Paleontologist Ken Rose examines the fossilized jaw and some teeth of a Coryphadon, an extinct, galumphing, cow-sized herbivore from the Eocene. Four decades of work in the Bighorn Basin gives the fossil-hunting professor insight about what happens on earth when the climate changes. (Angus M. Thuermer Jr./WyoFile — click to enlarge)

Bighorn Basin fossils could teach about climate change

By Angus M. Thuermer Jr.
— July 29, 2014

Fossil hunter Ken Rose pauses during a stifling day in the BLM badlands west of Worland to take in the variegated sunbaked cliffs eroding around him.

Ancient bones found in the purple, green and red ravines, gullies and hoodoos that mark the Bighorn Basin drew him here. Underfoot lies the fossiliferous Willwood formation, 2,300 feet of sandstone, claystone and shale laid down in alluvial floodplains more than 50 million years ago.

Even though the northern Wyoming BLM desert is the sun’s anvil, the professor from Johns Hopkins School of Medicine is out in the noonday sun, pecking at rugosities with an ice pick, hoping for another discovery in a land he’s haunted for 45 years.

“This looks delightful,” he says of the moonscape around him. “There should be little jaws on here or something.”

When he finds some fossilized teeth — smaller than a fingernail — he pauses to marvel. “Nobody’s seen this thing in 55 million years,” he says.

Rose’s vision, acute as it is looking back, isn’t focused on the past. The Eocene epoch he studies began with a nine-to-14-degrees Fahrenheit spike in temperature. The climate is changing much faster today.

“The increase in temperature probably occurred in 25,000 to 50,000 years,” Rose said. “We’re doing this in 50 to 100 years. At the rate we’re going, we’ll reach the same kind of increase in temperatures in one-tenth the time.”

The implications loom, Rose says. “We’re in the middle of the sixth great extinction on Earth. It probably won’t take too long for humans to go extinct.”

Wild horses, past and present

The crew of fossil hunters takes off into Paradise Alley west of Worland for a day of searching in the badlands. The 100-mile-long Bighorn Basin is the best place in the world to find Eocene-epoch fossils, in part because of exposed, un-vegetated slopes. (Angus M. Thuermer Jr./WyoFile — click to enlarge)

The lesson also is apparent to paleontologist Amy Chew, one of Rose’s crew, who found part of a fossilized jaw from a miniature horse, Hyracotherium. The structure of its teeth reveal that it chewed on leaves and fruits from a tropical forest. Its little legs enabled it to gallop away from bizarre-looking predators.

The prehistoric pony’s mobility also allowed it to migrate from the Bighorn Basin as the environment of the Eocene epoch changed.

Only by moving to a friendlier place could the horse and its cousins evolve into the wild Spanish mustangs Chew passed on her way to the fossil bed that morning.

“The question is, ‘What happens to the environment and how do the animals respond to that,’” said Chew, an associate professor at Western University of Health Sciences in Pomona, California. Part of the answer is that Hyracotherium went extinct in the Bighorn Basin.

The paleontologist’s pursuit, however, reaches further than the arcane world of bone-hunting academics and its withering vocabulary.

“How can we understand modern animals and their ecosystems,” Chew said, “if we don’t understand their history?”

The Hopkins’ crew — about eight depending on who’s in camp — searches fossil beds that formed right after dinosaurs went extinct. It was the beginning of the age of mammals, including primates.

During the early Eocene, mammals may not have had to worry about flesh-ripping dinosaurs. But the heat …

Tropical forests grew as far north as the arctic. There were no freezing temperatures, no polar ice caps. The epoch had several warm periods, unsettling the order of things.

Amy Chew scours a slope for fossils, some of which are smaller than a fingernail. Within yards of this spot, she found and collected a set of fossilized teeth some 50 million years old. (Angus M. Thuermer Jr./WyoFile — click to enlarge)

Some fossils that appeared in a layer of sand dating from before climate changes can’t be found in layers from later dates. Some that weren’t there before start appearing later.

“You can look all you want,” Rose said, but the conclusion is inevitable. Species in the Bighorn Basin went extinct or migrated.

“The ability of species to adapt as quickly as climate change — it won’t happen,” he said.

Rose pointed to the distant Bighorn Mountains, where pikas are becoming rare, to illustrate the effects of warming today. The temperature-sensitive rock-pile dwellers “have moved as high as they could get,” to escape the heat, yet it still pursues them.

“They’ll probably become extinct,” as will other species, Rose said. “It’s almost certain there will be loss of big game.”

Sometimes warming can increase rainfall or precipitation, Chew said. “That’s probably not what’s in store for us.”

When the temperature shot up at the start of the Eocene, “The impact on the environment was to become arid,” Chew said. “There’s drying … everything gets very dry.”

