,000 years ago,” Lambert said. “Not only was it really cold, but Pleistocene peoples dealt with the potential threat of predation on a 24-hour basis. Fear would have been a constant reality.”
Have Land, Will Travel
Lambert, a professor of Animal Evolutionary Ecology and Conservation Biology at the University of Colorado-Boulder, discussed the animals that were living in Yellowstone during the Pleistocene, the period of Earth’s history spanning from 2.58 million years to 11,700 years ago, known to most as “the Ice Age.”
During the Pleistocene, massive glaciers covered 8% of the Earth’s surface. These glaciers were up to two miles thick and so heavy, they caused the crust underneath them to sink nearly 1,000 feet.
“I'm mentioning these statistics just to give you a sense of how this area would have been vastly different from what it is today,” she said. “The average global temperature was about 11 degrees colder than what it is today.”
With so much matter frozen in the glaciers, sea levels were much lower than they are today. That exposed a swath of land between Asia and North America, called the Beringia land bridge, which extended across present-day Alaska. The mixture of dry land and glacial ice allowed millions of animals to traverse from one continent to another.
“The Beringia land bridge was exceptionally important in the evolutionary and biogeographic history of the Northern Hemisphere,” she said. “There was a lot of faunal exchange, the movement of animal species from Eurasia into North America and vice versa.”
That’s how the Americas became infested with mammoths, bears, lions, cheetahs, and an entire menagerie of Ice Age creatures. Many of them found a perfect home in Yellowstone.
Detail of late Pleistocene life in the central West in a mural painted by Joe Venus at the College of Eastern Utah Prehistoric Museum. The animals include short-faced bears, mastodons, mammoths, saber-toothed tigers, camels and extinct musk ox. (Joe Venus, College of Eastern Utah Prehistoric Museum) 
The skeleton of an American lion at the La Brea Tar Pits in Los Angeles, California. 
Bison graze in Yellowstone National Park. (Getty Images) 
The skeleton of a Columbian mammoth at the La Brea Tar Pits in Los Angeles, California. 
A prehistoric mammoth hunt is depicted in this 1896 illustration. (Getty Images) 
Geyser Basin in Yellowstone National Park. (Getty Images) 
Portrait of a prehistoric hunter depicted in this print by Aleksei Gorodenkov. (Alamy)
Bigger, Badder, And More Of Them
Lambert wanted the audience at Yellowstone Forever to understand the enormity of Yellowstone’s Ice Age fauna. Life in the Pleistocene was on a scale that modern humanity can barely fathom.
The largest African lion can reach a body mass of around 550 pounds. The extinct American lion could reach an estimated body mass of nearly 900 pounds.
The largest grizzly on record, found in Alaska, weighed 1,600 pounds. A male Arctodus, the extinct short-faced bear, could reach a weight of over 2,000 pounds.
“Our grizzlies today are very large-bodied, although they look petite next to skeletons and skulls of the giant short-faced bear,” Lambert said. “The assemblage of Pleistocene carnivoran predators was, on average, about 47% larger in body mass than modern predators.”
Not only were predators bigger, but there were more of them. There are four species of large carnivores in modern-day North America, and six in the Serengeti of Africa. In Pleistocene North America, there were at least 12 species of large carnivores, with most of them considered “hypercarnivores,” meaning most of their diet was meat.
“Why are pronghorn so fast? The argument has been made that, up until fairly recently, they had a very fast predator pursuing them. That was the American cheetah. It’s no longer around, but we can see the vestiges of the Pleistocene past.”
There were more herbivores, too — multiple species of ground sloth, bison, over 60 species of horse, and Castoroides, the man-sized beaver.
And, of course, there were mammoths. Yellowstone was the realm of Columbian mammoths, which were considerably larger than their wooly counterparts.
“I wish I could have seen some of these amazing species running around,” Lambert said. “So, the question is, what happened?”
Clovis Crossing
As massive mammals moved across the Beringia land bridge, humans did too. That was the side of the story presented by Reed.
Reed, a software engineer turned conservationist, is involved with several conservation projects in Yellowstone. In a sense, he’s trying to amend the damage that started over 10,000 years ago when the first human reached the Greater Yellowstone Ecosystem.
