One sunny June morning in western Wyoming, a walk into the sagebrush revealed a remarkable sight: two pronghorn fawns, startled from near my feet, exploded into motion. Their spindly legs churned as they sprinted away, a blur of motion disappearing across the vast landscape at astonishing speed. These young animals, if they survive to adulthood, will join the ranks of Earth’s fastest land creatures. Pronghorn, slightly smaller than deer, possess the incredible stamina to cover seven miles in just ten minutes, capable of reaching nearly 60 miles per hour in short bursts, outrunning even horses and wolves. Their elongated legs, combined with oversized hearts and lungs, are perfectly adapted for navigating the expansive sagebrush basins of Wyoming, their ancestral home for tens of thousands of years. Here, they have historically thrived, browsing on shrubs and evading predators.

However, the modern pronghorn faces challenges far beyond its evolutionary past. Their world is increasingly crisscrossed by rural housing developments, energy infrastructure, fences, and highways, leading to significant habitat fragmentation. Furthermore, the Western landscape they inhabit is already considerably warmer than the ancient environment in which they evolved, and this warming trend is accelerating annually. The familiar world of pronghorn, the world where the author grew up and is now raising children, is undergoing rapid transformation. Droughts are becoming more frequent, winters less snowy, and spring thaws arrive earlier, leading to diminished stream flows by late summer. The region experiences fewer frost days, hotter summers, and more intense storms. These shifts in temperature and precipitation patterns are causing conifer forests to dry out, burn, and die, while invasive, fire-adapted grasses are encroaching on rangelands. In 2024 alone, over 1,300 square miles of Wyoming burned, more than double the area affected in recent major fire years, a stark indicator of escalating wildfire risk. These environmental changes are profoundly impacting wildlife, including the pronghorn.

Consider the plight of pronghorn in northeastern Wyoming’s Powder River Basin, a sprawling expanse of grassland and shrub-covered bluffs stretching over 100 miles. When lightning ignited a fire on its western edge in August 2024, high winds fanned the flames into a destructive inferno that consumed hundreds of square miles within a single day. After evacuation orders were lifted, ranchers returned to find landscapes deeply etched into their lives scorched beyond recognition. As the charred earth cooled, wildlife managers and landowners discovered the tragic toll: at least 70 dead and dying pronghorn, some found near fences, others succumbing in the open where the fire had overtaken them. North America’s swiftest land animal proved unable to outrun the devastating flames.

The images of these deceased Wyoming pronghorn and the vast, blackened landscape resonated deeply, prompting reflection on the future world my children will inherit. In September 2018, the author’s first child was brought home from the hospital under skies stained a hazy orange by lingering wildfire smoke. While the precise appearance of this landscape decades from now remains unpredictable, its transformation is undeniable, and my children will undoubtedly grow up in a world vastly different from the one generations have known.

This is not the first climatic upheaval pronghorn have weathered. Their earliest North American ancestors appeared in the fossil record during the Miocene epoch, approximately 20 million years ago, a period when the planet was significantly warmer than it is today. Modern pronghorn evolved later, during the colder ice ages. Around 12,000 years ago, as the ice ages concluded and North America experienced a sudden warming trend, most large mammal species went extinct. Yet, the pronghorn persisted, adapting to the new environmental conditions.

Researchers suggest that climate change may precipitate "state shifts," wherein entire ecological systems, such as pine forests or sagebrush steppe, transform into entirely different entities. The crucial question arises: will pronghorn successfully navigate this new era of climate-driven changes, much as they did 12,000 years ago? And will humanity? The ancestors of those twin fawns, who sprang away so suddenly, may hold clues to answering these profound questions. By understanding how pronghorn historically survived such dramatic shifts, we might glean invaluable insights into how their descendants, and indeed our own species, can adapt to an uncertain future.

During spring snowstorms in southeastern Wyoming, groups of pronghorn are often observed near town edges, by the airport, or resting beyond the highway right-of-way fences, their gaze peering through the swirling snow. They are undertaking their annual migration from wintering grounds to the more verdant summer fawning areas, likely located in the foothills. With their large eyes and distinctive, antenna-like horns, pronghorn possess an almost alien appearance. However, they are not creatures from another realm, but rather living relics from a bygone era, survivors of the once-vast assemblage of unique, now-extinct animals that roamed the icy, windswept basins of ancient North America. This historical context fuels a desire to understand the climate, flora, and fauna of those distant times.

