In the era when mammoths roamed, ancient horses thrived in North America. These equines, which went extinct alongside other megafauna like the Smilodon, have left us with no direct descendants. Following their extinction, horses were absent from the continent for thousands of years until settlers reintroduced domesticated varieties. This raises the question: what did these long-lost horses actually look like?

During my last move, the U-Haul truck we rented featured a striking image of what appeared to be a zebra. However, it was actually an artistic interpretation of the Hagerman horse, whose remains have been extensively uncovered in Idaho. Initially, I mistook it for a zebra due to its bold black and white stripes. This piqued my curiosity about whether Ice Age horses in America might have exhibited similar striped patterns, solid colors, or a mix of earthy tones and patterns. (I sketched a rough concept of a possible brown-and-striped pattern for the Hagerman Horse.)

In this discussion, I will explore three avenues through which we can speculate about the appearance of North America's Pleistocene horses: dental structure, genetic insights, and ancient artistic representations.

North America is often regarded as a cradle for horse evolution, hosting a remarkable diversity of horse species over time. For example, Wyoming is rich in fossils of Hyracotherium, recognized as one of the earliest known horses, sometimes referred to as “eohippus.” In the past, smaller, three-toed grazers coexisted with formidable predators like the hellpig and the nimravids. More recently, the Ice Age featured horses of the genus Equus, resembling modern horses, while larger, unconnected species roamed areas like Canada and Texas. This continent has long been a sanctuary for horses, which later spread globally. However, the last of these ancient horses vanished around the same time as other Ice Age megafauna, severing the lineage of North American horses.

Despite their extinction, wild horses exist across the American landscape today. These modern equines share a lineage with horses brought over by European settlers, quickly adapting to their new environment and becoming integral to various Indigenous cultures. Today’s wild horses symbolize the American West, while beneath their hooves lie the fossilized remains of their ancient ancestors. Although today’s horses are descendants of those first domesticated in Eurasia, they share a close relationship with their North American predecessors within the Equus genus.

Currently, several species of Equus exist, including horses, donkeys, and zebras. However, we lack paleoart depicting North American horses, leaving us to speculate on their appearance. Paleontologists and artists face considerable challenges when reconstructing the appearance of these ancient creatures.

One method of inquiry involves examining the teeth of Pleistocene Equus, which can provide valuable information regarding their species.

The image above shows a fossil horse tooth from the Pleistocene era. The characteristics of the surface, which interacted with food, can help identify the species. The Florida Museum of Natural History has a comparative diagram that illustrates the differences in modern horse teeth, including those of today’s Equus species. Remarkably, the fossil teeth closely resemble those of zebras, which are known for their striking stripes. The museum’s representation of Equus simplicidens features bold black and white stripes, akin to the depiction that caught my attention on the U-Haul truck.

The evidence from teeth suggests that the prehistoric Equus horses of North America may have exhibited stripes. I am eager to compare these fossils with those of ancient European horses to determine if they were more akin to zebras or to the modern domestic horses they eventually spawned.

While the analysis of teeth presents a compelling narrative, the situation is more nuanced. European cave art features horses that appear different from zebras, often showcasing a dun coloration rather than stripes.

Another avenue of investigation involves examining preserved genes in horse fossils, which can inform us about ancient coloration. Fortunately, recent DNA analysis indicates that North American horses interbred with Eurasian counterparts, particularly through the Bering Land Bridge, prior to domestication and during the Late Pleistocene. This suggests that these horses may not have been entirely distinct species; genetic exchanges hint at a more interconnected history.

This revelation is significant. It implies that Equus simplicidens, also known as the Hagerman horse, and Equus ferus, the wild horse lineage from Eurasia, may actually belong to the same species or be much more closely related than previously believed.

A third avenue to gain insights into ancient horse pigmentation is through prehistoric human artistry. Cave art across Europe prominently features horses, many of which display a dun coloration with distinctive markings. While some artwork suggests variations in color and pattern, none exhibit the striking black and white stripes characteristic of zebras.

Some researchers propose that horses worldwide may have been striped until the advent of domestication, which favored solid colors for easier identification in the landscape. Horses are relatively recent additions to domesticated species, with most experts agreeing on their domestication occurring around 5,000 to 6,000 years ago. However, the cave paintings, which predate this period, depict wild horses.

In summary, it is probable that Ice Age horses in North America had stripes, at least dorsal stripes and leg markings typical of dun-colored horses. Given the interbreeding between North American and Eurasian Equus, it is reasonable to assume they bore similarities, though regional variations likely existed. While certainty is elusive, scientific findings allow us to make informed conjectures. I believe that these ancient horses did not resemble zebras with full-body stripes. Their close European relatives, who frequently interbred during the Pleistocene, likely displayed dun coats with fewer stripes than a zebra.

The watercolor above was a gift for my horse-loving sister, accompanying the fossil horse tooth previously mentioned. I depicted the horse with distinct leg stripes, but my attempts at subtler markings on the head faded into the overall shading. Though this artistic interpretation is speculative, future research may clarify the appearance of Pleistocene horses. Genetic analysis has already shed light on the coat patterns of Eurasian horses, and it has revealed that North American Equus horses were not isolated species but rather part of a broader genetic exchange between continents.

As we explore the genetic history of Ice Age horses and examine the rich cave art depicting Eurasian horses, I contend that the portrayal of American Pleistocene horses as zebra-like with bold black-and-white stripes is likely misguided. They likely had stripes, particularly on their legs, but the idea of them having full-body zebra stripes might be an overstatement.

Future research into the coat color genes in North American horse fossils could ultimately answer whether Ice Age horses had zebra-like stripes.