Twelve hundred years ago, a Mongol chieftain wrote a poem to celebrate his war horse Dapple. Apparently he and the horse cared deeply for each other, reading each other’s minds in battle and, when not in action, sharing the chieftain’s tent. This is one of the oldest texts about horses. The chieftain’s poem has been followed by a seemingly endless collection of opinions, facts, and emotional expressions about horses from scientific papers to dressage instruction manuals to racing forms to Black Beauty. The most recent contribution to the subject is Stephen Budiansky’s The Nature of Horses: Exploring Equine Evolution, Intelligence, and Behavior. Why has it taken 1200 years to achieve such clarity and insight?

Budiansky’s book is different from most books about Equus caballus, or indeed about any other domestic animal, since it is not much concerned with the services provided by the animal, or with helping owners and trainers extract those services. Any animal is more interesting than the sum of the tricks it can perform, and Budiansky touches on training very lightly. When he does, it is usually to explain why horses will do certain things but not others. He tells us, for instance, why horses don’t like to back up. Their wide-angle vision has a pie-shaped blind spot to the rear, and backing up is “not a good idea for a highly social, prey animal that cannot see directly behind itself—where a predator or a dominant member of the herd may be lurking.”

This is typical of Budiansky’s ability to describe the world from the horse’s perspective. On spooking, for instance, Budiansky writes: “Some horses seem almost to enjoy scaring themselves. They will snort, or tense up and stumble, and then react with fright to the snort or the stumble…. The horse then begins to anticipate the fright it is preparing to give itself.”

Budiansky has gathered much information from his close relations with horses. His own horse, whose name is not revealed, serves as a respected colleague. This horse demonstrated, among other things, that horses sometimes rely on their sense of smell even though they rarely show much interest in odors. Once when the horse and Budiansky became separated from a hunt, the horse put his nose to the earth and, like a dog, successfully trailed his companions over much-used paths from which all visual clues had been obliterated.

Budiansky has splendid scientific credentials—he was the US editor of Nature—and he is particularly helpful in showing how much misinformation about horses has traditionally been circulated, not only among lay people but among scientists as well. Early in his book, for instance, he corrects an inaccurate version of horse evolution that nearly everyone seems to have acquired during childhood, a story in which the Eocene ur-horse that emerged some four million years ago grew bigger and better and stronger and faster, just as any animal would want to do, until it reached the height and speed of a horse today.

Not quite, says Budiansky, pointing out that evolution does not represent a straight-line progression and does not have a purpose or a goal. Nor are modern horses improvements on their tiny forebears, any more than they are “better,” say, than modern dik-diks, the pygmy antelopes which, as small, territorial browsers in the African forests, occupy an ecological niche similar to the niche the ur-horse once filled.

Another common fallacy holds that all modern animals, including horses, underwent major transitions during their millions of years of evolution. Actually, some animals—squirrels, for instance—have changed very little over the last twenty million years. Why did horses change so drastically? Not to escape predators, as many people believe, and not to keep warm, although the Ice Age had started by the time the process was under way. Horses changed, Budiansky explains, because their food changed—not only what it was but where it grew. In contrast, the diet of squirrels stayed the same.

As the Ice Age advanced, the sheltering forests gave way to open plains. Many forest herbivores were forced to shift their diet from leaves to grass. On the plains, horses found themselves in stiff competition with cattle, sheep, and goats—animals with rumens or second stomachs—which could more efficiently break down the large amounts of enhanced cellulose that the besieged grasses quickly developed for their own protection. Without the advantage of rumens, horses lost the competition for the most nourishing grass and were forced to eat coarse, poor fodder that few other animals could use. Because each bite contained so little energy, a horse had to eat huge amounts to get any strength from its food. And in this fact lies the explanation of why horses grew big. The larger the body, the more slowly it burns energy. To illustrate, Budiansky contrasts a hummingbird to a lion. Small and fast-burning, the hummingbird eats constantly while the big, slow-burning lion sleeps. Like hummingbirds, horses eat almost constantly, but the energy value of their food is so low that only because they are big and therefore slow-burning like lions can they afford to eat it.