Reed pointed out that one of North America's most important archeological sites is located just 60 miles north of Gardiner: the Anzick site in Park County, Montana.
“It's the oldest burial in the Americas, at roughly 13,000 years old,” he said. “It was a two-year-old boy, buried underneath a rock shelter with great care and love, sprinkling his body with red ochre. He was surrounded by carefully flaked, finished tools to take with him into the afterlife. This boy was treasured by his people.”
The Clovis are recognized as North America’s oldest human inhabitants. Although the timeline of their settlement is disputed, they had a permanent foothold across North America by the end of the Pleistocene.
Reed said there’s plenty of evidence of Clovis habitation in the Greater Yellowstone Ecosystem. Their stone tools, with the signature flute, have been found throughout Montana and Wyoming.
“They used those fluted projectiles to hunt large Ice Age mammals,” he said. “The Clovis culture remains a key marker in understanding early human migration, adaptation, and their interactions with those megafauna.”
Reed highlighted one of the latest big discoveries in Clovis research spearheaded by archaeologist Scott Dursham. A recently discovered site in the Beartooth Mountains might be the highest-elevation Clovis site ever found.
“Artifacts were found at 10,000 feet, an elevation long believed to have been buried beneath ice 13,000 years ago,” he said. “Scott's evidence suggests even the high country was at least seasonally open and occupied at the time.”
So, what were they doing there? Those are questions Reed and many others hope will be answered.
“Were they summering here? Hunting mammoths, bighorn sheep, grizzlies, or even large bison species. And if so, did they have to fight off dire wolves to protect their kill sites? This site is challenging what we thought we knew about Clovis history.”
Controversial Cause And Effect
The intersection of Lambert and Reed’s lectures was the uncertainty of what happened at the end of the Pleistocene. As prehistoric humans permanently moved into Yellowstone, its megafaunal inhabitants permanently moved out.
There are many theories about what contributed to the extinction of the massive Pleistocene mammals – climate change, disease, or (most controversially) “blitzkrieg.”
“It’s the idea of humans hunting and being really, really good at it,” Lambert said. “Megafauna extinctions occurred basically on every continent as humans showed up. This remains a huge discussion, but there are waves of extinction after the arrival of humans to areas where they had not previously been.”
Reed showcased the archaeological evidence of a technological revolution in North America during the same period when mammoths, lions, and cheetahs were declining. He brought several of those tools, real and replica, to the presentation.
According to Reed, humans had been “throwing sticks at birds” for 300,000 years before reaching North America. He called this “the iRock technology zone.”
Evidence collected from Clovis sites across North America shows that humanity had reached “iRock Level 7” with the atlatl, a device for throwing spears with a sharpened rock at the end. As technology improved, their arsenal grew.
“After the Clovis arrived, stone tools exploded in a diversity of sizes, shapes, and functions,” he said. “For 11,000 years, people in Yellowstone were throwing an atlatl to kill animals.”
Reed also believes the Clovis were learning from the other apex predators in their neighborhood. He showed a video of wolves killing an elk by chasing it off a cliff, a strategy used to kill everything from mammoths to bison for thousands of years.
“Early people may have picked up hunting strategies just by observing predators,” he said. “We know Native Americans used similar tactics to drive bison off cliffs. They may have learned it from wolves, here in the New World or the Old World. And they didn't hunt alone. They likely used their own wolves, domesticated into dogs, as hunting partners.”
Jeff Reed demonstrates the workings of the atlatl, one of the most potent weapons used by the Clovis culture. This weapon would have been used to hunt the massive mammoths, bison, and other megafauna of the Pleistocene, and might have helped drive them to extinction. (Andrew Rossi, Cowboy State Daily) 
Jeff Reed, technologist and conservationist, shows several tools used by the Clovis and other indigenous cultures that lived in Yellowstone National Park. When the Clovis arrived in North America, they underwent a technological revolution in the diversity of their stone tools, used to hunt the massive mammals that roamed Yellowstone during the Pleistocene. (Andrew Rossi, Cowboy State Daily) 
Joanna Lambert, a professor at the University of Colorado-Boulder, discusses the ecological changes between the Pleistocene and the modern world. The megafaunal denizens of Yellowstone were not only bigger than their modern-day counterparts, but were also more diversified and adapted for a harsh, cold climate. (Andrew Rossi, Cowboy State Daily) 
Joanna Lambert with a reconstruction of an American cheetah hunting a pronghorn. Cheetahs were among the many mammalian species that disappeared at the end of the Pleistocene, which curiously coincided with the arrival of humans in North America. (Andrew Rossi, Cowboy State Daily)
Bring ’Em Back Alive?
