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Chapter Two

Evolving a Brain

Why do we need to know how brains are engineered? I mean, there they are, fully formed, and ready to go. Why not just “shut up and dance,” as the song says? The reason is that the way brains evolved eons ago tells us a lot about how they work today.

Equine brains are engineered to sense and interpret the equine world. Where’s the best grass? Which way is the water? Is it safe to lie down here? What’s that noise? Is my alpha mare concerned? But they are not designed to take in and interpret the human world, and that’s what we ask of them most often.

Not only do we expect them to understand the human world, we also expect them to understand us! Now, I don’t know about you, but even with a human brain I sometimes fail miserably to understand people. Truth be told, I’m not always that great at understanding myself. How can we expect horses to succeed at the task?

Brains—horse, human, or otherwise—are engineered through time in many ways. Some methods of brain design are more easily modified than others. In shaping equine behavior, we need to know which aspects of the brain can be changed and which must be accepted.

 Brains evolve first by natural selection, in which a mental ability helps individuals to survive and reproduce. For example, early horses who noticed peripheral movement quickly tended to stay alive. The physical structure of today’s brains is determined by environmental pressures that occurred millions of years ago. We can work around it somewhat, but we cannot eliminate or change it.

 Brains adjust through domestication, which is driven by artificial selection. Here, humans choose stallions and mares with certain traits to yield offspring who carry the same trait. Breeders can select for temperament and trainability, but often choose beauty, speed, or strength instead.

 Brains mature during development from birth to adulthood. The human brain develops for 25 years before it is fully mature, longer than most of us realize. In horses, the length of brain maturation to adulthood is unknown. Physical maturity in general takes five to seven years, depending on breed. Experiences during development alter the brain significantly, so the early training we provide to a horse is critical.

 Brains change physically throughout adulthood in response to daily learning. Every time you or your horse experience something important, new connections are formed among brain cells. With use, these connections form a persistent record in the brain. In addition, new neurons are born throughout adulthood.

Natural Selection

Bone and tooth fossils show that the earliest ancestors of today’s horse lived in North America 56 million years ago. The size of small dogs, they had wide-set eyes down near their noses and padded feet with several toes. Warm temperatures of the era had produced subtropical forest across most of the continent, and the lower leaves of those trees kept pre-horses fed and sheltered. Life was good.

But fast-forward 21 million years, when an Ice Age caused temperatures to drop. Polar ice caps formed, glaciers moved in, forests died, and prairies emerged—covered with hard ground, tough grass, open space, and predators. Pre-horses whose bodies could not withstand these new conditions died off. But those few individuals who happened to have warmer fur, bigger bodies, stronger feet, faster legs, and harder teeth survived. They reproduced, their offspring reproduced, and so on—altering the species’ bodies and brains over eons of time.

If you have a chance, try a speedy getaway across rough ground on soft padded feet and a bunch of cold toes. Not very fast, is it? So, through natural selection, the horse’s outside toes began to disappear. Today, the splint bones in our horses’ legs, the chestnuts above their knees, and the ergots on their fetlocks are vestiges of those ancient outside toes. Meanwhile, the central toes hardened and enlarged into hooves that could travel a long way on rigid surfaces.

Natural selection also streamlined the horse for speed, with longer-legged horses better able to survive and reproduce in the new conditions. The bones in equine legs became longer. The “knee” (or carpus) on a horse today is actually the equivalent of a human wrist. Everything below that carpus is the equivalent of a human hand with very long fingers. The horse’s ankle or fetlock corresponds to the large knuckles of your hand, where the fingers begin to protrude. With all this lengthening of equine bone came longer tendons. Today’s equine legs are lightning fast for running away, but length makes them fragile too. Long legs also lifted the horse’s head above the level of tall plains grasses—the better to notice predators lying in wait.

Brains Run the Show

With all of these evolutionary changes in the horse’s body, the brain’s sensory organs had to adapt. Peripheral motion vision and precise hearing tuned up so that important sights or sounds—the rustle of a predator’s movement through grass, for instance—would be noticed instantly. Smell became critical for safety from predators and navigation to water. Motor coordination and fast-twitch muscles became vital for escape. These increases in sensitivity were built partly into the eyes, ears, nose, and muscles. But they are even more apparent in the brain tissue where sensory signals arrive for interpretation and in the hard wiring that carries action commands to various destinations in the brain.