As horses became larger their faces grew long, again because of their new food. In the forests the short-faced ur-horses surely ate with their heads raised, alert for danger as they browsed the very leaves that screened them. But on the steppes, the ur-horses’ larger descendants ate in full view with their heads down and their eyes buried in grass, making it easy for predators to sneak up on them. But as horses’ faces lengthened, their eyes rose above the grass, so they could watch for danger while grazing.

Horses also developed new social systems. In the forests, the habits of the ur-horses probably resembled those of dik-diks, with the little ur-stallions closely guarding individual territories where roaming, non-territorial ur-mares could join them. But on the open plains, the habits of horses changed to resemble those of, say, bison, who range so widely that they can’t hold territories. Perhaps a stallion couldn’t control land, but he could still control the reproduction of several mares. Instead of guarding a place where mares lived, he’d guard the mares themselves, rounding them up and bringing them wherever he went. Thus, in the horse tribe, wives replaced territory as property, and herds began, and with them came new social systems. To enhance cooperation, encourage experienced leadership, and promote peace, horses developed hierarchies. Then, like many other social animals, including people, they also developed social castes. A study found “a significant correlation between the rank order of foals and the rank order of their dams; the more aggressive foals were consistently at the top of the heap.” Today, when horses form herds, whether they run wild or live on horse farms, the affairs of a herd tend to be managed by the dominant members, who for the most part act as leaders and decision-makers. Low-ranking horses usually defer.

Budiansky provides a delicious example of the etiquette that horses sometimes display at races. “Although any horse may initiate movement in feral bands,” he writes,

a low-ranking individual who starts to lead the way will usually soon stop and allow a dominant horse to pass ahead…. Handicappers have frequently noted that some seemingly slower horses will consistently beat horses that have recorded considerably faster speeds; it seems plausible that this is at least in part a reflection of subtle assertions of dominance that horses (especially mares) instinctively defer to when the herd is on the move.

But horses don’t always observe this particular courtesy. When horses stampede, says Budiansky, “usually the most nervous mares…are consistently out in front. Perhaps the question is whether a horse race more resembles a purposeful herd movement or a stampede.” Anyone who could ask the horses that question would win a fortune at the track.

We expect high-ranking animals to be leaders. Here again, oversimplification has left us unprepared for the contribution of low-ranking horses. Few people realize that it was not the most dominant horses but the meekest horses who eventually inherited the earth and saved their species from extinction, becoming the ancestors of virtually all Equus caballus alive today.

Again, the event was an outcome of a change in climate. When the Ice Age ended, trees reclaimed the land from the grasses, which began to dwindle. Because horses by then had become grassland animals and were dependent on grass, they too began to disappear. Ten thousand years ago they became extinct in the New World, their original home, and they would have vanished entirely had they not already extended their range across the Bering Land Bridge into Eurasia. There, in Eastern Europe, a small remnant population of survivors saved themselves and their species by discovering the crops grown on Neolithic farms.

Customarily we humans claim credit for domesticating animals, a feat we allegedly managed to achieve by fooling the various herds and packs into thinking we were their dominant members. Here again Budiansky must re-educate us. We didn’t domesticate animals, he says. Rather, animals domesticated themselves. They found our settlements and realized that our crops (or in the case of wolves, our refuse) could be a source of food. So they tried as best they could to live among us. “Some were killed and eaten,” Budiansky explains,

but for every cow or sheep or horse killed, many more flourished on the crops they robbed from our fields, and on the incidental protection they gained from other predators in the proximity of human habitations. Like the starlings, mice and rats, and chimney swifts that invade our homes today for the food and shelter that are a by-product of our domestic habits, those forebears of our domestic stock took the initiative. We followed.

According to Budiansky, early domestication of horses took place in the Ukraine, where, as farmers destroyed the boldest, most aggressive horses while ignoring the shy and the meek, normal husbandry became a negative evolutionary force. Low-status horses lived to reproduce, passing on their propensities for mildness. The process, which occurs in most tamed species, is known as neoteny—the domesticated animal’s retention through adulthood of certain characteristics that its wild forebears displayed only in their youth. Thus domestic horses retain certain characteristics of wild foals, not only their milder dispositions but also their leggy bodies and their delicate, gracile heads. Anyone who has dealt with the wild species that are related to horses will appreciate the neoteny of domestic horses because virtually no one can handle wild adults. Zebras, for instance, furiously resent all our efforts to coerce them. A captive zebra, a stallion whom this reviewer met in Florida, almost bit off his keeper’s penis right through the keeper’s heavy clothes. Undoubtedly in the zebra’s eyes the unfortunate man was acting like a rival—but not, evidently, like a rival of intimidating rank.


