One sunny June morning, a walk through the sagebrush of western Wyoming led to an unexpected encounter: two pronghorn fawns, spindly legs a blur, sprinted from beneath my feet and vanished into the vastness of the landscape. These young animals, if they survive to adulthood, will join the ranks of Earth’s fastest land mammals, capable of bursts approaching 60 miles per hour, a speed far exceeding that of horses or wolves. Their lithe build, oversized hearts, and powerful lungs are perfectly suited for the expansive sagebrush basins of Wyoming, their ancestral home for tens of thousands of years, where they have navigated a world of open spaces, nibbled shrubs, and evaded predators. Today, however, their survival depends on their ability to traverse a landscape increasingly crisscrossed by rural housing, energy development, fences, and highways, all while confronting an environment that is already significantly warmer than the one in which they evolved, and which continues to grow hotter each year.

The world that pronghorn have long inhabited, the world where generations have lived and raised children, is undergoing rapid transformation. Droughts have become more frequent and severe, winters less snowy, and the spring melt arrives earlier, leading to diminished streamflows by late summer. The region is experiencing fewer frost days, hotter summers, and more intense storms. These shifting climatic patterns are causing conifer forests to dry out, burn, and die, while invasive, fire-adapted grasses are encroaching upon the rangelands. In 2024 alone, over 1,300 square miles of Wyoming burned, more than double the acreage of other recent significant fire years, and pronghorn are feeling the impact of these changes acutely.

Consider the pronghorn in northeastern Wyoming’s Powder River Basin, a vast expanse of grass and shrub-covered bluffs stretching over 100 miles. When lightning ignited a fire on its western edge in August 2024, high winds fueled the flames into a conflagration that consumed hundreds of square miles within a single day. Ranchers returning after evacuation orders found familiar landscapes scorched beyond recognition. As the burned earth cooled, wildlife managers and landowners discovered at least 70 dead and dying pronghorn, some found near fences, others overtaken in the open by the relentless advance of the fire. The pronghorn, North America’s fastest land animal, proved unable to outrun the inferno.

Witnessing the images of charred earth and the plight of these Wyoming pronghorn evoked a profound concern for the future environment my own children will inherit. I recall bringing my first child home from the hospital in September 2018 under skies stained a hazy orange from lingering wildfire smoke. While the precise appearance of this landscape decades from now remains uncertain, one thing is clear: it will not be the same as the world we have known for generations. My children are poised to grow up in an era fundamentally different from the one their ancestors experienced.

This climatic upheaval is not the first that pronghorn have faced. Their earliest North American ancestors appeared in the fossil record approximately 20 million years ago, during the Miocene epoch, a period when the planet was generally warmer than it is today. The modern pronghorn evolved later, during the much colder ice ages. When these ice ages concluded around 12,000 years ago and North America experienced a rapid warming trend, most large mammal species disappeared. However, the pronghorn persisted, demonstrating a remarkable capacity for adaptation to the new conditions.

Scientists suggest that climate change may precipitate "state shifts," leading to the transformation of entire ecological systems, such as a pine forest giving way to a different biome. The crucial question remains: will pronghorn, as they did 12,000 years ago, successfully navigate this new set of climate-driven challenges? And will humanity?

Perhaps the ancestors of the very fawns that startled me that June day hold clues to these pressing questions. By understanding how pronghorn historically weathered environmental changes, we might glean insights into how their descendants, and indeed our own species, can adapt to an uncertain future.

When spring snowstorms sweep across southeast Wyoming, herds of pronghorn are often observed near the edge of towns, seeking refuge beyond the highway right-of-way fences as they migrate from their wintering grounds towards the more verdant summer fawning areas, likely in the mountain foothills. With their large eyes and distinctive, antenna-like horns, pronghorn possess an almost alien appearance. Yet, they are not creatures from another world but rather living relics from another time, survivors of the vast assembly of now-extinct megafauna that once roamed the windswept, icy basins of North America. This history prompted a deeper exploration into the climate, flora, and fauna of those ancient eras.