The internal operation of brain cells adapted too. Fatty tissue was produced to surround the long tail (or axon) of each neuron, so it could transmit information faster. (Neurons are a type of brain cell that transmit functional information.) In today’s horse, some axons are 10 feet long, stretching from the brain and looping around through the body. The fastest can transmit messages up to 394 feet per second. That’s nearly 250 miles an hour! Glial (“GLEE-ull”) cells—the brain’s janitors—multiplied to keep neurons healthy. The neural ability to form connections became faster and more efficient (fig. 2.1). So did the brain’s ability to kill off unused connections that would only interfere with the learning process.

2.1 Neurons transmit electrical impulses through equine and human brains. The dendrites of one neuron send electricity through its axon. Axon terminals then transmit that information to the dendrites of the next cell.

The brain adapted to collect glucose from food more efficiently, because brains hog glucose for fuel. The human brain represents 2% of your total body weight but uses 20% of your body’s glucose. Equine brains are downright gluttonous—they comprise only two-tenths of a percent of the horse’s total body weight but use 25% of the glucose. Too much glucose can harm our bodies—both equine and human—but too little harms our brains. That’s why we get confused when our blood sugar is too low.

Hard-Wiring for Safety

When dangerous sensory signals were detected on the prairie, a horse couldn’t twiddle his hooves deciding what to do. He had to run first and be alive to ask questions later. To manage that requirement, the equine brain evolved to connect perception directly to action. A nerve signal comes from the eye to the visual processing area of the brain, for example, and the equine brain instantly sends that signal to the motor control area with the command to RUN (fig. 2.2 A). These processing areas are in the surface, or cortex, of the brain. It all happens unconsciously.

2.2 A The horse’s brain detects sights at the visual cortex, then sends the new information to the motor cortex for immediate action.

2.2 B The human brain also detects sights at the visual cortex. But it sends that information to the prefrontal cortex for analysis and evaluation before the motor cortex springs into action.

The wiring between perception and action in the human brain is quite different. A nerve signal comes from our eyes to the visual cortex at the back of our brain, and is usually diverted to a slow path that meanders over to the prefrontal cortex just behind our forehead. There, an unconscious analysis is undertaken: “What have I seen? Have I seen that before? What does it mean? What should I do? Which option is best? Why? Did I have lunch yet? Oh…whoops, let’s pay attention… Hmm, option 17c has worked in the past. Let’s try that one again.” Finally, action kicks in—long after a lion would have punctured an equine throat and gobbled half a leg (fig. 2.2 B).

Innate Instincts

The process of natural selection over millions of years forms the hard wiring of a brain—its major pathways and structures. Evolution always lags behind the present day. So the human brain still functions according to its ability to hunt meat and gather berries, keep its body warm and dry, find mates in the savannah, and try to prevent the children from being eaten by lions. It doesn’t matter that today we drive to the grocery store instead of spearing a wildebeest for dinner, meet potential mates online, and try to prevent the children from being shot in their schools.

Some pathways make stops here and there along the route to their brain destinations—and often, these stops occur at places where the path ended a few million years ago. When scientists see an abandoned way station like that, we have evidence that the brain used to work differently than it does now. For instance, in 2018 researchers found links in the human brain between areas for navigation and smell. People no longer need to smell their way to water, but at one time that ability was so critical for survival that our brain structures changed physically to account for it.

Most psychologists agree that the initial stages of romantic attraction are hard-wired. You don’t turn the process on, and you can’t just flip a switch to turn it off. The feelings are involuntary. But that doesn’t mean we have no recourse. We can work around attraction by learning to notice and identify it, pausing to think carefully about its implications, listening to Mr. or Ms. Perfect’s point of view, and removing ourselves from awkward situations. The feelings are still there, but we don’t have to act on them.

Shying is a good example of hard-wired behavior in horses. Equine brains evolved to whirl and bolt when potential danger occurs. Horses are captive to the naturally selected aspects of their brains, just as we are to ours. In addition, horses have far less ability to manage their hard-wired behavior than humans do. They’re super-smart but do not have the prefrontal cortex to control their instincts fully. We cannot expect a horse to smell a bear a few feet away and simply walk on.

This, by the way, is not a hypothetical example. Aspen, a furry dun pony belonging to a friend, tended to shy out in the back forty. One area near a thicket of willows was especially difficult for her to negotiate. She was convinced of danger there, tightening her muscles, doing the quickstep as if on Dancing with the Stars, and opening her eyes wider every time she approached. In frustration, her owner hired a trainer to get Aspen past this foolishness.

The trainer hopped on one fall day and rode Aspen to the thicket, where she pulled her usual shenanigans. He insisted she move closer to the bushes and, trembling, she eventually agreed. Just about then, a black bear bounded out of his cover, moving on all fours straight toward Aspen—who took off hell bent for election. Everyone learned some lessons: Sometimes it really is best to listen to the horse. And don’t poke the bear!