Learning what forces have created an animal, what twists and turns the animal has taken on its evolutionary road, enhances our appreciation of the species. We realize we haven’t understood these creatures that we thought we knew so well. Nowhere do we more clearly see what horses really are and how little we really know them than when we encounter Budiansky’s discussion of their mental abilities.

According to popular belief, horses are stupid. And so, perhaps, they would be if they were people. Anyone who performed like a horse in trying to make his way through a small maze or solve a simple problem would indeed be considered stupid. One horse was no more successful than a tropical fish, a guinea pig, or an octopus when asked to distinguish between an open feed container and a container covered with cloth, although all four animals eventually learned the difference.

Interestingly, dogs do well on such problem-solving tests. But this doesn’t mean that dogs are smarter than horses. It simply means that the minds of these two very different animals are prepared for very different eventualities. Dogs are carnivores, and carnivores eat things that fight back or try to escape. Thus each meal presents a problem that the carnivore must solve. In contrast, the food of grazing animals offers no such challenge. It simply waits peacefully, ready to go down their throats. Grazing animals face many difficulties in life, but solving a problem before each meal isn’t among them. Hence, unlike carnivores, grazing animals aren’t particularly well equipped for problem-solving tests.

Nevertheless, we human beings for the most part ignore the many different mental requirements of the many different species. Regarding animals as if they were merely lesser versions of ourselves, we envision a ladder-like model of mental ability, a model that places people on the top rung with other animals assigned to different rungs below—chimps and dolphins immediately beneath us, say, and clams and worms on the bottom.

The ladder theory gives rise to some peculiar notions. Certain so-called experts have actually stated that the intelligence of animals compares to that of human children. We often hear, for instance, that a wolf has the intelligence of a three-year-old child. Yet a wolf is in no sense comparable, mentally, to a human child of any age. It is difficult, for instance, to imagine a pack of preschoolers surviving a winter in the Arctic wilds.

We would understand an animal’s mental achievements more clearly, suggests Budiansky, if we “consider all the functions that an animal’s brain is called upon to perform before we pass judgement on its mental ranking in the animal kingdom.” To illustrate, he points to an American folk hero, the absent-minded professor. Equipped with a big brain, the professor is so preoccupied with his own abstract thoughts that he doesn’t remember his address or recognize his family. He trips over his own feet. Still, he embodies what we most admire about ourselves, namely our propensity to generate abstract ideas, sometimes at the expense of other abilities such as observation, memory, and coordination. Many of us relegate such skills almost to the levels of bodily functions—instinctive, hardly worth noticing, and certainly nothing to boast about.

Like the professor, a horse also has a big brain. Like the professor, the horse also has plenty of mental ability. But unlike the professor, who spends much of his mental power on theories, the horse spends his on more practical matters. Among these is the immensely challenging task of poising his large, heavy body on four long, tapered legs and moving it from place to place.

Understandably, a horse’s motor skills seem trivial to us, especially if our standard is our own locomotion, which entails nothing more taxing than falling forward onto alternating feet. But perhaps we can begin to understand a horse’s achievement when we learn of the extreme difficulty experienced by a team of engineers attempting to design a horse-like robot. The task proved virtually impossible. The difficulties and failures were “testimony to the complexity of the neural processes involved in [a horse’s] locomotion,” says Budiansky. It proved much easier to build a dog robot which could follow a scent or give an alarm than a horse robot “that uses vision and tactile feedback to make its four legs canter smoothly over rough ground.”

Needless to say, in addition to their superb locomotion, horses display other mental abilities in generous measure. For example, horses have excellent memories. A horse trained to get a food reward upon identifying one of many pairs of unrelated symbols remembered the correct pair a year later. Long-term memory greatly benefits any wide-ranging animal who exploits seasonal food sources and returns at irregular intervals to the terrain visited months or years before. Elephants, who, like horses, range widely for rough fodder, are famous for their memories.