As the presentation concluded, the question-and-answer session quickly turned to the dire wolf in the room. Colossal Biosciences recently unveiled a pair of “resurrected” dire wolf cubs, incorporating DNA from the skulls of the long-extinct predators.
Lambert, who’s on Colossal’s scientific advisory board, said Colossal was “an interesting entity” with “a really interesting backstory.” She cited the cutting-edge technology used to create the “dire wolves,” but also kept the reality of the accomplishment in perspective.
“One thing's for sure - those bits and pieces of the dire wolf genome are doing something now,” she said. “In that sense, those molecules are de-extinct, but we don't have dire wolves running around because of it.”
Lambert also commented on the “de-extinction” of an apex predator that might not have been driven to extinction by prehistoric humans. She believes there may be an ecological case for the wooly mammoth's de-extinction (which Colossal aims to do by 2028), but didn’t see the same precedent for the dire wolf.
Clovis probably found and learned to live alongside dire wolves 10,000 years ago, but there is no place for them today. Yellowstone has evolved beyond the dire wolf.
“Yellowstone has changed fantastically since the Pleistocene,” she said. “Huge shifts in climate and vegetation, and a complete reassembly of the food web. We wouldn’t be putting the dire wolf back into the Upper Pleistocene. It would be utter chaos.”
Reed agreed and voiced his opinion of what Colossal should focus on, “de-extincting.”
“I want them to bring back the giant beaver,” he said. “It's crazy. Bring back the giant beaver, Colossal!”
Hyper Keystone Predators
Lambert and Reed emphasized that life in Yellowstone was no picnic for humanity at the end of the Pleistocene. And yet, they persisted.
Early humans like the Clovis survived and triumphed in a world dominated by several apex predators larger than any mammalian predators alive today. They established a new hierarchy with humans, according to Lambert, as “hyper keystone predators.”
“We are the only species that kills other apex predators,” she said. “As a single species, we account for the mass extirpation of apex predators around the globe, and we've been doing this for a very long time.”
This can be seen as a testament to humanity's tenacity and adaptability. But Lambert and Reed commented on what we’ve lost since our competition abandoned the competition.
“The upshot of life in a cold, very harsh landscape with megafauna and abundant predator assemblages is that it was extremely difficult,” she said. “We are pansies compared to what we were a mere 10,000 years ago. Fear would have been this constant reality. But we cannot be scared all the time. We cannot live in a constant state of fight or flight.”
Using knowledge, memory, and tools, humans learned to live with the lions, wolves, and short-faced bears until they outlasted them. In our “victory,” Lambert said humanity has forgotten how to co-exist with our fellow predators.
“The folks living in Yellowstone would have extremely rich knowledge of how to hunt, where to avoid predators, etc,” she said. “They would have been habituated to knowing that there were other predators and large-bodied mammals around and had the knowledge of what the heck to do about it. All of that is lost now.”
Reed highlighted a map of all the roads in the United States and how the Greater Yellowstone Ecosystem is one of the last roadless places in the nation. He cited a quote from the opening of “The Lord of the Rings: The Fellowship of the Ring” to emphasize that point: “Much that once was is lost, for none now live who remember it.”
“Many of us today have lost our ancestors' knowledge of wild places, and the intelligence of animals and plants around us,” he said. “Yellowstone is a very special place. Cherish it. Protect it. Fight for it. Use this knowledge to inspire conservation efforts, and take inspiration from the Clovis and other people who were here.”
Andrew Rossi can be reached at arossi@cowboystatedaily.com.