On the second floor of the University of Wyoming Geological Museum, a striking 10-foot-wide mural vividly portrays the Laramie Valley during the Pleistocene epoch, a period of ice ages spanning from approximately 2.58 million to 11,700 years ago. The artwork, offering a view toward the mountains from a bluff overlooking present-day Laramie, depicts a muscular saber-toothed cat snarling at a colossal bison with spear-like horns. Nearby, three mammoths, adorned with curved ivory tusks and thick fur, observe warily. The landscape is carpeted with low-lying scrubby plants, and the Laramie River is fringed with willows. In the distance, glaciers descend the drainages of the treeless Medicine Bow Mountains, their familiar rocky peaks piercing the sky above a mantle of deep ice and snow.

In a nearby university building, paleoclimatologist Bryan Shuman was settling into his new office, surrounded by stacks of books and papers, each layer a repository of past narratives. A professor in the UW Geology and Geophysics Department, Shuman meticulously reconstructs ancient hydrological, climatic, and ecological conditions by examining microscopic particles within lakebed sediment cores and mapping ancient lake shorelines, delving as far back as the late Pleistocene. Laramie is renowned for its cold climate, but the Pleistocene Laramie was even more severe. Shuman’s research indicates that in the Central Rockies, home to over a third of the world’s pronghorn population today, average annual temperatures during the coldest Pleistocene periods were as much as 18 degrees Fahrenheit lower than current levels. This extreme cold fostered permafrost, creating wedge-shaped patterns in the ground that are still visible on the outskirts of town.

The mural’s depiction of ice and plant cover aligns with scientific findings. "We know glaciers were much more extensive," Shuman confirmed, pointing to "very clear geomorphic evidence where the glaciers were." Trees were scarce in that frigid environment. Shuman presented a graph illustrating temperature fluctuations over thousands of years alongside pollen data extracted from sediment layers. "You can see when it was really cold, it was mostly a grass- and sagebrush-dominated landscape," he explained. Pollen analysis also revealed the presence of willows, likely akin to the low, shrubby varieties found in the Arctic today. The landscape was also considerably drier than it is now. Shuman employs ground-penetrating radar to map ancient lake shorelines, providing insights into past aridity. "We are living in an unusually wet time," he stated. "This is probably the wettest time in the last 20,000 years, at least," for the region.

The late Pleistocene was also characterized by strong winds and a "really dusty" environment, according to Shuman. Glacial meltwater carried pulverized rock sediment, which, upon drying, was dispersed by the wind. These Pleistocene winds sculpted hollows across Wyoming, formed dunes in the Great Plains, and deposited thick layers of glacial dust extending hundreds of miles into the Midwest. The author attempts to visualize pronghorn, similar to those enduring modern snowstorms, traversing an ancient landscape that was colder, drier, windier, and dustier than today’s.

During the Pleistocene, pronghorn faced threats beyond the elements. Fossil evidence reveals that even in that harsh environment, several formidable predators roamed Wyoming. These included Miracinonyx, the American cheetah, a 160-pound relative of the mountain lion with long legs adapted for chasing prey. The formidable American lion, one of the largest cats to ever exist, weighing up to 1,000 pounds, and the powerful Beringian wolf with its robust jaws and large teeth, also hunted pronghorn. Isotopic analysis of their fossils confirms that all three species preyed on pronghorn.

The remarkable preservation of these ancient creatures is due to Natural Trap Cave, a vertical, bell-shaped cavern on the western slopes of the Bighorn Mountains in northern Wyoming. Its opening, an oval hole about 15 feet across, has served as a fatal trap for millennia. Animals stumbling into the opening would fall more than 80 feet into the cave, where they would perish from injuries or starvation. With no access for scavengers, complete skeletons remained undisturbed, preserved by the cave’s constant 42-degree Fahrenheit temperature, which maintains both DNA and bone integrity.

Julie Meachen, a vertebrate paleontologist from Des Moines University, has led a research team at Natural Trap Cave since 2014. During her initial field season, she navigated a rough four-wheel-drive road to reach the cave, where an experienced caver had established a rope system. "I was a little intimidated by rappelling in 80 feet," she confessed, noting her prior lack of such experience. As Meachen descended into the cavern’s maw, she observed bones protruding from the walls. While researchers in the 1970s and 1980s had unearthed remains of camels, cheetahs, horses, and even mammoths, the cave had remained unexplored for decades. "We just knew that it was a treasure trove of fossils," she remarked.