Finally, horses are excellent observers. Budiansky tells the story of Clever Hans, the nineteenth-century German horse who allegedly solved math problems by tapping the answers with his hoof. What Hans actually did, of course, was to tap until he spied a very subtle signal unconsciously provided by his interrogator, a signal telling him to stop. The local absent-minded professors—scientists and mathematicians all—were understandably skeptical, and flocked to see if the claims for Hans were factual. Hans performed convincingly, and the distinguished gentlemen were duly impressed. But at last Hans was questioned by someone who didn’t know the answers. Without the signal, he couldn’t respond and was soon exposed. Predictably, the public was outraged, and to this day Hans’s name remains synonymous with fraud. Nobody understood that this horse was a far better observer than the foremost scientists and mathematicians of his day. Somehow, for all their intellectual abilities, these men missed every cue that Hans unfailingly noticed—the subtle signals that told him when to stop tapping his foot.

From such evidence, Budiansky draws an impressive picture of a horse’s mental strength. We won’t think of horses as stupid again any time soon. What’s more, we realize that Budiansky’s picture of equine ability applies to other animals too. Many animals, in short, have copious mental abilities that we either ignore or disparage for the simple reason that we don’t share them.

The Nature of Horses has no faults to my knowledge, although I would have liked to see more on the little ur-horse, which Budiansky refers to by its scientific name, Hyracotherium. Intriguingly, the prefix hyraco designates the Hyrax order, Hyracoideas, while the Greek theria (meaning wild beasts) is a zoologist’s name for placental mammals. Hyraxes (sometimes called conies, dassies, or rock rabbits), are relatives of the hoofed animals, and today are small and rather rare, surviving only in Africa and along the Mediterranean coast. But back in the Eocene, some 50 million years ago, the proliferation of hyraxes resembled that of dinosaurs in the famous Age of Dinosaurs. During the later and less celebrated Age of Hyraxes, these animals came in all shapes and sizes including mighty 600-pounders, so there was a hyrax of some description or another in virtually every plant-eating niche. Then along came the modern hoofed animals with their sophisticated digestive systems that won them the competition for vegetable fodder, forcing the primitive hyraxes to evolve new bodies or else to go extinct. Was a hyrax the ur-horse Hyracotherium?

However, an account of the ur-horse would not necessarily enhance this superb book. Readers will enjoy The Nature of Horses for its insights and its boldly stated, forward-looking views. Here, for example, is some of Budiansky’s informative discussion of a horse’s vocalizations.

Attempts to assign precise semantic meanings to animal sounds have long been a preoccupation of both animal behaviorists and animal lovers. Both have been guilty of anthropomorphism. The animal lover’s sentimental desire to believe that his pets are talking to him is easy enough to understand. That scientists for years should have pursued the same red herring is a symptom of a more subtle failing…. Animals were said to have mating calls, food calls, warning calls, threat calls, and so on.

Given that horses make four basic sounds, the nicker, the blow, the squeal, and the whinny, Budiansky points out that we should ask what the sounds accomplish rather than what they mean. A horse’s nicker may not have evolved as a sound but rather as a purr, a vibration, made by the foal to be felt within the mother’s body. Thus it signals appeasement and submission. The horse’s blow is like a bark, fixing the attention of other group members. The squeal, used to its greatest effect in contests between stallions, serves as a weapon for a mock battle, settled not by actual fighting but by the squeal itself. And as for the whinny,

Like a dog’s howl, a whinny is a long-distance communication signal…acoustically optimized for carrying across long distances. In forests, signals that are tonal and relatively high pitched…usually travel best…. In open environments, a signal that is lower and “buzzy” is more efficient. These are indeed the characteristics of a horse’s whinny, and common experience proves how far that sound can travel.

Whether naturalists or cowboys, whether bluegrass aristocrats or race-track touts, whether distinguished academics or little girls gone horse-crazy, all readers with an interest in these large, remarkable animals are bound to be fascinated by Budiansky’s knowledge, by his original thinking, by the authority with which he says what many other scientists lack the wisdom or the courage to say, and by the ferocity and tenderness of his voice. Budiansky enjoys science. He never once neglects the accuracy and impartiality that the discipline demands. But his feeling for horses is so great that he can’t hide it. And so, as his readers absorb his knowledge about horses, they may also acquire his respect for them.

This Issue

May 15, 1997