So do we have to allow every horse to spin out from under us whenever a leaf wiggles? Of course not. We can teach the horse to get to know a frightening area over time, to shy with smaller movements, to slow down and investigate after shying, to trust our leadership. We can teach ourselves to distinguish between equine nerves and true fear. We can overcome our frustration—after all, the horse is behaving in a perfectly natural way. Horses shy just like car passengers slam their useless brake feet into the floorboards and gasp for air when expecting a crash. It’s the brain’s involuntary method of staying alive.

Social Dynamics

Because of their distant past, horses are strongly social animals with herd instincts. They respond to their buddies at all times. We humans fail to notice much of this subtle interaction, and it weakens when we are around. But left on their own, horses rely on group perception, learn by imitation, seek leadership from dominant guides, and soothe themselves through social contact.

As the horse evolved to survive predators on open grasslands, his brain became more dependent on activity within the group. Imagine 10 horses grazing in a field that is familiar to them. By nature, they will adopt slightly different positions with their bodies aimed this way and that for greater surveillance. Although their heads are usually down, each horse pays attention to the others. If the most sensitive horse glances up to check a noise, the others cock an eye or ear toward him. If one horse startles, the group looks in that direction immediately. To stay safe, they need each other.

When removed from the group, horses transfer their need for leadership from a dominant equine to a human. So, in the absence of a higher-ranking horse, your mount is going to look to you for help. He doesn’t need a friend or a follower—he needs you to be his leader.

Social behavior among horses is partly learned but largely innate. Brain scientists in 2018 found that mammalian brains are hard wired to regulate the rank hierarchies, group status, social vocalization, and peer observation that horses use all the time. To train well, we need to understand these evolutionary motives.

Evolution’s Behavioral Tendencies

Because of their need to escape predators, horses are innately afraid of being restricted or confined. Tying, for example, needs to be taught in a gradual gentle way to overcome the horse’s natural fear. Blocking the horse’s side view in narrow passageways causes trouble —and, unknowingly, people do it all the time. At least 35 million years of evolution tells an equine brain that the dark, restricted, metal box of a trailer spells D-E-A-T-H. A horse who balks at these practices is not being ornery. He’s being a horse.

We all know that horses are attuned to unexpected sights and sounds. But many people don’t realize that the least obvious of these are the most likely to startle the horse: short rapid movements and low-volume sounds. Predators did not announce their presence in advance—they tried to hide. If you’ve ever seen a non-horse person try to “hide” from a horse so as not to bother him, you know what I mean. Once while I was giving a lesson, a visitor tried to hide her Labrador Retriever under the bleachers in an indoor arena. Every horse in the ring flipped out. Once the dog was in plain view, they settled. Hiding from a horse is impossible, and the very act of attempting to remain unseen and unheard unnerves the horse much more than a serene open approach.

Some of the most critical brain differences between horses and humans are wrought by the distinctions between predators and their prey. Horses (along with rabbits, deer, cattle, and many other species) are prey animals— food for predators. Their brains evolved to notice tiny movements instantly, hightail it out of there with no analysis, and live in groups for safety. Prey animals are easily identified by sideward-facing eyes that survey a wide horizontal range for potential danger.

Predators have forward-facing eyes. Their brains evolved for visual focus, depth perception, stalking, and killing. These include lions, wolves, cats, dogs, and um (how can I say this gently?)…humans. You and I are predators, and every horse knows it with one glance at our close-set eyes. The fact that horses allow us to work with them at all—let alone straddle their backs—is a testament to their generosity, curiosity, and domestication. But we do well to remember that the horse’s brain is still hard-wired by evolution to fear us.

Fear of isolation is another by-product of equine evolution that we can’t change. Safety lies in the group. Even super-chill horses tend to be more nervous when they are alone. Equine misbehavior caused by fear can often be relieved by introducing another horse. Give the worried animal the comfort of a buddy—a horse who walks quietly into a trailer, a horse who relaxes on trail rides, a horse who has seen scary objects but survived to tell the tale.

Domestication

Today’s species of horse, equus caballus, includes all breeds and represents the domesticated version of its forest and grassland ancestors. Technically, domestication refers to artificial selection, which has occurred for at least 6,000 years. Key breeding characteristics for the purpose of taming a wild animal are calmness, ability to learn, submission to captivity, and willingness to allow human contact. By selecting mares and stallions with these traits, people have produced horses who are much easier to train than their undomesticated counterparts would be.