Alongside the bones of Pleistocene lions, wolves, and bears, paleontologists in earlier expeditions discovered pronghorn remains dating between 17,000 and 20,000 years old, virtually indistinguishable from their modern counterparts. The cave also yielded evidence of at least 14 other large mammal species, including modern bighorn sheep and coyotes, extinct Pleistocene herbivores resembling stilt-legged horses, musk oxen, and camels, and even giant short-faced bears, more than double the size of contemporary grizzlies. This past summer, Meachen’s team recovered a mammoth scapula, ribs, and several vertebrae, with the skull potentially still buried. These bones belong to at least three mammoths that fell into the cave during the Pleistocene, Meachen stated.

Todd Surovell, an archaeologist at the University of Wyoming specializing in hunter-gatherers, has conducted research at mammoth dig sites in Wyoming and published on late-Pleistocene extinctions. During a visit to his campus office, he shared a small Ziploc bag containing a walnut-sized shard of mammoth ivory, smooth and creamy white with jagged brown ripples. While this particular piece was from Alaska, Surovell noted the prevalence of Columbian mammoths in Wyoming. These giants, the largest mammoth species in the Americas, ranged from Canada to Mexico along the front of the Rockies. "Just tons of mammoths," Surovell commented. The author conjures an image of a 22,000-pound behemoth using its trunk to grasp tussocks of grass, its 16-foot tusks sweeping through the air, while pronghorn cautiously navigated the terrain, ever vigilant for lurking lions and bears. Such scenes played out for millennia until an unknown force drove most of these magnificent creatures to extinction.

On a geological timescale, the 7,000-year transition from the frigid ice age to the Holocene, the current epoch, occurred with remarkable swiftness. However, for the pronghorn, these environmental shifts unfolded over hundreds of generations. Around 17,000 years ago, the Earth’s axial tilt, which wobbles on a 41,000-year cycle, began to increase, allowing more summer solar radiation to reach the planet. This triggered the melting of ice caps. As reflective white ice retreated towards the poles, darker ground surfaces absorbed more solar heat. Shuman, the paleoclimatologist, directed the author to a textbook, Earth’s Climate: Past and Future, which was studied intensely to comprehend the end-Pleistocene warming and its scientific investigation.

The melting ice caps released vast quantities of freshwater into the oceans, carrying sediment and dust, and ultimately causing sea levels to rise by approximately 360 feet. These immense freshwater inflows altered ocean currents and warmed the oceans, leading to the release of carbon dioxide. The resulting increase in atmospheric carbon dioxide intensified the greenhouse effect, trapping solar heat and driving further warming. Shuman explained, "This chain of orbital changes, ice sheet changes, dust and ocean changes, all causes carbon dioxide to go up and down." Carbon dioxide, he added, "is probably the biggest single hammer on the system."

By approximately 10,000 years ago, atmospheric carbon dioxide levels had risen by over 40%, leading to a global temperature increase of 7 to 11 degrees Fahrenheit. The central regions of North America became wetter, transforming arid grasslands into lusher environments and allowing forests to expand northward. Pollen records indicate the flourishing of pine, spruce, and fir trees. However, this botanical shift was not universally beneficial for the megafauna. "A lot of the big things that used to be here just didn’t survive," Meachen observed.

Of the numerous large mammals inhabiting Pleistocene North America, at least 59, and possibly more, became extinct, with only 26 species remaining today. One analysis suggests that 72% of large mammal species vanished from the continent, encompassing everything from horses, mammoths, and giant beavers to ground sloths, along with many predators. "The bigger you are, the more likely you are to go extinct," Surovell noted. "Very few small things go extinct." An analysis he co-authored in 2009 indicated that these extinctions likely occurred rapidly, between 13,800 and 11,400 years ago – a mere blink of an eye in geological terms. He stated that subsequent evidence has only strengthened this conclusion.

The simultaneous extinction of so many large land mammals remains a profound mystery, a subject of ongoing debate and investigation. Scholars continue to explore various contributing factors, including human influence, a potential asteroid impact, or interspecies disease transmission. However, scientists generally concur that abrupt climate change played a pivotal role in driving this significant loss of biodiversity.

