Category: Science

The Horse: The Epic History of Our Noble Companion by Wendy Williams is one of my favorite recent reads. The book is a fascinating mixture of geology, biology, and history. A great gift for anyone who rides, certainly.

Here are some excerpts to inspire you:

Horses are the stars of Ice Age art. Indeed, horses are the most frequently represented animal in the twenty-thousand-year period that preceded the advent of farming and what we call civilization.

contrary to popular belief, science has discovered that they are not “herd” animals. Instead of seeking safety in large numbers, horses live year-round in small groups called bands. Membership in these bands, which may consist of as few as three horses or as many as ten or so, is just as fluid as are the individual bonds, but there’s usually a central core of closely allied mares and their young offspring.

(Because of the stress of constant fighting with other males, stallions often live much shorter lives than mares.)

When I started researching free-roaming horses, I was astonished at their numbers—in the millions. I was also surprised by the variety of ecosystems where the horses not only live, but thrive. There may be more than a million free-ranging horses in the Australian outback alone

All over the American West, free-ranging horses roam in small bands. They even seem to do well in areas around Death Valley, one of the hottest and driest places on Earth. You would think that a species that can live in Death Valley would have trouble living in swamps and wetlands, but it turns out that they don’t. A little south of the Namibian desert, another population of horses lives in the Bot River delta of South Africa.

The book gives multiple examples of evolution in action:

consider the case of the sea-island horses who live on Canada’s Sable Island, a small harborless sandbar of an island located far out in the North Atlantic, about a ninety-minute plane flight east from Halifax, Nova Scotia. This tiny island, shaped like a crescent moon, is about thirty miles long and very narrow. Buffeted constantly by violent North Atlantic storms, this island seems an unlikely home for free-roaming horses, yet as many as 450 graze here, surviving by eating beach grass and sea peas. This sounds like a meager diet, but the horses, abandoned there by a Boston entrepreneur before the American Revolution, have endured for more than 250 years.

The only non-marine mammals on the island, the horses serve as a real-world laboratory of evolution. Over the centuries, they have become unique. Their pasterns are now so short that, from a distance, their lower legs look something like the legs of mountain goats. The pasterns of most horses are long and angled, allowing for plenty of spring in the horse’s step, which in turn allows for greater speed and stamina when a horse gallops at high speeds over an open plain. Long pasterns evolved as a survival strategy. But longer pasterns also carry an important disadvantage: the pastern’s fragile bones and vulnerable tendons can easily break or strain, laming the horse. Many a racehorse has ended his career because of this vulnerability. But on Sable Island, the horse does not have to run fast to escape predators. Instead, their enemy is deep sand and their worst “predators” are steep, treacherous sand dunes, some almost a thousand feet high, which the horses must climb in order to eat. These dunes provide some pretty dangerous footing for horses. On Sable Island a horse is much more likely to injure a leg while descending these steep dunes than by running along the island’s beaches. Still, a hungry horse must ascend and descend these obstacles. Consequently, evolution has made a clear choice, just as in the Camargue region. Sable Island horses have shorter, less vulnerable pasterns, giving them that goatlike look. Over 250 years, natural selection has opted for shorter pasterns, improving the horses’ ability to graze, thus improving the horses’ ability to live longer and produce more offspring. We often think of evolution as complicated, but in this case, the process is pretty easy to grasp.

The author covers some of the dynamism of the Earth’s climate:

Most likely, paleontologists suggest, the truth behind the extinction involves many factors. When the asteroid fell, the world was already changing. The great supercontinent of Pangaea had broken up and North and South America were slowly migrating west, creating an ever-widening Atlantic Ocean—an ocean that would become a major player in the appearance of humans and in the evolution of horses and in the flight paths of birds and in the pulsations of ice and rain and drought for the coming tens of millions of years. These long-term events, the results of our always-convulsive, seething-with-energy planet, were probably more influential in the appearance of horses and humans than the onetime crash of a mere mega-asteroid. … the Yale University paleontologist Chris Norris called the emphasis on disaster as a major evolutionary force “asteroid porn.”

His point is well-taken: the worldwide climate had been changing for 10 million years before the asteroid fell. The dinosaurs were no more enjoying a steady-state world before the asteroid impact than we are today.

It was hot. For a brief period, it was very hot, much hotter than when I visited. In fact, it was as though there was a sudden explosion of heat, as remarkable in its own way as the fall of the asteroid had been 10 million years earlier. Curiously, this explosion of heat also marks the appearance of Polecat Bench’s horses and primates. This was a time when temperatures in some places shot up by 6 or 8 degrees Celsius in a very short time period, lingered at those heights, then, almost as suddenly, dropped back down. The cause of this heat spike remains elusive, but it may have been due to large bursts of methane that bubbled up from the deep ocean. On temperature charts that track the rise and fall of heat throughout our planet’s history, the heat spike looks to me like the outline of the Eiffel Tower. The anomaly is officially called the Paleocene-Eocene Thermal Maximum, PETM for short, but I prefer to think of it as the Eiffel Tower of Heat, with its sharp lines of ascent and descent that mimic so closely the graceful lines of the Parisian landmark. It’s a weird event. And it’s doubly weird that both horses and primates may owe their existence, in part, to its existence: the spike marks the beginning of the Eocene, when not just horses and primates, but most modern mammal groups finally came into their own.

Just a few things that surprised me:

• North America, devoid of horses when the Europeans showed up to trash the place, has a rich fossil record of horses. Horses were here at least as recently as 30,000 years ago.
• Horse teeth keep pushing out for about 20 years.
• “The ten thousand or so varieties of grasses that cover Earth today take up an estimated 30 percent of our planet’s land surface.” (and grass is a relatively new plant)

More: Read The Horse: The Epic History of Our Noble Companion.