On the second floor of the University of Wyoming Geological Museum, a striking mural depicts the Laramie Valley during the Pleistocene epoch, a period characterized by a series of ice ages spanning from 2.58 million to 11,700 years ago. The artwork portrays a view from a bluff overlooking what is now the author’s hometown, with a muscular saber-toothed cat snarling at a massive bison sporting spear-like horns. Nearby, three mammoths, their curved tusks and heavy fur robes rendered with detail, observe warily. The landscape is dotted with scrubby plants, and a fringe of willows lines the Laramie River. In the distance, glaciers descend the drainages of the treeless Medicine Bow Mountains, their familiar rocky peaks jutting above deep snow and ice.

Paleoclimatologist Bryan Shuman, a professor in the UW Geology and Geophysics Department, was encountered in a nearby university building, where he was settling into a new office filled with boxes of books and papers, each layer holding stories of the past. Shuman’s research focuses on microscopic particles extracted from lakebed sediment cores and the mapping of ancient lake shores, allowing him to reconstruct the hydrology, climates, and ecologies of environments dating back to the late Pleistocene. His work reveals that Laramie, known for its cold temperatures today, was significantly colder during the Pleistocene. In the Central Rockies, a region inhabited by over a third of the world’s pronghorn population, average year-round temperatures during the coldest Pleistocene periods were as much as 18 degrees Fahrenheit lower than present-day averages. This extreme cold created permafrost, forming distinctive polygon-shaped patterns on the ground, still visible in areas surrounding the city.

The mural’s depiction of ice and plant cover aligns with scientific understanding. "We know glaciers were much more extensive," Shuman confirmed, citing clear geomorphic evidence of their former reach. The frigid environment supported limited tree growth. Shuman presented a graph illustrating temperature fluctuations over thousands of years alongside pollen analysis from lakebed sediment layers. "You can see when it was really cold, it was mostly a grass- and sagebrush-dominated landscape," he explained, noting the presence of willow pollen, suggesting low, shrubby willows similar to those found in the Arctic today. The landscape during this period was also drier than it is now. Shuman utilizes ground-penetrating radar to map past lake shorelines, indicating that the region is currently experiencing its wettest conditions in at least the last 20,000 years. Furthermore, the late Pleistocene in this area was characterized by strong winds and significant dust accumulation. Glacial meltwater carried pulverized rock silt, which dried and was carried by the wind, eroding hollows in Wyoming, shaping dunes across the Great Plains, and depositing thick layers of glacial dust far into the Midwest. The author found it challenging to fully envision pronghorn, accustomed to modern snowstorms, navigating an ancient landscape even colder, drier, windier, and dustier than today’s.

In that harsh Pleistocene environment, pronghorn faced formidable predators beyond the elements. Fossil evidence indicates that species like Miracinonyx, the American cheetah, a 160-pound relative of the mountain lion adapted for pursuit, and the formidable American lion, one of the largest cats to have ever lived, along with the powerful Beringian wolf with its robust jaws and teeth, all preyed upon pronghorn. Isotope analysis of their fossilized remains confirms that these three species consumed pronghorn. These exceptionally preserved fossils are found in Natural Trap Cave, a vertical, bell-shaped cavern on the western flank of the Bighorn Mountains in northern Wyoming. The cave’s opening, an oval hole approximately 15 feet across, has served as a natural trap for millennia. Animals that stumbled into the opening and fell over 80 feet into the cave often perished from their injuries or starvation. The absence of scavengers and the cave’s stable 42-degree Fahrenheit temperature have preserved complete skeletons and even DNA, undisturbed by external elements.