Many people assume that “wild” horses today are undomesticated. That’s not accurate. Some are feral individuals who have lived without much human contact but are descended from domesticated ancestors. They live in bands on their own, but are not truly “wild.” Until recently, the Przewalski horse of Mongolia was thought to be the only remaining undomesticated horse. But DNA evidence now shows that even this breed descends from domesticated ancestors.

Many allegedly “wild” horses are abandoned. During the 2008 recession in the United States, for example, some impoverished horse owners turned their animals loose in undeveloped areas to fend for themselves. A few lucky survivors formed groups that are sometimes referred to as “wild” even though they grew up in stalls and enjoyed years of training.

After several thousand generations of domestication, we now have horses whose bodies and brains are mostly naturally selected, but whose behavioral traits of calmness and acquiescence are largely artificially selected. Variation among breeds is also a feature of artificial selection. The American Thoroughbred, for example, is bred to be light, long, lean, and agile—perfect for speed. Belgian Warmbloods are bred to be bulky, thick-muscled, wide, and slow—great for power. Along with these physical traits come differences in temperament, with the flighty nervous racehorse contrasting the stolid reliable Belgian. Within each breed there are individual differences, of course.

Today’s Brain

Throughout evolution, brains have become bigger. Yet brain function in both horses and humans is determined far more by neural connection than absolute size. According to the Internet, the horse’s brain is the size of a walnut. Or a human fist. Three baseballs. Next thing ya know, they’ll be likening it to a peanut or a watermelon. Sounds like some facts are in order.

Pop a human brain out of its skull and you have a 3-pound lump of squishy tofu that’s 75% water. The average horse’s brain has the same consistency but weighs 1 pound 5 ounces, not quite half the weight of its human counterpart. A basketball weighs the same, as does the brain of a six-month-old human baby. In terms of size, the adult human brain is about 4 inches high, 6 inches wide, and 7 inches long. The tissue of both the human and horse brain is especially dense in some areas, often corresponding to “structures” that are identified in diagrams.

The horse’s brain is about the volume of a grapefruit. In shape, the grapefruit is elongated and partly squashed. It’s lumpy and bumpy but measures about 4 inches high, 4 inches side to side, and 6 inches front to back. It rests on a 45-degree angle pointing downward rather than sitting level as a human brain does.

Most important for function, the horse’s brain contains slightly over 1 billion neurons, far fewer than the human brain’s 86 billion. Depending on its type, each neuron can accept up to 10,000 connections. These connections are the magic behind equine perception, learning, emotion, and athleticism.

Brain Change through Maturation and Learning

One of the linchpins to any form of animal training—or human learning, for that matter—is to identify what can be changed and what cannot be changed. We’ve seen that evolution drives certain equine behaviors that are innate and physiological. By respecting them, we reduce the horse’s fear and can then alter more malleable aspects of his brain.

Brain connections are built by daily experience. Few people realize just how physical a process learning is. When a foal takes that first step toward you, a new physical connection within a group of brain cells is formed. It’s weak, it will disappear if it’s not repeated, and it’s prone to mistakes. But every time the fledgling connection is used, it becomes stronger. The foal’s second step forward strengthens it, tomorrow’s positive approach reinforces it, and so on. Eventually you have built a brand new network of connected neurons inside your foal’s brain that forms an initial bond.

That one physical connection is the basis for everything the foal will do in the human world. You will build on it, little by little, until this baby trots at your shoulder, halts on a slack lead when your feet stop moving, follows verbal commands, accepts a saddle and rider, learns to jump, wins a world championship, retires with you to the trails, and eventually enters the old-age pasture.

Neural connections form throughout all of life, so you can continue to shape your horse’s brain—and your own—until the day one of you leaves this earth behind. Pause for a moment to think about the immensity of that power. And the responsibility that comes with it. You are shaping your horse’s physical brain, and he is shaping yours. That is an extraordinary—almost supernatural—ability. Cherish it.

Reflex Action

If human perception and action are mediated by thought, you might wonder how we so rapidly avoid pain. Automatic reflex actions are responsible for that—and the brain does not control them. Next time you touch a hot stove burner (please do not try this at home!), notice how your arm instantaneously pulls away. This action occurs at the level of the spinal cord, before the pain signal has time to reach the brain. No thought is involved. Horses experience reflex actions when they shake flies off their skin, shiver in the cold, cough, swallow, suckle, or blink.

Hard-Wired Fears

Natural selection causes horses to fear:

 restriction

 confinement

 darkness or narrow passages

 sudden movements

 unusual sounds

 predators

 isolation from the group