The historical record lends Rose a grim forecast. The planet has a carrying capacity of perhaps 12 billion people, a population today of 7 ½ billion.

“There’s not going to be any natural environment left,” he said. “The lemurs – many of them are disappearing. There are extinctions of primates in South America. We’re squeezing them into smaller and smaller areas.

“Most people don’t care,” Rose said. “It’s sad.”

Against a backdrop of the Willwood formation, Rose searches for fossils from the Eocene epoch, when mammals proliferated across the globe. Rapidly warming temperatures during the period give insight about what might happen today because of climate change. (Angus M. Thuermer Jr./WyoFile — click to enlarge)

Rare exposure

It took 20 million years to lay down the geologic strata of the Eocene and nowhere is the geology of the epoch more available than across the 100-mile long Bighorn Basin. There’s lots of un-vegetated scarps, slopes and flats.

“To many, they’re badlands,” he said of his hunting grounds. To paleontologists, “they’re the richest Eocene exposures in the world.”

Chew holds fragmets of a fossilized bone she discovered last week. The Bighorn Basin has been studied for more than 100 years, making it the best-documented area for Eocene mammal fossils in the world.

All manner of mammal fossils are present. In addition to the bones of small horses, there are fossils from deer-like creatures, lemur-like primates, things that looked like tapirs.

Scientist can only guess at the shape and look of other inhabitants. Last year, Rose chipped out part of the lower jaw of a Coryphadon. He can only describe it as a galumphing cow-sized herbivore that has no relationship to modern mammals.

You can’t find Eocene fossils everywhere. “In Europe, they look for a pile of stones,” Rose said of the few Eocene beds. “It’s on the edge of someone’s vineyard. And they work it ‘til it’s gone.”

The “phenomenal” Bighorn is “the best-documented stratigraphic section of vertebrate fauna in the world,” he said. “There is no single basin like that that preserves such a dense and continuous record of life for three to four million years.”

Outdoor classroom

The outdoor classroom provides an opportunity, said Heather Kristjanson, an inquisitive 23-year-old in the second year of her anatomy Ph.D program at John Hopkins. She’s come for a couple of summers to comb the desert in 100-degree heat.

“Worland and the rest of Wyoming has an opportunity to come out here and see what’s being done,” she said. “I think it would be great if [students] all had a field trip out here once a year.

“Wyoming could easily have some small little piece in their science class [that says] ‘By the way, we have this excellent record,’” She said. “It should be brought up.”

Yet the discoveries in the heart of Wyoming are — technically speaking — off limits to its students. Legislators and Gov. Matt Mead earlier this year blocked the adoption of Next Generation Science Standards, which would require that students have an understanding of evolution, among other things.

The banned standard would require middle school students to “analyze and interpret data for patterns in the fossil record that document the existence, diversity, extinction, and change of life forms throughout the history of life on Earth under the assumption that the natural laws operate today as in the past.”

The prohibition baffles Kristjanson. “They’re just denying education to kids,” she said. “You’re purposefully putting them at a disadvantage. That’s wrong.” When she has kids, “I’d want them to learn evolution as much as they could.”

Sorting and cataloging of the day’s finds takes place in a trailer that’s stored in Worland over the winter. All manner of fossil hunters and their kin drop by the Johns Hopkins expedition camp during the few summer weeks the crew is camped along Fifteenmile Creek. (Angus M. Thuermer Jr./WyoFile — click to enlarge)

Fossil hunter Rachel Dunn, an assistant professor at Des Moines University in Iowa, agreed.

“It’s a little bit ridiculous,” she said of the legislative machinations. “The animals within [the Bighorn Basin] show us Darwinian evolution in action.

“The foundation of the medical world follows Darwin,” Dunn said. “If we ignore that, we’re basically going backwards. The rest of the world would outpace us.”

If lawmakers would deny science to some, perhaps they should eschew it themselves, she said. “The people who don’t want to teach evolution in school should stop taking antibiotics.”

Wyoming might be robbing itself of talent too. If offered a job in Wyoming, Dunn, a prospective mother who’s in her mid 30s, wouldn’t jump.

“I would have to think two or three times about it,” she said. “It would have to be a really good gig to get me here.If my kids weren’t going to get [evolution] in school, it would be enough to stop me from moving here.”

Angus M. Thuermer Jr. is the natural resources reporter for WyoFile. He began working at the Jackson Hole News in 1978, and was editor of the Jackson Hole News and Jackson Hole News&Guide before joining WyoFile. Contact him at or (307) 690-5586. Follow him @AngusThuermer.

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Angus M. Thuermer Jr.

Angus M. Thuermer Jr. is the natural resources reporter for WyoFile. He is a veteran Wyoming reporter and editor with more than 35 years experience in Wyoming. Contact him at or (307)...

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