Among the survivors of these past extinctions, the pronghorn antelope stands out as one of the continent’s most enduring species. Antilocaprids have inhabited North America for more than four times as long as cervids (deer, elk, moose, and caribou), whose ancestors arrived around 4.8 million years ago. The ancestors of modern bovids (bison, bighorn sheep, mountain goats) appeared a mere 2.5 million years ago. Modern pronghorn, the sole living descendant of the original Antilocaprids, are unique to North America, having evolved to thrive in this specific environment. "In fact, they were survivors," stated Christine Janis, professor emerita of ecology and evolutionary biology at Brown University, whose research focuses on animal evolution in relation to climate change over the past 20 million years. She noted that the pronghorn’s ancestors navigated earlier extinctions of ancient deer-like animals around 5 million years ago, "They survived along with things like horses and camels until all these guys went extinct at the end of the Pleistocene."

The precise mechanisms by which pronghorn achieved this remarkable survival remain elusive, yet several theories have emerged. Meachen pointed to their ability to subsist on minimal water. "They were able to eat dry, scrubby vegetation that other big herbivores, like horses and bison, were not able to eat and make use of, and they were able to do that and have less water stress than other animals," she explained. Surovell added a pragmatic observation: "You know, another thing that they probably benefited from was the extinction of the American cheetah." Janis attributed their success to their high-crowned teeth, which allowed them to graze on low-growing, gritty browse. These teeth, extending well above the gumline, possess ample surface area to wear down gradually, even with a lifetime of chewing dusty Pleistocene vegetation. She also highlighted their small size, which facilitates a faster reproductive rate compared to larger animals. While a massive camel or mammoth might produce a single calf every few years, pronghorn typically give birth to two fawns each spring. Janis summarized the key to pronghorn survival succinctly: "Be small and be adaptable in your diet. That’s a good way to survive."

Pronghorn have demonstrated an extraordinary capacity for adaptation throughout their history, and further challenges lie ahead. Earth’s surface temperatures consistently set new records annually, pushing the boundaries of climate change. The greenhouse gases being released into the atmosphere today are projected to drive global average temperatures to shift at a rate far exceeding the 7,000-year transition that marked the end of the ice ages, melted ice sheets, thawed permafrost and glaciers, and transformed tundra into forests, leading to the extinction of numerous large mammals. "That’s the type of magnitude change we’re talking about," Shuman remarked, "except it’s going to keep going into a warmer direction that’s still hard to imagine."

The future feels precarious, both for pronghorn and for humanity. Planetary changes are unfolding at a pace potentially unseen since the asteroid impact that wiped out the dinosaurs approximately 66 million years ago. Can our own living systems adapt to such rapid and profound transformations? As an inhabitant of this land and a mother of two young Wyoming natives, contemplating this question is almost unbearable. Yet, studying the resilience of pronghorn has offered a shift in perspective. The author expresses gratitude for not having lived through the arid, treeless, intensely cold conditions of the deepest ice ages. It is acknowledged that increased precipitation in some areas has historically supported the growth of forests and benefited certain species, including pronghorn, in warmer modern climates. The Earth’s dynamic nature, sustaining life through billions of years and diverse climates – from periods warm enough for palm trees and crocodiles in Wyoming to millennia of ice and snow, and back again – is a source of wonder. The planet’s living systems exhibit a remarkable capacity for continuous adjustment. It is recognized that, more readily than most animals, human children can adapt their diets and, much like pronghorn, thrive in a variety of climates and environments, even migrating to new habitats if necessary.

When the wildfire scorched nearly 275 square miles of Wyoming’s Powder River Basin in 2024, the 70 pronghorn that perished represented a fraction of the tens of thousands of survivors in the region. These survivors birthed new fawns and found sustenance in the fresh green grass that emerged in the burned areas the following spring. Perhaps the enduring lesson from pronghorn is not to dwell on the past or anxiously anticipate the unknown future, but rather to engage with the present moment with heightened awareness and gentle attention, discerning subtle shifts in the wind and the scents carried upon it. Pronghorn embody the wisdom of deeply understanding one’s home habitat and aligning personal patterns and behaviors with the forces of the land. They urge a keen observation of how snow drifts, a recognition of which plants emerge after a soaking thunderstorm, and an understanding that each spring will uniquely unfold. They teach the importance of passing on knowledge to children, fostering their ability to identify birdsong, comprehend the seasonal movements of animals, breathe deeply, and continue moving forward with feet firmly planted on the Earth.