Since 2014, Julie Meachen, a vertebrate paleontologist from Des Moines University, has led a research team at Natural Trap Cave. Her initial descent into the cavern, a daunting 80-foot rappel, revealed bones embedded in the walls. While researchers in the 1970s and 1980s had discovered remains of camels, cheetahs, horses, and even mammoths, the cave had remained largely unexplored for decades, recognized as a significant repository of fossilized life. Alongside the remains of Pleistocene lions, wolves, and bears, pronghorn fossils dating between 17,000 and 20,000 years old were found, morphologically 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, camels, and giant short-faced bears, some more than twice the size of present-day grizzlies. In the summer of 2024, Meachen’s team unearthed a mammoth scapula, ribs, and vertebrae, suggesting the presence of at least three mammoths that fell into the cave during the Pleistocene.

Todd Surovell, an archaeologist at the University of Wyoming specializing in hunter-gatherer societies, has studied mammoth sites and written extensively on late-Pleistocene extinctions. He shared a small Ziploc bag containing a walnut-sized fragment of mammoth ivory, smooth and creamy white with jagged brown ripples, explaining its significance as evidence of these colossal creatures’ presence. Surovell noted the abundance of Columbian mammoths, the largest mammoth species in the Americas, which ranged from Canada to Mexico along the front of the Rockies, confirming "just tons of mammoths." Picturing a 22,000-pound giant stripping grass with its trunk, its 16-foot tusks sweeping through the air while pronghorn cautiously navigated the terrain to avoid lurking predators, highlights the dramatic ecological interactions of that era, interactions that persisted for tens of thousands of years until an unknown force triggered the extinction of most of these large animals.

On a geological timescale, the 7,000-year transition from the depths of the ice age to the Holocene, the current epoch, occurred with remarkable swiftness. However, for pronghorn, these changes unfolded over hundreds of generations. Around 17,000 years ago, a gradual wobble in Earth’s axis, occurring on a 41,000-year cycle, began allowing more summer solar radiation to reach the planet. This initiated the melting of the ice caps. As reflective white ice retreated towards the poles, the darker exposed ground absorbed more solar heat, amplifying the warming trend. Paleoclimatologist Shuman referenced a textbook, Earth’s Climate: Past and Future, which detailed the end-Pleistocene warming and the scientific methods used to study it.

The melting ice caps released vast quantities of freshwater into the oceans, carrying sediment and dust, and consequently raising sea levels by approximately 360 feet. These massive freshwater influxes altered ocean currents and warmed the oceans, leading to the release of carbon dioxide. This increased atmospheric carbon dioxide concentration amplified the greenhouse effect, trapping solar heat and accelerating global warming. Shuman described this cascade of events: "This chain of orbital changes, ice sheet changes, dust and ocean changes, all causes carbon dioxide to go up and down." He emphasized that carbon dioxide "is probably the biggest single hammer on the system."

By approximately 10,000 years ago, atmospheric carbon dioxide levels had increased by over 40%, leading to a global temperature rise of 7 to 11 degrees Fahrenheit. Central North America became wetter, transforming arid grasslands into lusher environments, and forests began to advance northward. Pollen records indicate the flourishing of pine, spruce, and fir trees. While beneficial for arboreal growth, this ecological shift was not universally advantageous for megafauna. "A lot of the big things that used to be here just didn’t survive," Meachen observed. Of the numerous large mammals that inhabited Pleistocene North America, at least 59, and possibly more, went extinct, leaving only 26 species remaining today. One analysis suggests that 72% of large mammal species, from horses and mammoths to giant beavers and ground sloths, along with many predators, vanished from the continent.

Surovell noted a correlation: "The bigger you are, the more likely you are to go extinct. Very few small things go extinct." His 2009 co-authored analysis indicated that the majority of these extinctions likely occurred between 13,800 and 11,400 years ago, a brief interval in geological time. He further stated that subsequent research has only strengthened this evidence. The mass extinction of large land mammals remains a profound mystery, a subject of ongoing debate with proposed causes ranging from human influence to a possible asteroid impact or interspecies disease transmission. Nevertheless, scientists generally concur that abrupt climate change played a significant role in this dramatic decline in biodiversity.

Among the species that persisted, the pronghorn antelope stands out as a remarkably ancient inhabitant. Antilocaprids have inhabited the continent for more than four times the duration of cervids; the ancestors of deer, elk, moose, and caribou arrived in North America approximately 4.8 million years ago, while the ancestors of modern bovids, such as bison, bighorn sheep, and mountain goats, appeared a mere 2.5 million years ago. The modern pronghorn, the sole living descendant of the original Antilocaprids, is unique to North America, having evolved to thrive within its specific ecological niches. Christine Janis, professor emerita of ecology and evolutionary biology at Brown University and a renowned scholar of animal evolution and climate change, confirmed their resilience. She explained that pronghorn ancestors navigated earlier extinctions of ancient deer-like animals around 5 million years ago and survived alongside animals like horses and camels until the end of the Pleistocene, when these groups ultimately perished.

While the precise mechanisms of their survival remain a subject of study, several theories have emerged. Meachen highlighted their ability to subsist on minimal water and their capacity to consume dry, scrubby vegetation that other large herbivores, such as horses and bison, could not effectively utilize. Surovell added that the extinction of the American cheetah likely benefited the pronghorn by removing a significant predator. Janis credited the pronghorn’s high-crowned teeth, which extend well above the gumline, allowing for ample wear even when consuming gritty, low-growing browse throughout their lives. She also pointed to their small size, which enables a faster reproductive rate compared to larger animals. Unlike a large camel or mammoth that might produce a calf every few years, pronghorn typically give birth to two fawns each spring. Janis summarized the key to their survival: "Be small and be adaptable in your diet. That’s a good way to survive."

Pronghorn have demonstrated remarkable resilience through numerous environmental shifts, and further changes lie ahead. Global surface temperatures continue to break records year after year. The greenhouse gases being released into the atmosphere today are projected to induce a rate of global average temperature increase over the next 75 years that far surpasses the 7,000-year transition that ended the ice ages, melted ice sheets, thawed permafrost and glaciers, and transformed tundra into forests, leading to the extinction of so many large mammals. Shuman stated, "That’s the type of magnitude change we’re talking about, except it’s going to keep going into a warmer direction that’s still hard to imagine."

The future feels inherently precarious, both for pronghorn and for humanity. Planetary changes are occurring at a speed potentially unmatched since the asteroid impact that caused the extinction of the dinosaurs approximately 66 million years ago. The critical question is whether our own living systems can adapt to such rapid and profound alterations. As a resident of this region and the mother of two children born in Wyoming, contemplating this question is deeply unsettling. Nevertheless, studying the survival strategies of pronghorn has offered a shift in perspective. The thought of enduring the arid, treeless, and frigid conditions of the deepest ice ages is a sobering one. It is evident that increased precipitation in some areas has fostered the growth of forests and supported certain animal populations, including pronghorn, in the warmer modern climate. Earth’s history, spanning billions of years, is a testament to its dynamism and the continuous adjustment of living systems through diverse climates, from periods when Wyoming harbored palm trees and crocodiles to millennia locked in ice and back again. The planet’s inherent dynamism and the adaptive capacity of life are sources of wonder. Recognizing that humans, unlike many other animals, possess the ability to alter their diets and, much like pronghorn, can adapt to a range of climates and environments, even migrating to new habitats if necessary, offers a measure of hope.

When a 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 affected area. These survivors went on to birth new fawns and thrive on the new 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 attentiveness and gentle care, observing subtle shifts in the wind and the nuances of the air. Pronghorn exemplify the importance of deeply understanding one’s habitat and aligning personal patterns and behaviors with the forces of the land. They urge me to recognize changes in snowdrift patterns, to notice which plants emerge after a soaking thunderstorm, and to accept that each spring will present its own unique characteristics. They inspire me to teach my children to identify birdsong, to learn about the seasonal movements of animals, to breathe deeply, and to continue moving forward with steadfastness, their feet firmly planted on the Earth.